SDRs have been a game changer for radio hobbyists, but for ham radio applications, they often need a little help. That’s especially true of SDR dongles, which don’t have a lot of selectivity in the HF bands. But they’re so darn cheap and fun to play with, what’s a ham to do?
[VK3YE] has an answer, in the form of this homebrew software-defined radio (SDR) helper. It’s got a few features that make using a dongle like the RTL-SDR on the HF bands a little easier and a bit more pleasant. Construction is dead simple and based on what was in the junk bin and includes a potentiometer for attenuating stronger signals, a high-pass filter to tamp down stronger medium-wave broadcast stations, and a series-tuned LC circuit for each of the HF bands to provide some needed selectivity. Everything is wired together ugly-style in a metal enclosure, with a little jiggering needed to isolate the variable capacitor from ground.
The last two-thirds of the video below shows the helper in use on everything from the 11-meter (CB) band down to the AM bands. This would be a great addition to any ham’s SDR toolkit.
SDRs which don’t use RTL2832U and can go above 1.7GHz are still expensive.
Why do you exclude the RTL2832U for above 1.7GHz?
I know almost nothing about SDRs but they interest me greatly. Awhile back I looked into the cheap dongles at about $30-$60 and the HackRF One at over $300. I couldn’t really understand why the dongles were so much cheaper other than the frequencies covered.
It seems like all the cheap dongles use the RTL2832. Is there a downside to that chipset that I am unaware of?
I would like to be able to decode medium wave, Canadian and USA. AM band the stations that broadcast in analog CQUAM AM stereo, there’s still are a couple dozen of them, and the audio is just fantastic, but I would like to be able to have an SDR that can decode CQUAM using the Phase-modulated L-R signal. Anyone that can contact me on this? Thanks, 73
Back in the 2000s, we built SDRs with the help of sound cards and the line-in port.
We built a direct conversion (DC) receiver and used the 7 to 12 KHz wide IF for decoding/demodulating the signal.
Or we tapped 455 KHz IF of an existing radio, but this involved a bit more work.
With a stereo line-in, the use of i/q signals was possible.
Have a look at SDRadio or Dream software, both a classics!
https://www.i2phd.org/sdradio/index.html
https://sourceforge.net/projects/drm/
But please note that the codec for DRM wasn’t/isn’t free.
It might be necessary to get a custom EXE of Dream with built-in DRM codec.
PS: For SAQ reception, an antenna at the sound card’s line-in can be used, even!
Building a little VLF receiver is more efficient, though.
Here’s more information (not affiliated): https://www.prinz.nl/SAQ.html
Great info ! Thanks.