Re: [Discuss-gnuradio] FM Radio USB Dongles?

[Johnathan Corgan]

On Fri, 2006-11-10 at 18:44 -0500, michael taylor wrote:

> The bigger limitation, in terms of flexibility, is "Worldwide FM band
> support (76–108 MHz)" from their Features page of the Si470x single
> chip FM receiver. I don't see the interest, it is a FM-only receiver
> basically with the broadcast band (worldwide).

Well, it's been interesting enough for people to be selling $50 FM Radio
dongles by the bucketful :-)

>  The 96Ksps over USB is
> irrelevant given the "IF" (output from the Si470x) signal is being
> (lowpass) filtered at 23 KHz. 

But since the original audio was only 15 KHz, you could lowpass filter
at the 96 Ksps rate and then decimate by three, increasing the effective
dynamic range above 10 bits.  But see below...

> You could add it to gnuradio, but it
> would be for novelty's sake only, as you cannot make use of GNU
> Radio's DSP features other than just with the audio output.

That's the real limitation, to be sure.  In fact, the USB controller
shows up as a Windows sound card, so you could use these with the
existing audio drivers and some fiddling for control.  As the original
poster wondered, it would be far more useful to get downconverted I/Q
out of the thing.  This would be great, for example, if someone ever
gets around to implementing an IBOC decoder for HD Radio.


-- 
Johnathan Corgan, AE6HO
Corgan Enterprises LLC
address@hidden