USRP N210 10MHz reference input

GNU Radio
1

Greetings, first post so please be gentle…

I have managed to build the UHD driver and gnuradio
(v3.3.1git-380-ged78ba5d) etc under Ubuntu 10.04. Running from the
gnuradio-companion it all works exactly as expected ie I can demodulate
broadcast FM OK and device streams reliably up to sample rates of 20Msps
fine.

I’m trying to get my shiny N210 to accept a 10MHz reference and 1PPS
(from a
Trimble Mini-Thunderbolt GPSDO).
The problem is this: the ‘Ref Clock’ switch in the ‘UHD Single USRP
Source’
doesn’t appear to function. Switching it to External does seem to do
anything. The GRC code is the same no matter whether I set the ref clock
to
int or ext (I checked the python code with diff).

The 1PPS input seems to be working OK - tested ‘test_pps_input’ from
UHD -
passes with GPS connected and fails when I remove the 1PPS. The 10MHz
input
is the right level ~10dBm. I’m guessing this is a software problem and
not a
hardware one (this is a software radio right? :slight_smile: )

Anyone got any ideas? Thanks in advance,

Rob.

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2

The problem is this: the ‘Ref Clock’ switch in the ‘UHD Single USRP Source’
doesn’t appear to function. Switching it to External does seem to do
anything. The GRC code is the same no matter whether I set the ref clock to
int or ext (I checked the python code with diff).

Works for me, here is my diff when i switch the ref to External and
click generate:

  self.uhd_single_usrp_source_0.set_gain(0, 0)

-Josh

3

Thanks Josh - knowing what to look for helped - as does my using the
right
file =) Just confirmed operation by gently phase modulating my reference
clock from a signal generator with a CW RF input - the sample phases
follow
as they should.
R.

Josh B.-3 wrote:

Works for me, here is my diff when i switch the ref to External and

  self.uhd_single_usrp_source_0.set_samp_rate(samp_rate)

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