Web SDR and the Partial Solar Eclipse

Last Friday (20/3/2015), the UK experienced a deep partial eclipse, reaching about 92% over north Wales.

Steve Nichols, G0KYA, who is the RSGB's main propagation man, tried to raise interest by getting as many people as possible to monitor AM radio stations by ear, and with recordings where possible.

I was unable to monitor my ham station or an AM broadcast radio because I was hurtling ahead of an advancing weather front to keep seeing the eclipse with a telescope that I can assemble and disassemble faster than a special forces soldier deals with a gun!

The Moon covers ~92% of the Sun, as seen from southern Anglesey, Wales, 20/3/15. Image (C) this blog.

So, a few days in advance, I'd looked into the possibility of monitoring an AM station in Iceland (RÚV) via a web-based SDR.  These are really very good facilities, which very usefully permit audio recordings to be made and downloaded.  I wasn't sure if my internet connection, or the overall connection to the web-SDR would stay up reliably during the 2.5 hours of interest, or that the recording would allow such a long file.

So, at about 08:01UT, I set the recording running at the University of Twente's SDR in the Netherlands.  The only other suitable web-SDR station in the UK suffered from horrendous and continuous broadband QRM, making it essentially unusable.

Path of the eclipse, totality path in deep pink (timeanddate.com)

After returning home and stopping the recording at 10:29UT, by which time it was actually raining outside, I found that the web-SDR monitoring had worked perfectly, generating a 120MB file.  You can find the recording here.  If you want to refer to my time indications, you will have to donwload the file and play it on software that shows this (like Windows' native player.)

I think I'm right to say that, at 1h23m into the recording (about 09:24UT), RÚV's signals start getting stronger.  By 1h35m in (about 09:36UT), the signal is very strong and clear, just like at night time.  By 1h54m in (about 09:55UT), the station is well on its way to daytime noise and weak signals again. This seems to tie-in nicely with the progression of the eclipse.

RUV 1 signal strength over 2h28m, showing a clear increase, peak and then decrease in strength as totality came to pass between transmitter and receiver. Don't be fooled by the higher bars in the first hour or so; most of this is noise.

So, I think that is a successful demonstration of the effects of an eclipse on long wave radio propagation.  It's also a successful demonstration of how, if the web-SDR location is in the right place relative to the eclipse, it can be a very useful way to allow mass-participation in radio propagation experiments during eclipses.

If you have any way to objectively analyse the recording and yield a plot of signal strength output with time, that would be very interesting to receive.  Until then, I have to rely on my ears!