On 09/26/2018 02:24 PM, Arun kumar Verma wrote:
Hi Marcus
well I am connecting external ref of 10MHz on Ref Input SMA connector
and once I connect this and set my clock source for external source
then we are getting spurios, these spurs are low but for AM,FM audio
demodulation even Hz suprs can create probelem and that is what we
are facing. Right now what we using a VCXO of 50ppb satbility and
what we noticed that with the internal clock there was a shift in
frequency of about 5KHz at 3GHz input while with external Ref shift
was around 300Hz. Is it possible to switch off supply manually for
internal oscillator and board still works?
Regards,
Arun Verma
Could you please post an image of the situation, showing the spur levels?
------------------------------------------------------------------------
*From:* Marcus D. Leech via USRP-users <usrp-users@lists.ettus.com>
*To:* usrp-users@lists.ettus.com
*Sent:* Wednesday, 26 September 2018 9:15 PM
*Subject:* Re: [USRP-users] B205 External Reference issue
On 09/26/2018 02:42 AM, Arun kumar Verma via USRP-users wrote:
Hi
We are using B205i-mini and we found that when I am sleclecting
external Ref using set_clock_source("ëxternal"); I am getting
intermodulation components in Hz.
I think supply for the internal oscillator is still on and it is not
compeletly shutting down. Is there any options to switch off the
suppy of ineternal oscillator through some API.
Regards,
Arun Verma
There is only one clock on the B205 -- a 40MHz VCXO. When you switch
to "external", the FPGA implements a clock-steering
"servo" that phase-locks that 40MHz clock to the external reference.
You're probably seeing very low-level clock spurs that appear as a
result of the servo algorithm.
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