Re: [Discuss-gnuradio] Using external clock with USRP2/WBX

[Eric Schneider]

On Sun, 2010-06-13 at 08:12 -0700, Damien S. wrote:
> Hi all,
> I'm trying to use the external clock input of the usrp2 with WBX in receive
> mode. Unfortunately after processing the recorded signal there is still a
> clock drift despite the fact i'm using a GPS reference clock. So i suppose
> that i'm making something wrong.

Can you specify how much offset you see?

I presume that the transmitter is also using a precision timebase?

> 1) I'm using a square 10 Mhz reference from a GPS receiver (Novatel OEM4)
> which has a 300 mV peak-to-peak amplitude -> this amplitude is sufficient ?

I'm not familiar with that unit, but 300mV should work.

I've used a Trimble Thunderbolt and a Jackson Labs Fury GPSDO without
issue.
 
> 2) I activated the external clock by selecting the external SMA option in
> the usrp2_source block in GRC. Could somebody confirm that is method works ?

Yes, it works.  I just tested the GRC source and sinks with a signal
generator and my USRP2 definitely tracks the "External SMA" clock.

--Eric