Electronics > RF, Microwave, Ham Radio

Use two cheap digital (optical) USB sound cards for diversity reception?


Please excuse me if this is a bit speculative..

I recently bought a "Syba" "SD-AUD20101" for around $10, and for the money, despite my disappointment that it doesn't sample at 192 KHz as its vendor claimed, its still quite a good value.  (Ive seen other similar USB dongle sound cards, for as little as $2- but I doubt if they have as good sound quality and include an optical output)

So these cheap USB sound dongles, which use a Via vt6230 chip, even have direct digital out, they have a SPDIF optical output in the form of a red LED that sends digital data through an optical cable, sharing the output miniplug, which also is useful I would think because it lets you get a precise timing, that you can't get with USB. (musicians always bitch about the lack of precise timing with cheap sound cards, better clocks are one of the reasons pro level sound cards are more expensive)-

I don't know if it would matter so much to most people that they had an optical out but it might make a substantial enough difference for SDR, because the SN is better and no ground loops, which I suspect would be a big thing in the soundcard sdr context..   Also, perhaps, timing, both pairs could not just share the same crystal, their outputs could also be interleaved..  again, not so knowledgeable about this, just speculating..-

The RTLSDR (running two or three dongles from one crystal) has been used for passive radar, because the locked timebase allows comparing (two receivers and) direct and reflected signal's timing relationships.

If the dongles use a crystal, (lets just assume that they do have a crystal, I don't know that for a fact..) anyway, you likely get the rest already..

See here for the inspiration   http://kaira.sgo.fi/2013/09/passive-radar-with-16-dual-coherent.html   (also http://kaira.sgo.fi/2013/09/16-dual-channel-coherent-digital.html )

Suppose you make two side by side receivers, sharing the same local oscillator, of course since they will be tuned to the same center frequency. But two antenna inputs, as well as two separate sets of i and q output, digitally connected to the computer sound cards as well, via the low noise high dynamic range, synchronized timing optical outs.

 Would that offer an advantage over a single receiver - making it more useful for long distance reception under severe fading or be useful data for getting rid of - canceling out noise?

Might be worth trying it out, given their low cost.


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