Re: [Discuss-gnuradio] AR5000 and downconversion

[Henrique Miranda]

Hello Alan,     

>I've recently found that I have access to several standard radio
>receivers,
>including an AOR AR5000 and AR8600. Naturally, these both have a 10.7MHz
>output IF and thus aren't much use in combination with my 20MSPS A/D card

Take a look at a sampling technique called "undersampling" or "harmonic
sampling".

It is perfectly possible to sample a 10.7 MHz IF signal at a rate of
2 Msps, for instance, as long as:

 * the analog bandwidth of your ADC is higher than the IF frequency
   (easily met by your A/D card)

 * the IF signal bandwidth is fully contained in a Nyquist region

In this example the maximum allowed bandwidth would be 600 kHz
(10.7MHz +- 300 kHz)

Nowadays many digital/software radio systems operate this way.

You can find a more detailed discussion on this subject in Frerking's
"Digital Signal Processing in Communication Systems" book.

Cheers,   

Henrique