ARLA/CLUSTER: Episódio 194 da série "Foundations of Amateur Radio" - Mais aventuras com o WSPR

[João Costa > CT1FBF]

Foundations of Amateur Radio #194


*More WSPR adventures*
Previously I've spoken about the joy of making something out of not much.
On that theme I've covered WSPR, the Weak Signal Propagation Reporter, a
mechanism to use a modest station to report signals received, which is
something any suitably interested person can participate in, no license
required.

For a time I had my radio, a Yaesu FT-857D connected to a Windows XP
notebook running WSJT-X, a piece of software that has the ability to set
the frequency of your radio and then listen to what the radio is hearing,
attempt to decode it and then report on what was heard.

The beauty of this system is that you're using your own station to report
signals heard, that is, your own antenna, your own coax, your own radio.
Essentially you can use it to see what can be heard from around the world
at your station.

I had this running for a while, but the set-up was less than satisfactory,
because I use the same radio and antenna to run weekly nets, the computer
was running Windows XP and running out of disk space since WSJT-X has the
option to save all the audio heard, which was clogging up my drive.

It also meant that I was required to remember that I needed to reset the
volume of the radio, set the squelch just so, disconnect and more
importantly reconnect the antenna when there were storms about and a few
other annoyances that became just a little too much for it to be fun.

After doing this for a couple of months I just gave up and put it into the
too-hard basket.

The other day I started afresh.

I started with a Raspberry Pi. It's a single board computer, about the size
of a credit card, that comes in at about $30, is powered off a USB adaptor
and runs Linux. Since I've been using Linux for around 20 years now, it
seemed like a natural fit. I managed to obtain an RTL-SDR dongle which if
you're not familiar, is essentially a USB device that you can use to listen
to RF frequencies. Without going too deep, these gadgets started life as
USB DVB-T and FM receivers, you know the USB dongles that you can plug into
your computer to watch free-to-air TV or listen to FM radio.

Back in March of 2010 Eric Fry got curious about figuring out if he could
make a Linux version for one of the dongles work by reverse engineering the
communication between the dongle and the supplied Windows software. In 2012
Antti Palosaari built on that and published his findings on the linux-media
mailing list. Things exploded from there.

So, an RTL-SDR dongle, connected to a Raspberry Pi, running Linux.

At this point it would be great if I could report success and show and tell
everything I've learnt, but then for that to happen I would need to
actually have had success and I'm not quite there yet.

I managed to decode one, count 'em, one, WSPR packet on 6m, once.

Of course I couldn't help myself and started to improve things and since
then I've not heard anything.

I can tell you that there is plenty of documentation online about the
subject, and I'll be adding my version of that once I've got mine up and
running.

There's a few things to work on, for example, listening on 6m is all fine
and well, as long as there are 6m stations within hearing that are on and
transmitting. Turns out that the station that I heard once last weekend has
been switched off for a week. I've just changed bands, to see if that
improves things, but only time will tell. I have also been using a
mechanism to change bands automatically every 15 minutes, but without any
spots I'm not sure if my set-up is working or not and I've just been
unlucky not to hear anything.

The challenges continue, but then I suppose that's why I'm here in the
first place. I will add that a problem shared is a problem halved. I
mentioned my challenge to a local amateur who sprang into action and set-up
a WSPR beacon, just so I can test against it. I'll let you know how I go,
or you can monitor for my spots on the WSPR website and celebrate when you
see a spot with my callsign on it, because I will be, celebrating that is.

As an aside, it continues to surprise me that this hobby has its fingers in
so many different pies and my chosen profession of IT Geek is just another
aspect of amateur radio.

I'm *Onno VK6FLAB*
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