Re: [Discuss-gnuradio] Tx/Rx in the 144 MHz (2m) band

[Johnathan Corgan]

Lee Patton wrote:

> I want to transmit and receive in the 144 MHz (2m) band, but there isn't
> a daughterboard available for that band.  144 MHz will alias to 16 MHz
> with a 64 MHz sampling frequency.  So, sub-nyquist sampling will work on
> receive.  However, I'm not sure how to achieve 144 MHz on transmit.  (By
> the way, I need to be coherent between transmit and recieve.) Any advice
> on the simplest course of action?

The output of the DAC is a stair-step waveform that is rich in harmonic
content.  Normally these harmonics are removed by a low-pass
reconstruction filter.  The BasicTX card does not have one, however,
which allows you to transmit at 16 MHz, then bandpass filter
(externally) the 9th harmonic to get 144 MHz.  Your output power will be
much lower, of course, than the fundamental.

-- 
Johnathan Corgan
Corgan Enterprises LLC
http://corganenterprises.com