ARLA/CLUSTER: Episódio 137 da série "Foundations of Amateur Radio" discute o "Virtual Radio"

[João Costa > CT1FBF]

Foundations of Amateur Radio - Episode 137

Virtual Radio

There is a feeling of anticipation in the air, the year has started,
there are so many different ideas bubbling through my mind that I feel
like an excited puppy dog wagging its tail.

I've been playing with a wonderful piece of software called GNU Radio,
more on that in a moment.

So, I have for a while been dissatisfied with the offerings of SDR
software. There is lots of development going on, lots of new toys
being invented and many different hives of activity in this area.

It's not unlike the progression from reel-to-reel based radio
broadcasting via VHS tape, to computers with audio files. There are
lots of solutions solving specific problems, but there are also a
group of solutions looking for a problem and only time will sift out
which one is worth the effort.

In amateur radio we deal with valves, resistors, capacitors,
inductors, transistors, integrated circuits, crystals, connectors,
solder and many, many different physical things.

I'm a computer guy, have been since I was in primary school. I grok
computers, more-so than any aspect of anything else. Amateur radio was
intended as an escape from this world, but initially to my dismay, but
now to my delight, computers are making serious inroads into the
hobby. Not just as peripherals that take care of logging, messaging,
propagation forecasting and the like, but as integral parts of the
radio.

I looked at GNU Radio several years ago and wasn't able to understand
what it did and how it worked. I didn't have enough in the way of
radio skills or vocabulary to get started, but in learning about my
hobby I now have a much better understanding.

GNU Radio is a tool, a piece of open source software, that allows you
to build circuits inside a computer that process information. Not
unlike how filters, amplifiers and oscillators do this inside a
physical radio.

If you want to change the behaviour of a radio, you need to alter a
circuit by changing components, or re-design the circuit entirely and
re-build it. Hours of planning, soldering, testing and the like, just
on a hunch or an idea. It's how we've been doing development for
centuries.

GNU Radio allows you to tweak a radio on the spot, in real-time, and
see what it does. The feedback loop is immediate. You build up a
sequence of blocks, an oscillator, a filter, a combiner, splitter,
decoder, spectrogram, waterfall, whatever and if you need it do do
something else, you either swap out one of the blocks, or change one
or more parameters, better still, replace a fixed parameter with a
slider so you can change it while it's running to see what happens.

For example, displaying a Lissajous figure in the real world involves
two signal generators, cables, an oscilloscope, power, gain settings,
timing, several hundred, if not thousand dollars worth of gear. In GNU
Radio it involves two signal source blocks and an oscilloscope block,
joined together. All there, three blocks, two lines and it's working.

Making an FM receiver in GNU Radio involves a source of radio
frequency information, say a $20 RTL-TV dongle and an FM decoder
block. You can display it on a waterfall with a third block, or listen
to it with an audio block.

To make matters even more interesting, you can build your own blocks,
transmit if your radio is capable and test all of this without ever
needing to go to the local electronics store or heat up a soldering
iron.

I have no doubt that this changes amateur radio for me and I'm fairly
sure it will do the same for you.

I'm Onno VK6FLAB



To listen to the podcast, visit the website:
http://podcasts.itmaze.com.au/foundations/ and scroll to the bottom
for the latest episode. You can also use your podcast tool of choice
and search for my callsign, VK6FLAB, or you can read the book, look
for my callsign on your local Amazon store, or visit my author page:
http://amazon.com/author/owh

If you'd like to participate in discussion about the podcast or about
amateur radio, you can visit the Facebook group:
https://www.facebook.com/groups/foundations.itmaze

Feel free to get in touch directly via email: onno  itmaze.com.au, or
follow on twitter: @vk6flab (http://twitter.com/vk6flab/)

If you'd like to join the weekly net for new and returning amateurs,
check out the details at http://ftroop.vk6.net.