XPost: aus.radio.amateur.misc, rec.radio.amateur.equipment, rec.radio.info

Foundations of Amateur Radio

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Much Ado About ...

Posted: 16 Jul 2022 09:00 AM PDT http://podcasts.itmaze.com.au/foundations/20220717.foundations-of-amateur-radio.txt

Foundations of Amateur Radio


There are days that my brain just cannot keep up with all the ideas that I
have spinning around and today is one such experience. Before I take you on this wild ride I will mention that I'm only going to focus on the amateur
radio specific things going on, but I tend to have a couple of projects on
the go at any one time, much like a messy desk piled high with paper,
books, gadgets, parts and coffee cups, my mind has this sometimes
exhausting tendency to see connections between various projects and often
this results in deeper rabbit holes, so with that in mind, I'd like to make
an attempt at describing all the amateur things that are going on at this
very moment.


So, here goes, hang on!


It all started with two friends, independently and until now, unbeknownst
to each other, playing with a mode called Digital Radio Mondiale, or DRM.
It's something I've talked about before. One friend is trying to decode it,
the other is trying to generate it. I'm sitting on the side cheering on
because I think that there will come a time when I understand enough of my PlutoSDR that I can create any form of any mode and not be limited to the
SSB bandwidth that current technologies use and be able to receive and
generate say a 20 kHz DRM signal.


In order to advance my learning, I started the day wanting to describe a PlutoSDR project. I wanted to spend some enjoyable time playing, making
some progress and then telling you about it. I did play, I did have fun, I
did make progress, but trying to explain precisely what and how was where I came unstuck.


I began describing the difference between analogue and digital radios and
how there's a fundamental difference in how a signal comes to exist in
both. That quickly turned into a conversation about I/Q signals, a
discussion that I've been putting off for a while because I'm still not
happy with my own understanding of it, let alone any attempt to explain it
to you in a coherent and hopefully fun way.


The complexity of explanation was brought home to me during the week when
NASA Administrator Bill Nelson used an example to explain an image taken by
the James Webb Space Telescope.


The phrase he used was this:


"if you held a grain of sand on the tip of your finger at arm's length,
that is the part of the universe that you're seeing"


That seemed pretty clear to me. I could imagine a grain of sand on my fingertip, extending my arm and grasping the idea that hidden behind it was
a small slice of the sky representing how big the image was. For me that explanation was excellent, especially when Bill Nelson went on to say that
the things you were seeing were galaxies, each made of a hundred billion
stars, each likely with planets in orbit.


Only I discovered that the explanation using a grain of sand wasn't
universal. I was surprised to learn that for some it got muddled up with
the grains of sand in the universe and the relationship between those and
the one on your finger.


To be clear, I'm not saying that there is anything wrong with
misunderstanding, but it reminded me in a visceral way that how we explain things matters and there are plenty of times when my own efforts fail to achieve their intended purpose, of making things easier to understand.


Given the importance of I/Q signals within the whole conversation on
software defined radios, I don't want to do a half baked attempt and fail.
I will say this, an I/Q signal is a way of precisely representing a radio signal, but only to stop you thinking about it further.


I was talking about how my mind accumulates things.


The NanoVNA that's sitting on my desk, gifted to me by a friend, is a
fantastic example of the similarity between it, software defined radio and
say a TinySA which I came across last week. Let me unpack that a little.


A NanoVNA is a piece of testing equipment, as is a TinySA. They test
different things. Both have the ability to generate and measure a signal
and in that they share the abilities of an amateur radio transceiver that
can also generate and receive a signal.


That right there is a very deep rabbit hole, so I'm going to purposefully
step away and continue the journey of observation, only pausing to mention
that my PlutoSDR has all the same capabilities and in that it's not alone.


The fundamental difference between these three devices is software. There
are a few other things, but on the whole, software.


So, I'm carrying around this mush of things that are almost the same, but different, almost understood, but not quite, almost ready to explain, but
not yet.


In an attempt at going forwards by moving sideways, I went on to
investigate other things, prompted by people who send me emails. For
example, code plugs and DMR and frankly I felt unclean reading the various explanations. I'm a firm believer in Open Source and this is like asking an Icom owner to explain the benefits of using Yaesu hardware.


Another question was around bending antennas, as-in, what happens when you drive down the road and your VHF antenna bends, or what happens if your HF dipole is bent to fit in your garden. Superficially I can say that the
antenna changes as its bounding box changes shape. That means that the feed point impedance will change, as will the resonant frequency. The radiation pattern will also be affected, but sitting down and discovering just by how much is going to take more time than I have available whilst attempting to string together some coherent words on a topic I love.


So, in an attempt at telling you what's going on in my world of amateur
radio, I leave you with this question:


"What was I talking about again?"


Now I remember, this is about just how complex, fluid and interesting
amateur radio is for me and in that observation lies why I'm here doing
what I do.


"What makes you keep coming back for more?"


I'm Onno VK6FLAB
This posting includes a media file: http://podcasts.itmaze.com.au/foundations/20220717.foundations-of-amateur-radio.mp3

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