Re: [Discuss-gnuradio] An interesting application for my new USRP... some input requested

[n4hy]

There are no other clock sources of error in your analysis system since 
the clocking is all driven by
the 64 Mhz stabilized oscillator.  No sound card oscillators are 
involved.  This will be a straight
digital transfer to the analysis program(s) and all clocks from one 
reference.

I would  do this as follows:  Insert a known tamed oscillator in LSB and 
have the measured
tone in USB and use "arithmetic" to back out the offset (phase and 
frequency) using the known
source.  Since this is a frequency measuring test,  a little phase 
modulation makes little difference.
Using the USRP or SDR-1000, etc.  the known reference is the key and you 
are doing that.
In the SDR-1000 case, using the tamed and controlled 8640B,  put it in 
LSB,  the signal of
interesting in the USB (say) and use the console to record an IQ 
signal.  The analysis and the computation
is then easy.  The digitally recorded signal is resampled based on the 
reference signal.  Then the
frequency of the unknown signal is computed using a large FFT and the 
known new sample rate.  You
could do it this way with a known external reference and a combiner and 
a digital recording program.
You record the known reference and the unknown signal in the same 
passband.  Again, I would
use my tamed 8640B as the reference.  Then you can do it with analog 
receiver and a digital
recorder.

Bob

John Ackermann N8UR wrote:

> Hi Bob --
>
> Yup, using a 64MHz Reflock II is exactly what I was planning to do. 
> It'll be driven by one of the house Cs or Rb standards that's compared 
> against GPS.
>
> One of my questions -- whether a frequency-stabilized 64MHz clock 
> would remove all sources of frequency error, or whether there was 
> other clocking going on that could affect frequency measurement 
> results. Sounds like you're saying there isn't.
>
> John