Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by KG5ILR, Sep 22, 2019.
Has anybody considered using a raspberry pi and a sdr dongle for a transcever combination.
I don't see why not, except possibly needing to limit the sampled bandwidth. The new Pi4 is relatively beefy, I'd try it with the 4GB RAM model, and make sure to use the USB3 ports. If you try, please let us know!
Seems like it could be a possibility one of the pins has an rf output but I would imagine that a pretty good band pass filter would be needed. I will post what I figure out.
The WiFi external antenna connection is the only RF connection, Normally used when mounted in a metal case.
I have a RPi3 that I use a SDR V3 with. It works fair, But the RPi3 has a lot of RF signals across the HF spectrum.
PiTx allows for Tx'ing on one of the GPIO pins. Square wave, so you pretty much have to have some sort of filter to prevent harmonics. Really low power, too.
I've had good success using the TARP Hat and Direwolf with an RPi for HF Tx.
One major issue with LF/VLF could be power out on the Tx side. You'll probably need a PA if you want to be heard. VLF antennas are also problematic.
Assuming you're using an average short Marconi, which most do for LF (2200m), you'll see efficiencies at about .0005%. At VLF, say 30kHz, you'd see about .000002%
My 400W TOP with a Hafler P3000 equates to about 200mW EIRP (before the load coil & variometer) into a short Marconi (40' vert w/ 100' hat) for 137 kHz.
It's a tough nut - but it can be cracked. In any event, good luck !
Jim, WQ2H / WK2XAH