Re: [Discuss-gnuradio] Car alarms and garage door openers

[Rick Parrish]

Michael Milner wrote:

> I just took a look at my car's keyfob with the USRP RFX400 board (it seems
> to transmit around 433.923MHz.  It is using FSK modulation, a few tens of
> kilohertz deviation.  It demodulates pretty well, but the centre frequency
> isn't very stable (Is there any way to automatically detect the centre
> frequency within a range?)
>  
Might be one of these ...

http://pdfserv.maxim-ic.com/en/an/AN3765.pdf

The older SAW filter designs would "wiggle" the TX frequency to 
compensate for any slight mismatch between the TX and RX filters.

-rick