Radio adventures
2021-Jan-24I bought myself an RTL-SDR
I had great fun building simple radios as a kid, I even had a CB radio. I didn't set it up again after we moved house. I didn't use them all throughout my late teens or either of my degrees. Eventually, I left them in the UK when I moved out to Canada.
Enter RTL-SDR
I bought an RTL-SDR, a cheap Software Defined Radio (SDR) receiver. I also got a set of three cheap antennas (not an affiliate link.) Total cost was 90.05 CDN, including tax and shipping.
My RTL-SDR
I found that I can use it with my phone and my main laptop. Huzzah!
Inside this little USB device is a Realtek RTL2832U which is officially for receiving and decoding Digital Audio Broadcasting (DAB, a digital radio standard) transmissions. It just sends the samples directly to the host, which then decodes them as it needs. This means that the host can ask for one of many frequencies and decode it as something other than DAB, like amateur radio, aircraft transponders, and so on.
Getting it working on Android
This was very easy. I did need a USB-A to USB-C adaptor, but no other equipment aside from that. I used SDR Drive and RF Analyzer, which just worked.
RF Analyzer on my Pixel.
Getting it working on Fedora
This was a little trickier than the phone, but not by much. I use gqrx for decoding the signal, and I needed to make sure the dvb_usb_rtl28xxu module was not loaded, otherwise it might interfere with gqrx.
sudo dnf install gqrx rtl-sdr sudo rmmod dvb_usb_rtl28xxu
That was mostly it. After that, I started gqrx and chose my device, the Realtek RTL2832U, and hit the "play" button in the top left-hand corner. Sorted.
Long wave reception
I set the device string to rtl=0,direct_samp=3 to get anything lower than about 26MHz. This was fine, but took a lot of messing around since most places suggest direct_samp=2, and don't mention that it's a comma-separated list. Ah well!
What I found
Commercial radio
I found a couple of local radio stations easily, notably CBC Radio 1 and CBC Music. They're analogue FM stations. CBC Music is actually clearer through my SDR than through my actual radio. Granted, the aerial is bigger, but I was still impressed.
CBC Music, 92.1 MHz
I also found Virgin Radio Victoria broadcasting in my local area. It's the only HDRadio station I found. You can tell by the little "steps" on the side of the spectrum. This lets a HDRadio-compatible radio receiver play the high-quality digital audio if it is good enough, or fall-back to analogue once it is not good enough. There's also enough bandwidth here to add other stations in there too!
Virgin Radio Victoria, 107.3 MHz
Maybe one day I'll see what's in those digital side-bands. I am pretty sure at least one of them will be Virgin Radio Victoria, but maybe there's a whole extra station hiding in there?
Public service radio
I can faintly pick up Weatherradio Canada on 162.475 MHz. If I recall, this was the first non-commercial station I found. It's Canada's NOAA-equivalent, giving continual weather reports through with a synthesised voice.
Canada Weatheradio, 162.475 MHz
I also found the Victoria Harbour Automated Terminal Information System. I think this is for the airport at the harbour, but I'm not sure. It seems to do weather reports for the local area.
Victoria Harbour Automated Terminal Information System, 120.0 MHz
Oddly, this doesn't sound like a synthesised voice to me. It could be that they record each a weather report as it arrives, then just loop it.
Weird stuff
I did find a few strange things. The first was Coast to Coast AM. They claim to deal with "UFOs, strange occurrences, life after death, and other unexplained (and often inexplicable) phenomena." As a Brit, I'd never heard of such a wacky station, but there it was, plain as day. I think I found it at 1075 AM?
There is this strange signal at 458.465 MHz. It looks like CW (Morse) at first glance, but it does not sound like it. It sounds like a semi-regular chirping noise. It runs for about 20 - 30 seconds, then repeats a minute later or so.
What is it?!
Finally, there is something on 462.9 MHz. It continuously alternates between a high and a low frequency, which sounds like a cardiac ultrasound with beeps instead of "woosh." Occasionally it changes to a less consistent pattern before returning to the "heartbeat."
Sounds like a heartbeat. I'd say it's aliens if I worked for Coast to Coast AM.
What didn't work
I couldn't pick up the local amateur net, known as Aurora Net. I tried both 7.1 MHz and 6.6 MHz, but I was either at the wrong time, or my equipment isn't sensitive enough.
Similarly, I couldn't pick up any CB transmissions. I suspect that they aren't widely used, so I don't know if it's my equipment or not. I might get a cheap CB radio to test the theory.
Although the Realtek RTL2832U is designed for DAB and Digital Video Broadcasting (DVB-T), it does not work in Canada. It would theoretically work, but Canada has HDRadio for digital audio and the "Advanced Television Systems Committee (ATSC) standard for digital video. I can decode HDRadio, but I haven't tried yet. ATSC needs about double the bandwidth this device supports, so I can't decode that.
Future plans
I'd like to try to receive some air traffic control signals. I'm fairly close to both YYJ and YWH, so I expect that I could get some if I took my equipment outside. I'm near to Summit Park, which has good elevation. Not sure if I want to brave the cold, the pandemic, and the suspicious glances of the dog-walkers though...
Similarly, I'd like to see if I can get some marine radio communications. I think it should be possible, but I'll need to be much closer to the water.
Since I'm relatively near a harbour, I should be able to get some ship locations from the Automatic Identification System. I'll need some decoder software and to take a walk to the harbour's edge I suppose. Maybe I could track BC Ferries or the Victoria Clipper coming in to dock.
There's the old stand-by of tracking aircraft using their Automatic Dependent Surveillance -- Broadcast (ADS-B) beacons. As with boats' AIS, I'd need some extra software to decode it. Once decoded, I can plot them on a map.
Finally, as I mentioned, I might buy a CB radio to test out my equipment. I'd use it to see if I'm listening on the right frequency. Then I'd take a walk to see if I can be heard from different locations, like the peak of Summit Park.