Saturday, July 07, 2018

FM DX With the SDRPlay RSP1A, or: My Debut As an FM DX-er

Admittedly, I'm a MW DX-er, and have done very little FM DX in my 47 years as a DX-er. However, when I got my RSP1A with up to 10 MHz sampling rate in late 2017, I decided that I wanted to test its FM capabilities this summer. I had already noticed that it seemed to be quite sensitive on the FM band.

I set up a three-element FM antenna in the attic in my DX HQ in Kongsfjord, pointing south. Now, FM DX is a lot more common on lower latitudes than my 71 degrees north, so to be fair I didn't have hope of receiving much. I monitored the FM band to and from every day from mid-May, but I had forgot to check when FM-DX ace Ole Forr messaged me on the evening of June 25.

When I connected to Kongsfjord via Teamviewer, it was the start of an E-skip stint which would evolve into a super evening!

I had set the RSP1A to 8 MHz sampling because 10 MHz seemed to be to much for the software or hardware to handle. Still, 8 MHz covers quite a bit of the FM band. I used SDR Console to record the IQ stream into an 8 TB hard drive, and changed centre frequencies so I could cover the entire band at one time or another. It soon emerged that every 100 kHz had at least one signal, many had three or four.

At one point, the combined signal levels were so high, I had to throttle back a bit on the RSP1A's gain to avoid overloading.

After reviewing the recordings, I ended up with a log of 200 FM stations. Most of them ID'd by RDS, a few by announcements since the RDS wouldn't lock.  13 countries were logged: Russia, Belarus, Finland, Estonia, Latvia, Lithuania, Poland, Sweden, Norway, Denmark, Netherlands, United Kingdom and Faroe Islands. Denmark, Sweden, Poland and Lithuania dominated the log. Stations from 908 til 2411 km away were heard, and the lowest powered were 100 watts. The FMLIST map below shows all stations logged. I did hear two unidentified German stations, and one with an Austrian accent, so more countries were there.

The RSP1A performed very well. Of course, I don't know how it would compare to a dedicated FM tuner, but on the face of it, it seems to be a very capable FM receiver.  And no dedicated FM tuner will ever listen to an 8 (or 10) MHz of spectrum at one go! SDR Console also worked well, and RDS data with the all-important PI code showed up with little delay, even for signals not in the clear.
FM e-skip from Arctic Norway on June 25, 2018.


Roger G3XBM said...

Sounds like you hit a sporadic E opening.

Radio Club Berrouaghia CSP said...

What software name do you use, Map program ?
73 de Kamel , Algeria DXer
FB: Ghalem arsalan

Tim Bucknall said...

at that price i'm seriously considering getting one.

if anyone reading this has compared it to airspy HF+, how does sensitivity at 88-108mhz compare?

the HF+ is pretty hot
my qth is south cheshire uk. using the HF+ i can see the carriers of RTL from northern france on 87.7 (St omer 1kw 407km) & 87.6 (2 possible txs both sub 1kw) during advert breaks

Tim Bucknall said...

PS: i'd have put the notch filters at 380-400mhz (UK tetra system for emergency services)
800- 8xx (4G)
+ various mobile phone base station bands