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
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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