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

[Lee Patton]

On Fri, 2007-06-22 at 10:32 -0700, Johnathan Corgan wrote:
> 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.

Thanks, Johnathan! That is a really interesting idea.  I'll look into
it.

-Lee