As far as I know only 2 operational satellites currently have downlinks below 30MHz. RS-15 has a beacon at 29.352MHz and AO-7 has one at 29.502MHz.

My "Simple-Too" interferometer has a DDS (Direct Digital Synthesiser) based local oscillator. The frequency for the DDS output frequency can be set using software on a PC, and so it is possible to set the observing frequency very accurately. When "YASI" was up and running out at Mick's place I would sometimes disconnect YASI and plug Simple-Too in so I could listen to the satellites. I like satellites :-)

The RS-15 beacon turns on and off intermittently as you can hear in this .WAV file I recorded. AO-7 is a battler but she's a pretty busted up old bird and only sometimes turns on when it comes out of eclipse, and comes up in random modes each time. Some orbits I couldn't hear it and others it sounded great. Here is a .WAV of some CW telemetry I recorded during one good pass, I assume the regular fading is due to the fact that my antennas respond to only one polarisation but the satellite is constantly spinning.

The graph below shows a pass of RS-15 as seen by the Simple-Too interferometer. You can see the effects of the beacon turning on and off in the auto-correlation data in the top panel. The bottom panel shows a clear fringe pattern as the satellite moves through the interferometers beam, where some positions give a positive cross-correlation and others a negative. I think this is an extremely geeky thing to do, I'm very proud of it :-)