Re: [Discuss-gnuradio] external clock issue with B100 + WBX

[Marcus D. Leech]

> Hi,
> I am using the same clock reference to both b100 devices.
> the clock reference is XL microwave model 500, it is rubidium based, 
> and it has multiple outputs.
> since I am connecting it to both B100s (the actual same clock 
> reference) I was expecting that the Rx and Tx frequencies will be 
> exactly the same. but I still got 570Hz difference.
> when I did not invoke the tune request command, the Rx was distorted 
> (the Tx was fine, I tested it with a spectrum analyzer)
>
> Regards, Guy
Define "exactly the same".   Even a Rb reference oscillator has some 
imprecision in it, although not usually as high as 600ppb, unless the vapour
  tube is nearing the end of its life.

How did you measure the frequency offset?  The measuring device has to 
have a precision much better than the thing you're trying to measure,
  or your results will just be nonsense.

If you don't use offset tuning (using tune_request with an LO offset), 
then the DC anomaly will be right in the center of your passband.  If 
you're using
  a narrowband carrier for testing, that DC offset will interfere with 
your measurements.




--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org