I’m sure this has been previously discussed on the list, but I can’t
find the discussion in the archives…
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?
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.
On Fri, 2007-06-22 at 10:32 -0700, Johnathan C. wrote:
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.