[CQ] Cheap SDRs?

[AF6MQ]

most Software Defined Radios send the I and Q signals to the L,R  
channels
of a sound card.  basically, you tap into the radios IF stage,
downconvert to match audio frequency that sound card can "hear",
then run software that FFT/RDS/etc on those signals.
works fine in reverse too as long as your sound card has
a decent bit-resolution.  thats pretty much how the Soft66
all the way up to the FlexRadio do it.

plenty of free software to do IQ, and even more commercial stuff
with direction finding, noice hum removal algos, etc.

this could be done with any radio that has a discrete IF stage.

if you can find a simple FM transistor radio that will tune the band  
you want,
you might be able to find an IF stage and tap it.
work your way backwards from the audio amp circuit with an oscilloscope.


heres the geek on IQ,
http://www.sdrforum.org/pages/sdr05/2.2%20Comm%20Theory%202/2.2-01% 
20harris%20et%20al.pdf

and heres a guy who did it himself,
http://www.g0ehv.btinternet.co.uk/SDR.htm

--gaspo.


>> You can have very cheap narrow-band DSP by using a sound card and the
>> output of an SSB receiver with the filters switched out. And you can


>
> Sounds very interesting. Can you point at any links so I can learn  
> more?
>
>
> -- 
> Michael Shiloh
> KA6RCQ
> www.teachmetomake.com
> teachmetomake.wordpress.com
> _______________________________________________
> CQ mailing list
> CQ at lists.noisebridge.net
> https://www.noisebridge.net/mailman/listinfo/cq