Hi Marcus,
No, I haven't fooled with LO level adjustments.  I set the LO at about 3
dBm and did not change it.  The LO freq is indeed 2x (LO at 4884MHz with
center freq at 2442MHz).  I suspect that my custom software, which was
developed for first B210 and then X310 with several daughterboard variants,
may be sending tune commands in a way that is not ideal for an external LO
configuration.  There was a similar issue when I first started using TwinRx
with "companion" or "external" LO and UHD would issue warnings about tuning
one channel first and then the other when both channels had to be at the
same freq because they shared an LO.  So, my request for examples was to
help me see if I am issuing the tuning requests correctly for this external
LO config.


On Fri, Apr 6, 2018 at 7:32 PM, Marcus D. Leech via USRP-users <
usrp-users@lists.ettus.com> wrote:

> On 04/06/2018 05:14 PM, Rob Kossler via USRP-users wrote:
>> Hi,
>> Are there any examples for using the N310 with external LO?  I have
>> gotten some strange results (strange spectral mirror-ing) when using as
>> just a 4 channel receiver.  I am using the "args" argument to set
>> rx_lo_source, but my code is setting the individual channel frequencies as
>> I do for other USRPs and I noticed various warnings in the terminal window
>> for each channel that I tune.
>> On a separate note, I get some strange results if I set the clock_source
>> to external in the args (using with OctoClock). If I leave it internal, no
>> problem. For now, I am leaving it internal until I can solve the problem
>> above with LO source.
>> Rob
>> Rob, just shooting from the hip here, since I haven't "lived" with an
> N310 yet...
> Have you tried adjusting the LO levels let's say 2dB in either direction
> to see if that changes the imaging behavior?  Also, remember that the
> external LO input
>   on the N310 must be a 2XLO -- at twice the desired Fc, and only up to
> 8GHz (giving a 4GHz antenna frequency).
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