Welcome to Pragmatic.
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audiobook download. We'll talk more about their sponsors during the show. I'm your host,
John Chidjie, and I'm joined today by my co-host, Vic Hudson. How you doing, Vic?
I'm good, John.
Fantastic. Well, I'm excited before we get started, too, that I'm on my new audio setup,
I say new because it's brand spanking new. Actually, brand spanking new, is that an Australianism
or is, do you know what that may mean when I say that?
I've heard it before. It's commonly used over here.
Yeah, good. Probably not quite as much as it used to
be but you're definitely not the first person I've ever heard.
That's a relief. I just, I worry sometimes that I speak sometimes in some Australianism.
So anyway, there you go.
Just check, just checking, just checking, litmus test.
Anyway, so yeah, I now have,
thanks to Dan Benjamin of 5x5
and his absolutely brilliant podcasting equipment guide
brought over from the days of Hive Logic.
And of course, more recently updated for 5x5
in Jim Metzendorf as well.
I did a bit of research
and I had been using an Audio Technica
ATR 2100 USB microphone,
but I've upgraded that now to a Heil PR40,
which is a dynamic microphone.
Excuse me.
Sorry about that.
And-
- No, you're okay.
- And I'm also running that through an Onyx Blackjack,
which is made by Mackie, and that's a USB interface.
And it's got a 24-bit ADC in it,
which is better than the 16-bit that came in the ATR2100.
The frequency response on the Heil is much better,
as well as the dynamic range.
And I've done some test recording and it is just lovely.
So hopefully, hopefully this,
the podcast is that little bit slightly nicer on your ears.
In addition to that, I've also,
I'm also going to be starting to edit in Logic Pro X,
which seems to be the most favored podcast editing tool
out there at the moment.
So yeah, all about upgrades at the moment.
Mind you, I'm still using the original shock mount,
isn't designed for it and the pop filter and boom arm so and the boom arm is struggling because this
mic is something like twice as heavy as the other one but anyway so there you go that's inside
podcasting enough of that okay so just another a bunch of quick reminders once again yes we are
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working on the latest beta of Yosemite. Yikes. Anyway, that's fine. Yeah, I know I'm running
a beta operating system. I think the GM just went out actually.
[laughs]
It did last night.
Yeah, anyway. Well, that's not available in public. The public beta 4 went out,
which I'm sure is very similar. But in any case, whatever. That's fine.
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doing a regular recording, same time every week. So if you want to tune in live, you now can,
and it's the same time every week. Okay, right, that's enough preamble. So today we're going to
talk about radio, specifically amateur radio. And one of the reasons that I want
to talk about this is because it's something that's very near and dear to
my heart. Historically it's been a big part of my life, it's what got me into
electrical engineering in the first place and set me on the path that I'm on
to now. And I dare say that if I didn't get into radio that I wouldn't be,
probably wouldn't be podcasting right now, so you probably wouldn't be hearing my voice.
So if you like the domino effect and that sort of thing, well you know this
This is one of the big dominoes in my life, professionally and personally.
So it's a big deal to me and I wanted to talk about it because there's a lot of people out
there that say, "Oh yeah, amateur radio or ham radio.
Yeah, yeah, I know what that is."
And I actually don't really know all the different aspects of it, what's interesting about it.
So I thought it'd be worth talking about.
Now I have talked about radio previously on episode five, which is the next ubiquitous
thing.
episode if you are interested in learning a little bit more about Marconi
and the basics of broadcast but we'll quickly touch on some of that now just
as a quick refresher as to like what radio is and so on but before I do that
just a little bit about you know my history with radio so I actually started
on CB radio when I was 14 years old you know with a very cheap radio it was a
Oh dear, very cheap. It was a Uniden PC55 and I picked it up really cheap and I
didn't have a decent antenna. I built my own antenna. I had an old piece of
coax that was the wrong kind so it was 75 ohm coax. It should have been 50 ohm
coax and unfortunately that caused lots of problems with my poor little radio.
Not understanding then what I do now, you know, I killed that radio. So you know
It had been six months time I had to get another one.
Anyway, so I moved on from that and got better radios
and learned more, built better antennas
and so on and so forth.
Pulled all of my pocket money and so on into it
and so on and so forth, met lots of interesting people.
And then I decided in my first year of university
that I wanted to become an amateur radio operator.
So I had two choices at that point.
I could have have waited till the end of my degree
and gotten the advanced theory gratis.
So if you show up with your advanced degree,
sorry, advanced degree, got.
If you show up with an engineering degree,
electrical engineering degree,
and you waive that at the right people,
they would give you a pass on the advanced theory exam
without you having to sit it.
- Ah.
- Which was kind of nice.
- Yeah.
- But me being impatient and well,
hey, who would have thought I was impatient back then,
just like I am now.
Hey, there you go.
Anyway, being impatient, I decided, nope, not gonna wait,
so I studied and sat my advanced theory exam anyway,
even my first year of uni,
because I couldn't be bothered waiting, I didn't wanna wait.
Also had to sit the regulations,
which I note, I actually passed my advanced theory
on the first sitting,
but I actually failed my regs on the first sitting.
Yeah, whoops, I failed at something, God.
Anyway, so yeah, I had to sit my regulations a second time.
Whoops.
Anyway, I also went for, back in the day,
back in those times, that was '94.
Back at that time, Morse code was a requirement.
So there were two Morse code.
There was a novice and there was advanced.
And novice was five words a minute, send receive.
And advanced was 10 words a minute, send receive.
- Got it.
- So I, in order to get what they call
the full call amateur radio operator license,
full call unrestricted, then you had to sit advanced theory, regs and advanced morse,
which was 10 words a minute.
So I also learned the didars and again failed on my first attempt at 10 words a minute.
Most people are smart and they start at 5 and they work their way up to 10, but me,
no, stupid me.
Anyway, I sat on my second to go and I did a good job.
And yeah, absolutely blitzed on my second attempt.
I walked in there and read the sentence off
and you know, guy shook my hand and said, "Nice."
So there you go.
No mistakes, flawless.
Anyway, on the second attempt, first attempt.
So as I often mention, and some people have said,
"Hey, it's bingo time."
John said the word Nortel on the podcast.
So there you go.
Here we go again.
So yes, I worked for Nortel Networks
and I was in the RF hardware design group
between '99 and 2001.
I worked on the HF modernization project for Boeing
for between 2001, 2003, so two years on that.
More recently in telemetry systems,
which are based in, you know,
which is radio-based telemetry,
the long reach sewer telemetry system design,
the Douglas Northern Water Treatment Plants,
Townsville telemetry system design.
And I also did an option study for the Turong pipeline,
which is the pipeline that runs from,
well, it doesn't matter.
Anyway, for the Turong Power Station,
about 120 kilometer long water pipeline for the cooling water and that
telemetry system did the telemetry option study on that. So that's
notice my background experience. So a real quick recap of what radio is. So
radio refers to our radio RF is radio frequency energy and that refers to an
electromagnetic wave and depending upon and all radio waves essentially sine
waves and those sine waves, travel sine waves, and those sine waves depending upon their period and
therefore their frequency depends on you know the band what we call the band, the frequency band,
that you transmit information over. So ranging from about 3 hertz up to 300 gigahertz. Now the
formula for a wave is v equals f lambda which is velocity equals frequency times wavelength
Therefore from the frequency you can figure out the wavelength and the wavelength of that 3 Hertz is
100,000 kilometers which is pretty big and 300 gigahertz is one millimeter. So there's a huge
variety of wavelengths and that that's important when it comes to antenna design, which we'll get to later
but anyway
So EM waves travel through space. They're not dependent on air. They're not compression waves
So anyway, the velocity of electromagnetic waves is the speed of light, which is 3 times 10 to the 8 meters per second, which is, you know,
a bit zippy.
Electromagnetic waves exist perpendicular to each other, so you'll have in the
E-plane and the H-plane, what they refer to as the E and the H-plane.
So in the E-plane you'll have the electric, say, and in the H-plane you'll have the magnetic field, and each field sort of
follows the other, and it's sort of hard to describe that, but one that's
it's hard to describe but anyway I'm going to link to eventually put a
presentation up on the site that I did for a company I worked for. But
electromagnetic waves only exist where they both exist so if you kill the
electric field on the magnetic field you'll kill the EM wave which is of
course the title of the first episode of Pragmatic was Faraday's cage so this
Michael Faraday came up with this idea of a cage that you could use to kill the
electric field and hence the electromagnetic waves would stop
passing through that cage. So anything inside the cage would not
radiate out, anything outside the cage could not radiate in through
electromagnetic waves, which was useful for testing and so on and so forth.
When we talk about radio we talk about different frequencies for different
purposes and a lot of it comes to do with permeability. And permeability not
in the magnetic sense, but permeability in the sense of how much it'll penetrate
physical objects. And I say penetrate, you know, it's partly penetrate, it's
partly bend. Because, you know, wave theory, you know, wave theory suggests
that as waves pass through, pass an edge, that they can actually diffract and bend
around that edge. And not just that, as they travel through mediums of different...
well, it's a good way to think of it as like density, but it's not density. But anyway,
it's a good thing that is it you can actually bend a radio signal through it
through through a through charged particles for example and an example of
that is the ionosphere which we'll get to in a minute. So the idea is that
waves don't just travel in straight lines you can get them to bend. You can't get them to
bend too much and the higher frequency you go the less likely they are to bend
so lower frequency signals are better for that which is one of the reasons
that AM radio started at low frequencies so between about 535 kilohertz to a
about 1.7 megahertz that's where AM radio sits but the problem with that of
course is that you know AM radio because you've got such a small snippet of
spectrum you don't have a massive bandwidth that you can encode
information on like audio so as a result if you want to have lots of radio
stations you got each one's gonna have a very narrow frequency that they operate
on which means that the quality of the audio is gonna be much less yeah the
other problem of course down that that region of the spectrum is that you get a
lot of atmospheric noise so when there's a lightning strike you get lots of low
frequency EM pulses. I mean you're gonna get like background galactic radiation
no matter where you are what frequency you're at you're just gonna get it.
It does tend to travel further than FM though doesn't it? Yes exactly and that's
why yes and that's why they chose it because what happens is it tends to bend
with the earth a lot more so whereas FM is high frequency and therefore doesn't.
Well it does a little bit that doesn't really. So the propagation of EM waves is
dependent upon their frequency through the atmosphere. So the most coveted
parts of the mobile phone spectrum traditionally have been the low
frequency. So in Australia for example Telstra have access to the low
frequency so 700 megahertz to 850 megahertz spectrum. So anything under 1
gigahertz is going to get much better building penetration because of its low
frequency. The way to think about building penetration is that if you look
at the wavelength and then you look at the size of an aperture like a window, think of
how much of that energy in terms of its wavelength could actually penetrate the window if that
electromagnetic wave was pointed approximately at the window. So the idea is that the lower
the frequency, you will get a much larger probability that energy will get in through
that aperture than you're going to get if it's a much higher frequency signal, which
which is going to be far more precisely directed, if that makes any sense.
Yeah.
Such that the sum total amount of energy is going to be much less.
And once the wavelength is so small, it comes down to just luck, like reflections and just
pure chance as to whether or not you get a signal.
But assuming you're not living inside Faraday's gauge, let's say.
Anyhow.
So those I was saying about Telstra and the low frequencies, they went for that stuff
because you know it's got far better. It was the old analog network that they
then shifted across to what they call NextG which is running CDMA and well I
say CDMA it's it's LTE but anyway these days. So anyway I guess what I'm getting
at is that as you go higher up in frequency that's when things start to go
wrong in that respect but then of course things get better for things like
satellite where you want them to pass through the atmosphere unmolested so
without any ionospheric interference. So that's all trade-offs. Once you go really
really high frequency of course electromagnetic waves cease to be
interpreted that way because then we start reaching visible spectrum.
But not talking about that, that's another story. So radio waves also
have another problem it's called the inverse square law because essentially
electromagnetic waves emanate as a bubble and in theory there's a point
there's a point in space that they call an isotropic radiator. An
isotropic radiator is a theoretical antenna which is simply a point in space
that radiates equally in all directions. So if you can imagine that, radiating
equally in all directions, that's expanding like a perfect sphere. So the
idea is that at any distance, let's say a distance from the center point, if you
are distance X from the center point and then you go a distance of 2x from the
center point then the overall amount of energy at any one point will be 1/4
because it's 1 over 2 squared. If you go three times the distance X then it'll be
1 over 3 squared or a ninth. That's the inverse square law. Simply because the
same amount of energy is being spread over a much larger area. So you can't
you can't escape that. Which is why of course, you know, beyond the fact that the isotropic
radiator doesn't actually exist, you know, the simplest form of an antenna that you can build
is actually a dipole. And a dipole has 2.14 dB of gain over an isotropic radiator. So if you assume
that an isotropic radiator is a theoretical, you know, starting point, and that's all well and good,
you understand that that's why you want directional antennas, because you want to be able to focus
that energy in one specific direction, which is the whole point of an antenna.
Well, it's the whole point of a directional antenna. You don't want to waste signal
going in directions that you don't ever care to receive it at anyway. Exactly right. Yes, precisely.
So unless of course you're building an omnidirectional antenna, which is like a vertical
antenna, you know, the idea with that of course is that that'll transmit and receive equally in all
directions but you know the truth the truth is that you know that's boring but
we'll talk about it anyway. All right so getting the getting the signal to from
the radio to the antenna we use something I call a transmission line
and transmission lines sole purpose is to not lose power so to take the signal
that's generated at the radio and then transfer that to the antenna without
losing any of that signal. Obviously there's no such thing as a perfect
transmission line, but there's essentially three most common transmission lines in use.
The first one is the good old fashioned ladder line.
Now I'm assuming that you know what I'm talking about when I say ladder line.
I think so.
Old TV sets?
Yeah, old TV sets.
They have this thing, it's like two black wires and they were joined every so often
with a bit of thick black plastic.
And if you looked at it and you held it up, it looked like a ladder.
In later years, they would encapsulate the entire thing.
were just sometimes made out of clear plastic but more often than not it was black.
Anyway, ladder line is what's referred to as a balanced transmission line
and it was favored for quite some time but the truth is it's very prone to
interference. So the next most common type is coaxial cable, that's an
unbalanced transmission line. The idea is that you have a common conductor in the
center, an insulator and then you wrap that around with a shield and that
shield is then wrapped in an insulator itself. So coaxial cable is by far and
the most common transmission line for connecting antennas to radios. When you
go up higher in frequency that starts to fall apart and you're far better off
going with something that's far more cool, something called waveguide.
Waveguides, what they do is they only really are effective in terms of their
physical size once you get up to multiple gigahertz of wavelength.
Waveguides essentially bounce the radio signal from one end to the other.
fascinating idea but it actually does work. So to utilize electromagnetic waves
for carrying information, you have to understand a concept of
resonance. So if I have a radio, the radio is a source of radio energy. That
RF energy is oscillating at a certain frequency. Let's say
it's CB radio, you know HFCB radio which operates at 27 megahertz.
So that's going to oscillate at whatever frequency, 27 MHz.
And in order for you to, yeah, funny I just said it, didn't I?
The funny thing is, the best analogy is the tuning fork.
Now have you ever done that experiment at school where you've got two identical tuning
forks and you hold one up in the air, you tap the other one to get it to vibrate and
then you hold them right next to each other?
I have not.
I've heard about it though.
Okay, well the idea is that what happens is the sound compression waves from the one that's
vibrating, what they do is they travel through the air to the one you're
holding next to it and it starts to vibrate. They call that a sympathetic
vibration or resonance. And it's supposed to match right? Yes that's right and
that's because that's the natural frequency of vibration of that tuning
fork. It's exactly the same thing with an antenna except of course with
electromagnetic waves. So what you do is you tune, I'm doing
air quotes, tune, your antenna, to a specific frequency to get the maximum amount of gain
out of that antenna. Because if it's not in tune, what will happen is you're going to
get power reflected back to the radio. So the idea is, think of the power transfer as
if I've got 10 watts in my radio and I have a transmission line going out to an antenna,
if that antenna is off by some percent, then I won't deliver 10 watts directly to the antenna.
I'm going to lose some of my transmission line, of course, but I'm going to get power
reflected back from my antenna back into the radio.
And that's a bad thing, because if you're, especially with silicon, because of silicon
it doesn't like the heat, so all that power that's not being dissipated because of a mismatch,
that's bad.
I mean, sorry.
You'll burn out the radio.
You will.
And that's exactly what happened with my first CB radio, if you recall, you know, about 15,
20 minutes ago when we started, I said, I had the wrong coax, I built my own antenna,
I had no idea what I was doing,
and I destroyed my first radio.
I blew the final transistors
because the final stage transistor amplifies.
Because what was happening was I had such a bad mismatch,
all a lot of power was being directed back.
I was supposed to be delivering,
I don't know, one watt, five watt radio.
I forget which, what it was.
I think it was a five watt radio.
And of which I'd be lucky if one watt
was actually getting out.
So, of the antenna, 'cause it wasn't tuned,
it wasn't matched,
and it was the wrong bloody transmission line.
It was just a joke.
And that's okay.
I was 14 and I was still learning.
I learned the hard way.
Anyway.
So when we measure signal and loss,
we measure it in decibels,
which is a ratio typically of power.
So, you know, one milliwatt, for example,
be referenced as the reference for what's typically referred
to as DBM and a DBM is essentially a power measurement.
So we'll say, okay, well, I've got a 20,
I've got a five watt radio.
my antenna gives me three,
so 20, so 20 watts,
let's go with one milliwatt
'cause the numbers are in front of me.
I'm not gonna do this in my head at four in the morning.
So one milliwatt radio is a zero DBM source.
So if I've got a zero DBM source
and I've got a three DB gain antenna,
then I'm gonna get a total of, you know,
three DBs worth of power output,
which I can then convert back into milliwatts if I want to.
And the reason we work in DB is that,
It's very helpful for other things.
So when I talk about gain,
I'll be talking about gain in decibels,
power, typically in DBM.
Okay.
- So that gives you a common scale.
- Yes, exactly.
Everything's normalized onto a common scale.
That's right.
Okay.
So antenna polarization, vertical, horizontal.
So if you have a vertical antenna,
then essentially what you're doing is you're taking a dipole,
which is essentially a straight line.
The idea of a dipole is that you have a half wavelength.
So let's say that your 27 megahertz of wavelength
is around about 10 meters long.
So half of that is five meters.
So you cut that in half again.
So you've got two quarter wavelengths
and they're fed in the center with your coaxial cable
through a device called a ballon,
which is a balanced to unbalanced transformer.
if you're doing it right. Well, I say if you're doing it right. Anyway, and the
point is that that particular design is the most basic antenna, but what you want
to do if you want to go vertical is you want to turn that on its end and what
you can do is you can use the ground as a mirror. So you chop off the bottom half
of the antenna and you have a quarter wavelength above the ground and that's
vertical. So you'll see a vertical antennas all over the place. You'll see
them on cars, you know, everywhere. Well, maybe you won't see them as
often on cars these days but you know those are vertical antennas. Now the
most basic form is a quarter wavelength but there's other ones like this 3/8
wave, 5/8 wave, you can load these things up I'm not going to go into all that
detail about those sorts of antennas. I just want to do the basics and then
we'll get into amateur radio. So anyway so that's vertical polarization.
Horizontal polarization you know well that should be obvious is that you've
got the antenna let's say it's a dipole and it's mounted horizontally above the
ground. Everything's relative to the ground of course in at the moment. So
So why is this important? It's important to understand because if you've got a vertical
antenna and you're going to another vertical antenna then you're going to have a polarization
match. If you have a horizontal going to a vertical antenna or vice versa you are going
to have a polarization mismatch. And a polarization mismatch can cost you 20 dBs worth of energy.
That's quite a lot. So to overcome the problem of waves bending and mutating and doing all
that good and bad stuff, if you're doing line of sight transmission you want to go polarization
to polarization. So let's say I'm on one side of town, you're on the other side of town, direct line
of sight, you want to go vertical to vertical or horizontal to horizontal if you can to get the
maximum signal. If you're going via ionospheric propagation where things get bent out of shape
and twisted around, well that's probably not so big a deal. Although it probably could gain you
a few decibels here and there. The truth is though if you've got a television broadcast station you
You don't have any of that.
So what you're gonna do is you don't know
whether or not the TV antenna is gonna be vertically
or horizontally polarized.
So what are you gonna do?
Because those little rabbit ears on the TV sets
could be at whatever angle you choose.
Usually it's some diagonal angle relative to the earth.
So what do you do?
And they came up with this idea of circular polarization,
actually, which is also used in space transmission
'cause space has no concept of ground.
There's no up or down or left or right
or any of that stuff, right?
You're just in space.
Anyway, yeah, so circular polarization is essentially a rotating EM wavefront and that
is so hard to describe in words, I'm going to leave it there, but just trust me it is.
So you can have two kinds, left-hand circular, right-hand circular, and a variant of circular
polarization is elliptical polarization.
Same idea, it's just that the, essentially the X and Y axes of the wavefront are somewhat
squished. Anyway, same kind of idea. Left hand circular, right hand circular
polarization insofar as if you get a mismatch. So if you've got LCP
transmission going to an RCP antenna you're gonna lose 20 dB and vice versa.
So of course you know you can't win right no matter what you do but the
difference is if you go from an LCP or an RCP to a vertical or horizontally
polarized antenna you only lose three decibels. Yeah. And that's
what you're going for. Yeah, exactly. That's not too bad.
3dB is half power. So that's pretty good. Makes it ideal for
space and for broadcast applications, which is why
circular polarizes the way they go. Yes.
At the dB scale, it's logarithmic, right?
Correct.
So when you when you say you're going down from 20 to three,
that's a lot more significant than just the integer values
would imply.
Exactly. It's huge. 20 dB is massive, a massive, massive amount of loss.
So the highest gain Yagis that you'll get, you know,
are only going to give you 15, 16 dB a gain.
So losing 20 dB is just horribly bad,
which is why people that are serious in radio, in amateur radio,
what they'll do is they'll have a horizontal and vertically polarized antenna
such that they can switch polarizations to get the maximum amount of power,
because you don't know which one it's going to be.
And there's some antennas, some amateur radios
will even have, you know,
have circularly polarized antennas.
- And this is why you see antenna arrays.
- Absolutely.
Oh yeah, that's just one reason.
There's antenna arrays is a whole other thing,
but yeah, that's absolutely true.
So, all right.
I don't want to go too much more into that,
but just a little heads up,
when we measure gain from an antenna,
what we're doing is we're measuring
We're measuring the maximum amount of gain when you plot it on the H and the E plane
and that's the maximum amount of power as measured at a distance from a center point.
Center point is usually the feed point or in the case of an isotropic radio which doesn't
exist it's that point source.
So a lot of antennas are measured against the isotropic radiator which kind of sucks
because that's a BS measurement.
So if I have an antenna and I say yeah it's got 2.14 dB of gain over isotropic you're
like, yeah, great. That's a dipole. Yeah. Okay, good. I mean,
what does that actually mean? It doesn't mean anything. So when
people you quote an antenna, you say, I'm buying this antenna,
it's great. It's got 10 dB of gain. Oh, really? 10 dBi or 10
dBd? Because it makes a big difference. Well, it makes a
2.14 dB difference. Yeah. So, you know, you'll often find that
these, you know, the sales pitches are almost always in dBi.
Because it sounds better. You know, whereas the reality is
that if you put a dipole up
and you put up this competing Yagi, let's say,
you're only gonna see an improvement of 8 dB of gain
because you're gonna get 2 dB for free
because it's a dipole compared to isotropic.
So just something to keep in mind
if you're buying an Antenna.
Anyway.
All right, talked about that.
Grounded dependence,
I'm not gonna talk about standing wave ratio.
I've talked about Yagis.
Okay, so Yagi, what is a Yagi?
Okay, so Mr. Yagi, Mr. Yuda.
So technically the full name is,
'cause it was a collaborative effort, is the Yagi Yuda.
But Mr. Yuda, unfortunately, his name got dropped off
for whatever reason, people just call it Yagi.
Anyway, Yagis are essentially the highest gain
linear antenna that you can get
without building like a parabolic dish.
And the way they work is you'll have a feed element,
sometimes called the driven element,
or a driver, and that will be your dipole.
And that'll resonate at whatever frequency
you want to get the maximum amount of gain at.
Then you'll have one element behind it,
which is slightly longer, and that's called the reflector.
Some Yagis will have two reflectors,
but it's one of those laws of diminishing returns.
They found that by adding more reflectors behind that,
you didn't get an appreciable improvement
in your front to back ratio.
So anyway, then in front of that,
the driven element, you'll have a bunch of director elements
and the directors are slightly smaller
than your driver element.
The spacing is of course critical.
So there's a bunch of formulas to figure that out,
what the spacing is between the elements.
And of course, once you get past about 10 director elements,
you know, it gets to the point of diminishing returns
where you can keep adding more,
it just confuses the radiation pattern,
you get reducing gain.
Like every director you add the first three-
- You're introducing noise.
- Yeah, exactly.
You're distorting the pattern so much
you're not getting appreciable improvements in gain. So all this radio energy is being bent
forwards and reflected from the back. So the ratio of power from what comes off the back lobe versus
the front lobe is called the front to back ratio. There's all other all sorts of other measures like
side rejection and all sorts of other things. The whole point is that you're trying to maximize the
amount of forward gain that you get out of the antenna by bending the electromagnetic waves
forward. It's a very cool idea, works very well, but you'll see Yagis all over the place. They're
very very common. So whenever you see an antenna that looks like a...
well essentially... I don't know, what does it look like? It's hard to describe. I'm trying to think of
an analogy of what these things actually look like. You've got a long boom which is, you know,
usually made out of steel. You can have your arguments with conductive and non-conductive
booms. It's a different set of equations for each. But anyway, and then you have a bunch of
of much smaller conductive bits of metal.
And they'll be spaced out across it.
And that's it really.
It's hard to describe what it looks like.
I guess it looks a little bit like a hairbrush
that's got spikes on either side.
Do you know what I'm talking about?
- Yeah.
- Cool.
- Old school TV antennas.
- Yeah, exactly.
And so if you look at any old TV antenna,
you will see a Yagi.
And also--
- Ariel in the UK.
- Ariel, exactly.
Yeah, that's true, TV aerials.
However, there's a big caveat on that.
Yeah, the Yagis, no, they're not.
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Okay, so I said TV antennas, they're Yagi's,
but they weren't.
What I mean is that the problem with a Yagi
is that they're very fixed frequency.
So once you vary too much from the center frequency,
they tend to lose a lot of gain.
and that's obviously not what you want.
TV is spread over a massive area.
You know, it's down, starts at hundreds of megahertz,
hundred megahertz goes up very close
to the gigahertz range.
It's a huge band, huge range of wavelengths.
I mean, you're literally starting down like 50 centimeters
and you're ending up around about the,
oh God, here I am doing math in my head
on the top of my head.
Let's just say it's a huge, huge variation.
You cannot design a Yagi that has a useful gain
such a wide frequency range. In 1957, a couple of bright people crunched some
really mind-bending mathematics and came up with the idea of a log periodic.
Now I absolutely love log periodics because I looked at the math and it's
just, it's beautiful. I mean as mathematics goes, you know, if you're into
that sort of thing I guess. But look, I'm just saying, really cool. So a guy called
R.H. Duhamel, I do not know the first name, sorry,
and D.E. Isbell.
I came up with the idea of a log-periodic array,
such that it will give you wide bandwidth,
but high directionality.
So, and how you can tell log-periodics,
if you've got to look closely,
is that what they do is they'll start off with,
it looks like a reflector element,
and then they taper off very quickly
down to a director element,
but they taper off kind of like a triangle.
I mean, it's not exactly a triangle,
obviously it's logarithmic,
but you know, it looks a bit like that.
Whereas with a Yagi, you'll have a wider rear element,
a slightly narrower driven element,
then all your directors will be pretty much the same size.
Whereas a log periodic,
it's more of a progression down
to a finer point at the front.
If you look really closely,
you'll see on a log periodic,
that it's not like a Yagi whereby all of the elements
are actually physically continuous.
So what you'll get is along the boom,
is you'll have on a log periodic,
is you'll have one half of the element on the lower side
and the other side will be essentially isolated
from each other.
So they're not electrically connected.
And then along the course of the boom,
you'll see a zigzag pattern,
whereby each half of the preceding element
is fed across to the other side of the boom
of the element in front in a zigzag pattern to the front,
loop at the front, zigzag to the back,
and then you feed at the back.
Or you can feed front end or back fed, doesn't matter.
Point is, it's the alternating cross feed.
And what that does is it creates a,
as the resonant frequency changes,
what it does is it increases the relative impedance
of the section of the antenna towards the front
the back based on the frequency so that the active driven point changes in distance along
the boom of the antenna based on frequency. It is so cool it's not funny. Well, I would
- I don't know, sorry. I like this stuff. Anyway, so what you'll often find is that
the LogPeriodic itself needs a bit of help on the extremes. So what do they do? A TV
antenna you will often find has an extra feature. It's not just a log periodic, it's got a few
Yagi features as well. So they'll have a log periodic in the center of the antenna and
they'll have a larger reflector element at the back, which is a Yagi feature, and they'll
have a few smaller, much smaller director elements at the front. So that's referred
to as a log Yagi because, well, it's a log periodic and it's a Yagi Yuta, therefore it's
a Log Yagi. And that's almost all television antennas are, the higher gain ones. So they
cover a wide frequency range, plus they've got a mixture of the best of both. They're
a hybrid antenna. Some of them have even got what they call a corner reflector. And corner
reflectors are these little sort of fan things that go up either side of the log periodic
element. And they're designed to drag in more antenna, more antenna, drag in more antenna,
No, drag in more radio energy from above and below.
Anyway, all right.
That's enough of the coolness.
So I'm just, I talk quickly about parabolic dishes,
parabolas, of course, you know, radio energy or light,
whatever it might be, they'll hit the parabola,
they'll reflect into a common focus focal point.
One of the things that people often forget about
is that there's multiple ways
that you can actually mount these things.
You can have axial front feed
or you can have offset, off-axis offset feeds.
There's another method, which is a castor grain
and it's sort of like a, there's a reflector
and you've actually, you go, you hit the parabola,
you come back out, you hit another reflector
and then you go back to another secondary focal point.
Anyway, it's sort of hard to explain.
And then there's the Gregorian one,
which the idea is that you use a convex
you use a concave secondary reflector and that will then refocus the energy back to
a surface point on the actual dish that you have to feed.
But irrespective of how it's done, parabolic dishes are brilliant at higher frequencies.
At lower frequencies they suck because they're huge.
Got it.
Okay.
I swear we're getting close to talking about amateur radio anytime.
Okay, so atmospheric propagation absolutely have to talk about this in order for a lot of the stuff in Amateur Radio to make any sense.
Well, as far as I'm concerned, the cool stuff to make sense. I say cool stuff because I find it cool.
Yeah, whatever. Maybe other people don't, but I do.
Okay, so the idea is that there's a few layers in the Earth's atmosphere.
There's the troposphere, and above that you start going into the ionospheric layers.
The ionosphere essentially are layers of the Earth's atmosphere that consist of charged particles.
And as the sun hits them, they charge the particles,
and they then act like a mirror for electromagnetic waves
between certain frequency range.
And the layers of the ionosphere are lettered.
So you've got D layer, E, F1, F2,
are the most common ones in radio propagation,
or what I call, sorry, ionospheric propagation.
So the D layer is 70 kilometers up,
F-layers 120, sorry, E-layers 120, F1 is 200,
and the F2-layers 300 to 400 kilometers,
so it's quite way out.
And the point is that as the sun goes up,
it charges all the way down to the bottom.
As the sun goes down, the charge begins to dissipate,
and that exposes the outer layers.
Now, why that matters is the angle
that the radio waves hit it.
So the ones that are closer to the ground,
therefore, you'll end up with much less propagation
as a result, because the mirror is closer
the ground but as that mirror goes out after the Sun goes down you'll start to
get ionospheric propagation from much further away which is why on radio
signals they'll broadcast out from one point like I am radio and during the day
you'll only hear local stations but at nighttime you'll hear stations from much
much further away and that's because Sun goes down the lower ionospheric layers
discharge and you start to get a reflections from further away but anyway
Cool. Yeah, it is kind of cool. I always wondered why that was. Yeah, all about the ionosphere,
which is kind of cool. And that means of course that you can intentionally skip signals, and that's
why some people refer to it as skip. You can skip signals between the Earth and the ionosphere all
around the world. And unfortunately a lot of it has to do with sunspots. A lot of people see
sunspots as a bad thing, but if you're on a radio, sunspots are like your friend. Because if you get
sunspots then what will happen is that those big waves of radiation will charge up the ionosphere
and that'll create patterns in the atmosphere that give you a propagation path between certain
locations. Bouncing it off the earth is the easier part especially if you live near the coastline
because when you're near the coastline, well the ocean is a very good conductor. So if you bounce
it from your sea, if your antenna bounces off the ionosphere and then comes back down again on an
ocean it's very likely to skip back up again and basically bounce around the world. So in order to
to take advantage of that sort of skip you really need a directional antenna.
And Yagi is by far the most common.
And at one point I was running a 6 element Starduster which is a 27MHz CB radio antenna
and I was running on a single sideband modulation, well technically the lowest sideband anyway,
I'm not going to go into modulation methods, that's a whole other podcast.
And my crowning achievements were two things.
One was I reached Oregon.
And of course, this is before the internet.
Anyway, and so I was talking to some people in Oregon.
I would regularly talk to Hawaii.
And after a while, there was one time I had a particularly lucky bit of skip where I heard
my own echo.
In other words, my signal traveled the entire way around the world.
And once you take your finger off the key, you hear your own echo, which is so cool.
That would be cool.
It was very cool.
Because of course, the time delay it takes for even the speed of light to travel around
the world, anyone that's talked on a long distance phone between continents will know
this.
And Skype of course suffers from it as well.
So yeah, cool stuff.
And of course all done with no wires.
See look Ma, no wires.
Okay, I'm not going to talk about franal zones, modulation methods, I'm not going to talk
about that.
I'm not going to talk about Shannon's Theorem.
So a few little things, things like repeaters.
Now people, you may have heard of repeaters.
The idea is that if I'm on a higher frequency and I want to talk to someone and there's
a mountain or some physical barrier between the two of us, how do I talk to them?
If I can't talk directly because I'm on a higher frequency, the signal won't bend, it's
not going to punch through the hill, you're just going to be in a black zone.
So I can't talk to you because you're on the other side of the hill.
And no, there's no internet and there's no mobile phones.
Obviously, this is radio.
I'm not talking about that.
So what do you do?
put a repeater on the top of the repeater on the top of that.
Yes, you do.
And then I can see the repeater and you can see the repeater.
And I talk to the repeater and it repeats what I say real simple.
In order to do that, of course, you can't do that.
There's two kinds of repeaters, simplex and duplex.
A simplex repeater is kind of like a store and forward.
So, and simplex voice repeaters are virtually unheard of.
It's pretty much a digital thing.
There have been simplex voice repeaters.
The idea is that I'll talk to on one specific frequency.
let's say it's you know 438.125 megahertz and just pick a number whatever so I talk talk talk and
it'll store up to 20 seconds or 30 seconds and then I release I un-key or release the key on
the radio, release the button, push the talk button and then it'll relay that signal and repeat it on
the same frequency for everyone else to hear but that's very problematic in all sorts of ways.
So it was definitely introduces a nice little lag into your conversation.
Oh, absolutely. But you know, in some cases it's a requirement.
You've got very limited frequencies, but honestly,
it's more of a digital thing. The idea is packet, packet, packet,
raced packet based data is ideally suited for simplex transmission.
And when you think about it you know,
there's a lot of buses out there that do this, that do a SIMP,
that do packet-based simplex transmissions.
But if you want speed and you want usability,
you go duplex.
In other words, you have an uplink and a downlink.
So on one frequency,
which is separated by a certain amount of space
from the other frequency,
so they don't interfere with each other.
So you transmit on one and you receive on the other.
So the idea is that I'll go on an uplink channel
to the repeater,
and then it'll live rebroadcast that
on a different frequency
so that everyone else can listen.
And I'll refer to that sometimes as split operation.
So the idea is that your repeater is there to help you.
But there's one problem of course with repeaters
and that is that you get one repeater
and all it takes is the person with the loudest signal
to overrun the repeater and take over.
So they can say, "Oh, I'm gonna be a jerk
and I'll just key up and play music or just be a jerk."
And yeah, this is the problem with CB radio, right?
Is that there are a lot of jerks on CB radio, turns out.
This is the thing is, this is,
I've probably prepared the least for this episode
because I can talk about this stuff
off the top of my head for hours.
And I probably would,
if given the opportunity.
So I have to rein myself in here.
So one of the really cool things
about learning about this stuff when I was younger
is I've taken a lot of this into my professional career.
So repeaters and so on,
using telemetry, simplex, duplex, data,
all that stuff over radio.
I've actually done that as part of my professional job,
but I learned about it first
when I was an amateur radio operator.
So for me, it's sort of a,
you know, it's been one of those really great dovetails
between my personal and my professional careers,
personal career, you know what I mean?
- Yep.
- Okay.
So, amateur radio.
Now, it sort of started out in the late 19th century,
but really took off in the early 20th.
And it was a result of Marconi's work.
And ham radio actually was made as an insult.
It was meant to mock radio operators
that didn't do it professionally.
'Cause of course you had professional radio operators
and they operated the telegraphs for communication.
You know, ship to shore, you know,
and telegraph operators even then
were referred under the same kind of terminology.
You know, so someone being ham-fisted or ham actor.
- That's what I thought.
- Yeah, exactly.
So ham radio is kind of like,
yeah, you're a radio operator, yeah, but you suck.
And it's like, well, gee, that's lovely, isn't it?
Good God.
Anyway, not very nice.
So I prefer, and frankly, outside of the United States,
everyone else calls it amateur radio.
They don't call it ham radio anywhere else
other than the States.
And when I was over there,
I was constantly correcting myself.
"Oh yeah, I'm an amateur radio operator" and they'd look funny.
And I'm like, "Oh, Ham Radio.
Yeah, okay, now I know what you're talking about.
All right, great."
Even though it was insulting.
Yeah, and I've known that for a long time
and I don't know why people in North America
persist in calling it Ham Radio,
because frankly, you know,
these days it's the other way around.
There are practically no professional radio operators left.
You know?
And now all you've got left in terms of radio
are the amateur radio operators.
- Yeah, well, I think that over here,
the time distance from when the terminology
first came to be ham radio,
I don't think anybody even here
associates it with ham-fisted or an insult anymore.
I think they just call it ham radio.
- Oh, sure, absolutely.
I mean, this is the problem with expressions
is that they start out with a basis and a foundation.
And then as time goes on, it becomes a colloquialism
and then the entomology of the expression is lost.
So, yeah, I don't think anyone says it as an insult.
No, I mean, it's like, oh, you're a hermeneutical operator.
No, they don't say it like that anymore.
They say it in terms of that is what it is.
So you're right, I agree.
And that's true, but the problem is knowing
the etymology of it, I kind of,
I flinch every time I hear it.
So anyway. - Yeah, sure.
- Yeah, so anyway, all right, fine, fine, fine.
So us hammies.
- Oh, that's terrible.
- We need to stick together.
So there's a bunch of organizations out there
that you may or may not have heard of.
The most common one in North America is the ARRL,
which is the American Radio Relay League,
which is a bit of a weird name,
but hey, it came from a different era.
So the ARRL.
In Australia, we have the Wireless Institute of Australia
or the WIA.
And every different country,
or a lot of different countries have their own institution
or league.
Every time I hear the word league,
I keep thinking League of Extraordinary Gentlemen,
which I thought was a really cool movie,
even though it was completely ridiculous, it was still cool.
And I remember they had this one scene
and they had to reshoot it,
it cost them millions and millions of dollars
'cause they screwed it up or something.
Anyway, whatever.
This is not defocused.
Anyhow, so all of the different frequencies
that amateur radio operators are allowed to use
are set by the International Telecommunications Union
or ITU for short.
But the representation of amateur radio operators
as a collective whole, kind of like the union, if you will,
is by the WIA and the ARRL.
And they'll petition and say,
"Oh, no, we need access to these frequencies."
Because of course, spectrum is money, you know?
And ever since the explosion of mobile devices,
you know, FM radio, television, all that, you know,
whatever, you know, but mobile phones, oh my God,
there is so much pressure.
And of course now with wifi as well, and Bluetooth,
and all these different snippets of the radio spectrum,
the pressure has never been greater to rip the frequencies away from amateur radio operators.
And to be honest, it's happening and it will continue to happen more. And why is simply
because the number of people that are actually practicing amateur radio operators is collapsing
as a hobby. It's disappearing. In 2004, there was an estimated 4 million operators, amateur
Rover Operator active around the world. In 2011, that estimate
was down to half, so down to 2 million in 2011. So in less than
a decade, it's half what it was. Now, I would expect that to be
less than a million before that much longer. Yeah, and then it's
going to be measured in the hundreds of thousands. Yeah. And
the reason I put down to this is simply the fact of, it's gone
One from being anyone can talk without wires if they're a radio operator.
They could talk overseas, they could do all that stuff.
Well guess what?
Two things happened.
One, the internet happened, and then two, mobile phones became ubiquitous.
Why on earth would I sit exams, why on earth would I pay $1,000 for a radio, build an antenna
which looks, well, debatably horrible or beautiful, depending upon your point of view.
If you're me, it's beautiful, but whatever, my wife on the other hand, anyway.
Why on earth would you go to all that trouble just to talk to your mate down the street
or across the other side of town or maybe on propagation on the other side of the world
when you can just pick up a phone and dial a number or get on Skype or whatever?
Why not?
Why would you go down?
Why would you?
Why all the trouble?
Why?
You know?
So amateur radio operators, they can say, "Hey, look, no wires."
Like I said before.
Ain't it cool?
Ain't it cool? Well yeah it's cool, but guess what?
You know, it's also expensive, it's got a high barrier of entry,
and the joy of entry is no longer all that interesting.
I can get on chat roulette.
Yep. Anybody can download Skype.
Yeah. I mean, I could call up people randomly, but I mean, you can get on chat roulette,
you can get on IRC, you can talk to whoever the heck you want,
whenever the heck you want on the internet.
What's the attraction of amateur radio anymore?
You know, I mean, if you're really into it, then that's great.
But, you know, honestly, these two things, I think, have killed it.
Or if they haven't killed it yet, I'm speaking like it's dead already.
It's not, but it's dying and its death is inevitable.
I mean, there'll always be enthusiasts.
Don't get me wrong.
There will always be enthusiasts. Yeah.
But now that I've gone and, you know, prognosticated the
the end of radio, of amateur radio, let's talk a bit more about it.
Okay, you know what a call sign is?
- Uh-huh.
- Okay, so in amateur radio, it's absolutely critical
that you have a call sign to identify who you are.
And why is because it's licensed.
So any old Joe, Bob and Fred can't jump on
and just start talking on amateur radio.
You can on CB radio, but not on amateur radio.
You need to have a, you need to be licensed
and they need to be able to, and you gotta pay fees,
at least in our country anyway,
I'm pretty sure you still do in America.
So I'll pay for five years and that would give me a call sign of my choosing, provided it was available.
Now I let my call sign lapse.
I still call myself an amateur radio operator and I am qualified to be.
And if I walked into the ACMA tomorrow, the Australian Communications and Media Authority,
I could register myself as an amateur radio operator with my certificates
and I could pay the license fee and I could get a call sign tomorrow if I wanted.
And I think my old...
So it's like a Twitter handle that you register like a domain name?
Perfect analogy, exactly.
But once someone else has got it, you're out of luck.
So anyway...
Gotcha.
So that's all lapsed, it's all gone.
Although technically I am still an amateur radio operator, I'm not an active amateur radio operator.
I've sold all my radio gear.
Basically I just, I chose.
I'm podcasting, I'm doing a website, I'm not keying up a radio.
Anyway, so call signs are typically by country, so the first two or three digits are country,
alphanumeric I should say. So for example, Australia is VK, and in North America it's
VENN, there's a few others, because North America's got one or two more, you know, amateur
Amateur Radio Press in Australia, so you couldn't just get away with the two letters.
So what I do in Australia is I split the states and they give them a number. So Queensland is four.
So I'm VK4. And then the last two or three, one, two or three digits are then basically all of the
different possibilities from there. So that's call signs. And you're supposed to announce your call
sign periodically when you're on the radio. So you might key up and say, "Hey, this is
VK4JSB and transmitting. How you doing?" And then every 10 minutes, you say, "You've got
to repeat your call sign." You say, "Yeah, this is VK4JSB. Getting back to you." It irritates
me when people say it continuously, every single time. And when you're in a conversation,
If you want to be strict about it, I guess you can, but it gets irritating, especially
if every back and forth you've got is like 10 seconds long or so.
You'll hear this sort of thing sometimes on the radio, like, "VK4JSB, this is VK4JSY.
How you doing?
Yeah, VK4JSY, this is VK4JSB.
I'm doing good.
How you doing?
Back to you, VK4JSB, VK4JSY."
Oh my God.
That would get tiring.
It's like 80% of what you just bloody said are your call signs.
I get it.
I know who you are.
Oh, crikey, whatever.
Anyway, nevermind that.
So let's move on.
Bands, modes, power, restrictions.
So amateur radio have got a whole bunch,
like I said, of frequencies and power levels
that have been permitted by the ITU,
have been fought for for years,
and they'll often refer to them by their bands,
by their wavelength.
So for example, they'll say the 80 meter band,
and that's the wavelength.
And the 80 meter band is around about 3 1/2 megahertz.
And then you've got 40 meters, which is about 7 megahertz,
and then the 20 meter band, which is 14 megahertz and so on.
And the reason we refer to it in terms of the wavelengths
is simply because that's directly related
to the size of the antennas.
So, well, at least that's my theory.
Maybe there's another reason as to why,
but I always figured that that was why.
Anyway, all right.
So I used to like working, my favorite band,
I reckon the best band in the world is a 20 meter band
because you're just above most of your atmospherics,
but you've got really great propagation.
So from an ionospheric point of view, it bends nicely.
You're only allowed to transmit certain amounts of power.
That varies from country to country.
So in Australia, we might have a hundred watt output limit,
but in America you can have one kilowatt.
It's like, oh, wow.
So there you go.
That's lots of juice, but yeah, no, a hundred watts here.
So on most frequencies.
So you restricted how much power that you can have
at the back of your radio.
Of course, you put that into an antenna
and that antenna amplifies that and you get 20 dB of gain.
well, more realistically, let's say 10 dB of gain,
you know, then obviously you're gonna have
much more peak power, and that's fine.
But certain regulations on certain frequencies
stipulate that it's the actual delivered power
at the maximum gain of the antenna.
So that kind of blows that idea out of the water,
but most of the time it's not measured.
When it comes to professional telemetry systems,
they take that very seriously.
So you can't get away with tricks like that.
Like if you've got a one watt radio
and you wanna go 27 kilometers,
you want to put in a really high gain antenna,
well guess what, you can't,
'cause the regulations state it can't be more
than this number of dB.
So you gotta be careful, but anyway, nevermind that.
All right.
- So it's not a free for all.
- It's not a free for all,
and it can't be because of interference, right?
Because if you have too much power,
you're gonna start bleeding over into other frequencies.
Other people's antennas, receivers,
are gonna be overwhelmed by the power
that you're transmitting at certain frequencies.
So there's all sorts of other different filters,
like notch filters, bandpass filters,
all this sort of stuff that goes into radio systems
in order to prevent cross interference.
Alrighty, so before we go any further,
we're gonna start talking about Q-Codes next.
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Cue codes. Do you have any idea what I'm talking about?
I do not.
Okay. Now if I were to say 10 codes, would you know what I'm talking about?
I do not.
Okay. Now if I say this, 10-4 Roger Duckwood, buddy.
Yes. Now you know what I'm talking about. Oh yeah.
10-4, Roger Dark over and under.
Okay, so in America the 10 Codes were used by the police department
and they actually came after the Q Codes.
And the Q Codes were actually developed by the British government in the late 1910s
and they're basically a way of abbreviating questions and answers
in phonetics essentially. So a phonetic alphabet of course being Alpha, Bravo,
you know Foxtrot, Gulf, Hotel India, you know you use a word that's distinctive to
represent the letter. Got it. Right so the Q codes all start with oddly the letter
Q. So you got the most four, I'm just gonna list the four most common ones. QSY
which is can be, they can be asked as a question or they can be an answer or
or they become used as nouns in a conversation,
which is a bit freaky, but there you go.
So QSY is, do you want to change to a different frequency?
- Okay.
- Or I have changed to a different frequency,
or I'm going to change to a different frequency,
or we should change to a different frequency.
So yeah, you can be used in all of those contexts.
So you would say, yeah, let's QSY 14150,
and that'll be, I'm going to change frequency,
now I'm going to move to this frequency.
or in the CB sense or the UHF sense,
you might say QSY channel 38, whatever.
Okay, QRM, radio interference, QRP is low power,
QSL is acknowledge receipt.
So those are the four most common ones
that I've come across.
Okay.
So, what are some of the different aspects
amateur radio and I've talked a bit about propagation but there's actually a
lot more to it and lots of little facets and I want to just quickly cover the big
ones mainly the ones that I was involved with. The first one I'm gonna start with
is ARDF. Now I say ARDF amateur radio direction finding and most people are
gonna say what the hell are you talking about but then I say fox hunting and
then most people know what I mean. Do you know what I mean when I say fox hunting?
I do not.
Well that's okay.
It's not like actually getting a gun and shooting a fox which is...
I assumed it was not.
No, you assumed correctly.
No, it's not. Obviously it's not that.
So no foxes were harmed in the making of this episode.
So someone builds a very low powered transmitter.
Puts a battery in it and hides it somewhere.
In the bush usually.
And then what you do is you all start from a common starting point.
Stopwatch.
And it's now your job to find the fox.
First one to find the fox wins.
They call this thing the fox.
Fox hunting.
So to do this, what they'll do is, what you have with you is,
you have to understand the basics of triangulation,
and you need a highly directional antenna,
antenna and you also need a power attenuator.
So the idea is that you'll have a radio that listens
on the frequency that the Fox is transmitting on.
Usually the Fox will transmit just a series of Morse code,
you know, da, da, da, da, da, da, da, da, da, da, whatever.
And it'll be on a continuous repeat on that frequency.
You gotta listen for that.
And you'll have a handheld antenna and you sort of sweep it
around to find the highest frequent, highest,
most directional, the most,
best direction for the signal.
And then you've got to run across to another area
to take another reading,
and to try and triangulate where exactly it's coming from
and its distance.
And then as you're getting closer,
essentially you have to increase the amount of attenuation,
otherwise it'll overload your receiver.
So those components go together,
you know, compasses, maps, and whatever.
This is all before GPS.
So to help you locate the fox.
And there's competitions worldwide about,
with ARDF, it's still a big thing.
So I went on a fox hunt in Clearview.
Was very lucky that one of the guys was big into it
and competed internationally, I never did.
But there's an amateur radio weekend.
In North America, they'd call it a ham fest.
And anyway, so we just call it the Clearview weekend.
We had two, where I grew up in Rockhampton,
there was one at Clearview,
which is most of the way to Mackay,
North of Rockhampton, there's another one out West at Fairburn Dam.
These come up once a year and there's this little mini ham fest where amateur operators
will get together and do amateur radio-y things, compare gear, buy and sell stuff.
It's a bit of fun, actually.
The auction's the best part.
I did a fox hunt.
Some guy was very nice enough to lend me his gear.
So I had a couple of rounds of fox hunting and I participated in a round and successfully
sprained my ankle.
Because trying to run through bushland chasing a fox is, ow, it's more hazardous than you
might think.
Yeah.
Because you're like, "I've got to get to the fox, god damn it!"
Oh crap, it has tripped over again.
And of course when you trip over you don't want to break this $100 antenna, right?
So you're going to take the beating, not the antenna.
And you fall over and you get stabbed by the antenna and you're like "Oh my god"
Yeah, it's...
I'm picturing a bunch of nerdy guys that don't normally see much outdoor time
All strapped down with expensive gear all over their person
Yeah, yeah, that pretty well sums it up, holding this ungangly antenna in front of them with a funny pistol grip on it
Yeah
It is bizarre
But anyway, it's also kinda cool
Anyway, alright
Well I say it's cool. Anyway therefore it's cool. Possibly not. All right so
moving on. We'll talk about propagation. So there are these things called DX
competitions. DX being short for distance transmission.
Or what's just referred to as DX. Okay so when you're chasing skip, you're chasing
isopheric propagation, you're chasing DX. That's the one of the
lingo, slangs that they'll use.
Anyway, so they'll have DX competitions
where you essentially, there's a timer.
It'll start at say 12 midnight on one date,
finish, I don't know, 8 a.m. the next day or whatever.
24 hour, 48 hours contest.
And you have to contact as many other people
doing the contest at that time.
And there'll be a minimum distance.
So you can't contact a local and call that a contact.
they have to be greater than a few hundred miles away,
otherwise they don't count.
In other words, it has to be actual propagation.
You can't just have a competition and talk to locals.
I'm sure those competitions existed,
but that would not be a DX competition, would it?
Anyway, so I participated in one of those.
It was the Jack Files contest,
and yeah, I made 102 contacts,
and I came 78th in Australia.
So yeah, pretty piss poor showing really.
But never mind that, that's okay, it's the only one I ever went in.
And uh...
I only made two contacts on Morse.
Uh... the rest of them, and I made another two because you get bonus points for Morse
and um...
if you uh... do on Lull Friedge as well. So I made a couple of contacts on 160m band as well.
Uh... which is also hard because you need an enormous antenna.
And it's also difficult because you can only do it at night time.
Anyway, right, moving on.
So that's DX competitions.
What's also an adjunct to that is the DXCC.
And that's sometimes referred to as the Century Club
or the Worked 100 Countries Award.
And the idea behind that is that over a period of time,
if you have confirmed contacts with other people
in a hundred different countries around the world,
then you are eligible for the DXCC,
which is something that not too many people have.
And frankly, you know, maybe it's not a big thing anymore,
but so I can get on the phone and dial a hundred countries
in a hell of a lot less time than it would take me to do that.
But a friend of mine around the corner from me,
literally around the corner from me,
had the DXCC certificate.
So he was, he'd done really, really well.
Clive, a friend of mine.
And anyway, great bloke too, by the way,
helped me out a lot early days.
Actually was the local WIA representative
who witnessed/administered my entry exams.
So it was a very, very cool guy.
Anyway, so that's DXCC for those people
that just can't get enough DX.
And for people that are even more hardcore than that,
they have these things called DXpeditions.
So that's where you go to an island or territory
and you set up your radio gear
and you contact as many people as possible.
And so for example, VK0,
Macquarie Island is one example.
So it's a tiny little patch of island, and I mean tiny.
You literally camp on, set up your antennas,
bunch of solar panels, batteries, and so on and so forth,
and you just, you know, contact people.
Now, I have never been on a DXpedition.
I've never attempted DXCC.
I did one DX competition.
Some would say I lacked commitment.
As far as I'm concerned, I was sane.
All the other people,
(laughs)
totally crazy.
But anyway, you know what?
Hey, go for it guys.
All right, moving on.
Packet radio.
Packet radio is exactly what it sounds like.
Packets of data transmitted over the radio.
What else can I say?
So I had a old 9600 board TNC,
terminal node controller,
connected up to an old XT,
an 8086, 8088, sorry it was an 8088.
Oh God, that was a while ago.
Anyway, I picked it up cheap.
It wasn't new.
It was secondhand when I bought it,
but it was dirt cheap.
I got it for like 25 bucks.
Perfect for running packet.
It would sit off in the back corner
and you would go,
"Hum, der, der, der, der, der, der, der."
Insert data noise impersonation there.
Anyway, and it would tick off in the background
and you could send and receive data and emails
and there was a DigiPeter and all that stuff,
Simplex DigiPeter and all that stuff.
And again, that was all happening,
that started happening just before the internet took off.
But then when the internet took off, it killed packet
because of course packet radio and radio frequencies,
if I've got an FM channel that's only 25 kilohertz wide,
I'm not gonna get much more than 9,600 board.
And you know, I'm 19,200, maybe, maybe, I doubt it.
You're gonna start bleeding across into the adjacent
channels because you need more bandwidth to have more data.
You know, Shannon's theorem, which I skipped,
but anyway, Shannon had a theorem.
Point is, packet radio was simply too slow
and it just died.
And I mean, it's still around, but you know,
honestly it's, yeah.
So an interesting hybrid recently with the internet though
is the IRLP, and that's the Internet Radio Linking Project
where you take repeaters and using tone calling,
you can literally dial up and say,
I want to connect this repeater with another repeater
on the other side of the world.
And the internet becomes the bearer and connects the two.
So rather like duplex operation locally,
when the two repeaters are linked,
you'll start getting transmissions and receptions
from the other side of the world, potentially,
if they're linked together.
- That's really cool.
- It is very cool.
So you can go in, you can go to the repeater
with the right equipment and in that connection,
you can just go dial up.
I wanna talk to in Calgary, which I did do
just for the heck of it once.
and I dialed in on 2 meter band and I was talking over 2 meter band to a repeater
which then went into the internet, sprung out and Calgary came back out talking into a VE6.
Which, you know, is cool.
But let's be honest, is that...
Why don't we just, like, do Skype?
So, again I refer you back to why Amateur Radio is dying.
Still, it's a thing, and it's cool, and there you go.
Okay, QSL cards.
So it's basically just a radio on the last mile.
Exactly, yes, that's exactly what it is.
Okay.
And it's honestly just...
They did it because they could.
Yeah.
Yeah. Anyway, alright.
Well, they're radio guys.
Well, exactly. Yeah.
Anyway, okay, so QSL cards.
QSL, QSL, which I said earlier, QSL is Acknowledged Receipt.
So what the heck's a QSL card?
QSL card is kind of like a postcard,
but it's a physical acknowledgement that I talked to you.
So let's say you and I talking on radio
and I'm saying, "Hey Vic, this is VK for JSP
"speaking to Vic, NN1, whatever, whatever.
"How you doing today?"
- 10-4 good buddy.
- 10-4, no, you, that's CB lingo, man.
You're in amateur radio now.
We don't use the 10 codes here, you know?
Anyway, the point is, and I actually got yelled at once
for letting slip a 10 code, 'cause I came from CB radio.
So yeah, anyway.
Okay.
So what'll happen is at the end of that contact,
you may choose to send me a QSL card.
So we will exchange physical mailing addresses over the air.
(laughs)
Other option of course,
is that you can register in a QSL database.
So if you don't like putting that stuff over the air.
And a QSL database is essentially a service
where I sign up, you sign up,
and you can say, right, I want this to get to such and such.
You send off to an address in a country
and it'll be forwarded on to that particular individual
for a fee.
Or you can simply opt to,
they can get your physical address and mail stuff to you.
So anyway, the point is that QSL cards are sort of proof.
And I used to collect QSL cards
and I've got a couple from the States
and it's kind of cool.
And most of them from different parts of Australia.
And I even print off my own QSL cards
back when I was in CB radio.
And when CB radio, my call sign that I made up for myself,
'cause in CB radio, you can make up
whatever call sign you want,
was 23S150, which is, you know,
latitude and longitude of Rockhampton, essentially.
That was creative, I guess.
Anyway, yeah, so I print off my own QSL cards
and send them out to people that I made contact with.
And it's kind of a nice thing.
So I acknowledge receipt, here have a QSL card.
Anyway, all right, moving on.
One of the other things in amateur radio is QRP,
which is low power.
And the challenge in QRP is to use
the minimum amount of power possible.
QRP is usually defined as one watt of output power
at the radio or less,
and with low power to make contacts over the same distance.
Someone said any idiot can put a kilowatt shoe box
on the back of your rig and blast it out to the States.
Of course, that was not me talking.
But the point is anyone can do that.
I say anyone, anyone with money.
But the perception is that it takes what skill, talent,
I don't know, whoever, to operate in QRP
and make the same contact.
So making sure you have the lowest loss coaxial cable,
the highest efficiency antenna
with the highest gain possible,
knowing exactly when the skip is going to come in, come out,
the best polarization to use,
all of the best frequencies to work on,
all of that stuff all goes into being able
to make contacts on low power where others would fail.
So QRP operations is one of those things.
And you put that together, for example, with DXCC.
So some people have got QRP, DXCC certificates.
So you work a hundred countries on low power.
Anyway, I was never into QRP,
although I did build a transceiver once, sort of.
And I'll get to that in a minute.
Okay, two more things to talk about,
and then we'll talk about my projects and then we're done.
So Oscar.
Now I don't mean Oscar the Grouch.
I mean, oddly, yeah.
Orbiting, and I don't mean some kind of an award
that people win for, Oscars are acting, right?
- Yeah. - So that's how much
I pay attention to that.
Okay, Oscar, orbiting satellite carrying amateur radio.
That's what it stands for.
So since the late 50s, early 60s,
we've been launching satellites
and some of them have carried amateur radio gear.
Some of them have been entirely funded
by the amateur radio community
for amateur radio operators to use.
And some of the packet repeaters and so on and so forth
have actually been satellites.
So there have been times where I didn't personally,
but a friend of mine in Rockhampton had satellite tracker
with an elevation azimuth rotator
and using some computer software,
he was able to calculate and track
onto some of the low earth orbit satellites.
And essentially you have a global bulletin board
and this was before the internet, right?
I mean, actually I'm trying to think back
if this was before the internet when I first saw it,
it wasn't, but it was available as a technology
before the internet and before computer software,
you know, you did the tracking yourself.
So there'd be tracking plots and, you know,
times of day and earth location,
you could figure out, you know, what location.
So every minute or two,
you would tweak the antenna position azimuth and elevation
based on a set of numbers in a table.
And that would track the satellite for you
to get maximum signal.
And that was while it was doing a pass, right?
Does it pass over low earth orbit
is like 90 minute earth orbit typically.
So that's the same sort of height as a space station.
And you'll get, you know, like a,
depending on the elevation above the horizon,
you'll have anywhere from a minute to 15 minutes
of time to upload what you need to upload.
and then of course, and after our--
- Before your window closes.
- That's right.
Once the window closes, and of course you're out of luck.
You know, if your upload didn't finish in that time,
you're screwed.
And then of course, people on the other side of the world
can download whatever you uploaded.
So it's kind of like an orbiting,
an orbiting BBS in a sense.
Very, very cool stuff.
Anyway, didn't get into that myself.
Really wish I could have though,
but just the bar was too high in terms of expense.
Another one, I started swimming the space station.
That was another dream of mine, never happened, alas.
Anyway, moon bounce is the last one I'm gonna talk about.
Jeez, I love moon bounce.
And I love moon bounce because it's just such a cool idea.
Now, imagine just for a second
that the moon was a really good reflector.
It isn't, but just imagine that it was.
And it was a big mirror.
Well, if you pointed a big enough antenna off of the moon,
then you could actually bounce your radio signal
off the moon and back to the earth again.
And you'd be able to get reliable,
round-the-clock communication to another part of the planet.
So they call this EME, Earth, Moon, Earth,
but moon bounce just sounds so much more cool.
So let's just go with moon bounce.
So I'm bouncing signals off the moon, baby.
Oh yeah.
And in order to do that, in order to do that,
you need an enormous amount of power.
You need enormous array of antennas.
And some of these moon bounce antenna arrays
have got something like 24 Yagis all phased together
through a collinear phasing array.
And they're transmitting like one kilowatt of power
through that.
And to receive it on the other end,
it's a similar setup just to receive it.
So, yikes.
I don't know what the path loss is, but it's enormous.
And the tracking has to be precise
because you're transmitting over such a large distance,
you need to make sure the antenna
is perfectly aligned with the moon.
Yikes.
And that's why when I did the signals
to and from the moon, that's why they had this massive radio telescope in parks in New South Wales
that brought the signals back. Have you ever seen a movie called The Dish? It's an Australian movie but
still very cool. I enjoyed it and it's a bit, you know, a bit dicky in parts but generally it's very good.
About the story of, you know, the radio telescope in parks in New South Wales, which I've been to,
oh yeah, and how it used to, how it picked up the signals from the television signals, signals from
the moon and relayed them around the world when first steps on the moon.
So that's why they need a big parabolic dish because you know hey it's hard to pick up
those signals it's a long way away.
Again another facet of amateur radio I never really got into, moon bounce.
So my projects, now I've built so many antennas it's not funny but I tell you what a friend
A friend of mine, Sean, is an avid FM broadcast radio listener.
And there's another effect I didn't talk about.
It's not ionospheric propagation.
It's something called ducting.
So what you get is an effect at certain frequencies
between about 50 megahertz and about 700, 800 megahertz,
where you're going to get what they call trophospheric ducting.
It's caused by a temperature inversion layer.
And the idea is that because of an inversion in temperatures,
that temperature inversion and turbulence
it's created causes the radio signals to bend at a higher frequency than normal.
So rather than punching out to the ionosphere and then punching out into
space, they bend back enough and they ricochet down this little duct, hence
they call it ducting, the tropospheric duct, the barrier between the
two temperature layers in the atmosphere. And those ducts often open up all
over the place. Usually they'll open up between places that, you know, there's no
one living so you don't know about it. But when they open up between places
is that there are lots of FM radio signals,
for example, you'll sometimes hear.
So for example, in Brisbane,
we would have, there was like B105 and triple M
radio stations and you could pick them up in Rockhampton
if the tropospheric ducting was in.
Now to pick those up better,
you could buy generic FM radio log periodic
from Dick Smith Electronics or Radio Shack, wherever.
But unfortunately, they were designed for 88 to 108 megahertz
which is the FM broadcast band.
and unfortunately their gain therefore is not as high.
So Sean asked, 'cause he knew that I was into antennas,
if I could design him an antenna
that would give him the highest amount of gain
in the sweet spot, which was between,
it was a one megahertz range, not a Yagi,
but a log periodic, a high gain log periodic
for a much narrower frequency band.
So that to date has been my favorite antenna
that I've designed and built for the FM broadcast band,
specifically to pick up the two favorite radio stations
of his from Brisbane from Rockhampton,
which is about 600 kilometers away,
which is about 400 miles away.
So that remains my favorite antenna,
despite the fact that after a while,
a big fat bird stood on it and snapped some of the elements,
but nevermind that.
Next, the version two of John's log periodic
for FM broadcast would have had much thicker insulators.
I'm just saying stronger ones,
'cause it's not just about,
it's about physical strength as well as gain,
which I learned the hard way
as I one day showed up at his place and saw one of my elements was sagging down to the
side and been snapped.
That was a sad day.
Anyhow, alright.
Bummer.
Alright, next.
I built so many wire antennas it ain't funny, but one of them that I did build out of recovered
wire from a...
Oh dear.
Picked up some surplus transformer wire, which is essentially just coated copper wire, so
coating or clear lacquer they use it for winding on transformers. Anyway so I
picked some of that up cheap and as you do and anyway I turned it into a wire
Yagi. So most Yagis are made out of physical like tubes of aluminium because
it's much stronger but I made one out of wire. Because I didn't I couldn't
afford the... Just because. I couldn't afford it I couldn't afford to build. You
know I was a kid I was like you know 16, 15, 16 years old I didn't have money to
to build or expertise.
Later on, I got better at it.
FM Broadcast Yagi I built when I was what, 19, I think,
something like that.
You know, the Yagi was when I was still, you know,
mid teenager and yeah, it worked okay.
Fixed direction, of course,
'cause it was strung up in the trees and so on,
but anyway, it worked sort of.
Hey, anyway, I'd like to say my,
sorry, I'll talk about my long wire then.
I did an inverted L long wire once
And in order to match that, I pulled an old capacitor,
an air capacitor out of an old TV set, valve TV set.
And the worst part of it was that being young and stupid
at the time, didn't realize that RF energy
is kind of dangerous if you're not careful.
And this particular thing here on the front of the TV,
it had a Bakerlite knob, which would,
had a shaft that connected into the actual shaft
of the capacitor.
So as you change the channel on the television,
it would change the capacitance,
that would change the frequency,
that would change the TV channel.
That was the way it used to be done in the good old days.
Here's the problem, right?
Is that I'd taken that BakerLite connector off,
so it was now exposed.
The whole thing was a one conductive piece of metal
with two sets of insulated plates,
like sets of fingers that go in and out of each other.
- Uh-huh.
- So I had keyed this thing up
because of course you can't measure reflected power
without putting power into the antenna.
So I was measuring and tuning it to try and get the standing wave ratio of the antenna
down to tune down to an acceptable level that I wasn't going to blow up the final transistors
on my radio.
So what did I do?
Reached out with my right hand to tune it.
And that's at the moment where the RF energy jumped across the webbing in my right hand
and blew a chunk out of my hand.
Wasn't huge, but ow, ow, yeah, that hurt a lot.
So that's when I discovered the tried and true way.
My patented method after that was to get a wooden clothes peg and put that on the thing
so that it didn't blow a hole in my webbing.
Anyway, never mind that.
Like I said, I learned things the hard way.
Okay, finally, I'd like to call it my crowning achievement, but let's be honest, it only
half worked.
So it's my crowning half achievement in amateur radio was I built my own transceiver.
The design was the very popular design by a radio amateur called NN1G, well that's his
call sign anyway, and everyone called it the NN1G transceiver.
Designed for 20 meter band, the receiver mostly worked, it didn't tune across the entire range,
it was a dual conversion Super Hetrodine I believe from memory, and the transmitter though,
it needed a couple of toroids, and the problem with the toroids was that I had to get the
specific toroids with specific characteristics and the design called for ordering from DigiKey
and at the time I couldn't get DigiKey stuff because that was in the States and I was not
and they didn't order overseas so I was stuck and I tried some different toroids that I could
source locally in Australia. Turns out they were not exactly the right characteristics so the
transmitter portion never worked. But I etched the circuit boards, I soldered all myself, bought all
all the components, assemble it myself.
The receiver mostly worked, the transmitter never worked,
but still that was my crowning achievement
in terms of physical hardware.
However, my future in software was somewhat a little bit
sort of foretold at one point
because I had an Icom IC706 radio
and I built a very simple TTL converter
to plug into the DB9 port, serial port
on my computer at the time,
which is a 8386, whatever the hell.
Anyway, and so I'm plugging this thing in
and it'd be great if I could talk to the radio
and use some software to set frequencies.
It's had a hundred memories.
So what I did is I wrote some software.
It was based in DOS, it was written in Borland.
See?
- Yeah.
- And it used a rolling bar menu,
so two-dimensional rolling bar menu.
So, you know, all done through the keyboard,
but also had mouse support.
And I used direct interrupts.
I didn't use any of the libraries
I just like doing things the hard way. Anyway, and yeah, it won second prize in the home brew
competition and that was in 90... I forget, 97, 98, I forget, something like that anyway.
So it's pretty cool. Yeah, it was pretty cool actually and most of the home brew entrants in
the amateur radio competition locally were of course, you know, hardware like amplifiers,
low noise amplifiers, you know, and transceivers that worked. I don't like mine. And, you know,
but mine was different. Mine was software and no one had entered software before. So I honestly
think it won second prize more out of novelty than anything else, rather than being any good.
I never sold it as a product, although I probably should have. But within a year or so of mine
winning that prize, someone had released a Windows version, which was, let's face it, a heck of a lot
more user-friendly. So yeah, mine kind of never really saw the light of day. I don't even have
screenshots of it anymore. I have the original source code somewhere, I think. But anyway,
I should put it up as a yeah, as a yeah, this was useful once, Hall of Fame or something, I don't know.
Anyway, and honestly, that's it. I could talk more, I could talk a lot more and honestly, I'm not going
to because, well, let's face it, I don't know how many people care. But here you go, there you go.
Someone had asked for me to do an episode about my background with amateur radio and radio in
general, so there you go, now you know. And hopefully some of that's been interesting,
but honestly, bottom line is that as a hobby it is dying, and whilst it set me on the path that
it did into electrical engineering and further on into control system engineering, which is what I'm
I'm doing now, the internet is so much easier in so many ways,
mobile phones, so much easier in so many ways.
And frankly, writing software for that stuff is just as cool
and pushes a lot of those sorts of buttons
that Amateur Radio used to push for me.
So I still feel like I'm not missing out in that respect.
- Yeah.
- So, yeah, so that's it.
And I see we have a couple of questions
for the Q&A session that'll be happening after the show.
So stick around after the music, after you hear the music.
if you've listened to the podcast offline
and you'll hear that.
So stick around for the Q&A.
So yeah, anyway, if you'd like to talk more about this,
you can reach me on Twitter @johnchidjee,
that's J-O-H-N-C-H-I-D-G-E-Y,
and check out my writing at techdistortion.com.
If you'd like to send any feedback,
please use the feedback form on the website,
and that's where you'll also find show notes
for the episode on the podcast's "Pragmatic."
You can also follow "Pragmatic Show" on Twitter
to see show announcements,
like when we're going live, for example,
and any other related materials that might crop up.
I'd like to thank my co-host, Vic Hudson,
for joining me once again.
And Vic, what's the best way for people
to get in touch with you?
- They can follow me or find me on Twitter @vichudson1.
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And that's it.
Thanks for listening, everyone.
And thanks again, Vic.
- Yep, no problem.
(upbeat music)
[Music]
(air whooshing)
(bell ringing)
So let's go through the Q&A, Q&A, Q&A, what do we got here?
Okay, so Russ, you're asking about,
so Russ Newcomer in the chat room asks,
"Can you talk about antenna sizes and signal reception?
"As in, if you have a bigger antenna,
"is reception necessarily better?"
Answer is yes, bigger is better
because you're capturing more RF energy.
And there's the theorem, the reciprocal theorem
of antennas such that if I design an antenna
to have maximal gain in transmission,
it will have maximal reception as well.
So let's say, one of the things I didn't talk about
was beam width.
The beam width is the angle from the center point
of your antenna to the two points,
the two 3 dB power points on your plot.
So you're plotting the maximum amount of gain
around your antenna and the maximum gain
is in the forward direction usually is the front of the lobe,
but as you move to the left and the right of that lobe,
eventually the power will drop off
to three dB less than the maximum.
They call that your half power points,
so your three dB points.
That angle is your beam width.
So when you quote an angle's beam width,
it'll be, let's say it's, I don't know, 25 degrees.
So there's 25 degrees of, basically,
so that's what, 12 and a half degrees each side of center,
where you're gonna get approximately maximum gain.
So the idea is that, yes, the bigger the antenna you go,
the better your signal reception is going to be.
Hence, things like Arecibo.
However, one of the things I didn't talk about,
didn't even think about talking about it until just now,
is the other idea,
which is creating a virtually big antenna through phasing.
Now, phased arrays do this.
And I did, I guess, talk about this
when I talked about moon bounce,
but the idea is that you'll get,
let's say you'll get 20 antennas
and each of them will feed in
through what I call a phasing harness.
And the idea of a phasing harness
is that each of the connections from each of the antennas
is exactly perfectly the same length.
All of the antennas are exactly perfectly the same,
matched exactly perfectly the same.
And they all come into a common feed point
such that all of the signals coalesce
and they essentially, they're all in phase.
So with signals that are in phase, of course,
they're additive, they amplify.
So you get more signal reception.
So, but the phasing harnesses
have to be very precisely made.
Everything has to be all very well calculated
that to work. Anyway so phasing harnesses and all that it's all really cool stuff
and the macro scale of this is if you look at radio telescopes there's one
the funny the first one is the very long base array in New Mexico and there's a
whole bunch of these are spread up all around the world now they're becoming
quite very popular on radio astronomy is that each of those
antennas essentially is a smaller parabolic dish but you've got lots of
them and they'll spread out in the X and Y direction and the idea is that you can
and then add all of the signals together
to essentially create a similar capture area
to an enormous virtual radio antenna.
So that's the same idea.
And you can move the different antennas
along a bunch of railroad tracks
to position them to change the size of the antenna.
So larger area, different gain characteristics,
depending upon what you're trying to listen to.
Most phased arrays are fixed, however, not adjustable,
but in radio astronomy,
you're gonna go to that sort of trouble.
make them adjustable. There'll be a few that aren't, but you know most of them should be mobile.
Follow-up question, Russ asks, "Phasing harnesses are not a home option, right?" Well sure, why not?
Absolutely you can. I mean the laws of physics are the laws of physics. You want to, you know,
phase a couple of antennas together, none stopping you. In fact, I have seen some people that live in
bad TV signal reception areas do that. So I've seen multiple Yagis, and you'll see them stacked
horizontally and vertically.
And so you'll see like two or three or four antennas
either in a configuration.
So I've seen houses that have got four Yagi's,
well, they're log Yagi's,
for TV antennas that have gone through a phasing harness
into the house just to pick up,
'cause they're in a fringe area.
And if you wanna pick up TV, that's your option.
So it's much less common these days, of course,
with cable television and in Australia,
You know, like, you know, Foxtel and whatever.
So you got satellite TV.
And as long as you've got a view of the sky,
you've got satellite TV, right?
So, you know, shrug.
But anyway, it's not, it's not a question,
it's more of a statement, but yeah,
amateur radio is treated like public access television
in the US, yes, yeah, it is a bit.
- Yeah, it is.
- Yeah.
So a lot of people take, turn their nose up at it,
but you know, in the zombie apocalypse,
(laughing)
you want the radio guy around.
(laughing)
I build an antenna for my HDTV out of old clothes hangers.
Absolutely, why not?
It works better than the antenna that I bought from the store.
That's the thing is that television antennas are funny beasts because a rabbit ears television
antenna is so heavily loaded.
When I say antenna loading, what I'm talking about is that you'll load up with an inductor
and a capacitor or inductors and capacitors depending on the match.
that does is it reduces the physical length of the antenna needs to be
because well you're quote-unquote you're loading it right so the idea is that
electrically it appears longer than it really physically is and that's great
for shrinking antennas and making them tiny it's terrible for efficiency so if
you want to have an efficient antenna rabbit ears are not your friend
Rabiteers are only useful in high signal reception areas.
So if you're out in the sticks, you need an external antenna, free from your house, free
from the walls, free from the roof, for high gain in order to get performance.
That's just reality.
So what's in these new, I'm sure you guys got them there too, if you go to the store
you see now they sell digital TV antennas and it basically just looks like a little
UFO disc.
Okay, so what that's got in it is what's referred to as a loaner.
Is it just a coil of wire?
It is, but it's loaded and it's got a low noise amplifier in it and sometimes it has
an active matching circuit.
So the idea is that some of them will detect the frequency specifically that you're on
and they'll tune themselves to that frequency so that you get the best possible efficiency
at the frequency you're trying to tune into.
Other ones, far more commonly, are simply a low noise amplifier.
So the idea is that they will take the raw signal and they will amplify it before it
goes into the coaxial cable into your TV set or your radio.
The downside of that would be it's going to amplify noise and all right?
That's right.
But the low noise amplifiers, you know, hence the name suggests, LNAs are designed...
LNAs are very common in microwave transmission.
And the reason is that you want to boost this, you want to give the signal a kick before
it goes into your coax.
you're going to lose power in your coax.
So far better to amplify it
before it goes into the transmission line
where it's going to pick up noise and lose power than after.
Because all a radio receiver is,
or a TV receiver is, is an amplifier.
It amplifies the received signal to a level
which it can strip off the data and then display it,
you know, or present it in audible form,
like through a speaker.
So ultimately, ultimately it's all about the sensitivity.
And if you have a good low noise amplifier,
at the end as close as possible to the antenna,
then you're gonna improve your chances of picking up
the weakest possible signal,
which is why in radio telescopes,
they will have the lowest low noise amplifiers you can get,
which is usually cooled by liquid nitrogen,
because what you wanna do is you wanna reduce
the amount of molecular movement in the actual receiver
in the low noise amplifier.
Because if you reduce that amount of power,
you end up with the cleanest possible, sorry,
if you reduce the temperature,
reduced molecular movement that reduces the Gaussian noise that you'll get in the amplifier.
Obviously that's all so ridiculously over the top it ain't funny,
um, unless you want to have a really really really low noise amplifier with a bunch of liquid
nitrogen you've got to keep topping up. Which I never did and I don't think anyone would ever do.
Well maybe there'd be some nutters that would do it. I mean I say nutters, I mean survivalists.
And I mean, and if you were a survivalist with a low noise amplifier with liquid nitrogen,
how the hell are you going to make your liquid nitrogen once the world goes to crap?
I mean, you're just not, are ya?
I mean, how are you going to do that?
You're going to have your home nitrogen factory?
Of course you're not.
Eh, whatever.
I think you've got to figure this out, John.
We're counting on you for the zombie apocalypse.
I sold my radio gear.
Were you listening?
God.
I'm not licensed anymore.
I'm a has- I'm a has- I don't think that'll matter at that point.
No, it won't matter at that point.
I'm a has-been.
I'm a radio has-been.
No.
(upbeat music)