I have tried that but it increases when i reduce amplitude , in fact for DC
coupled ref i am getting best result.
I have checked the schematic and in that if i remove R37 and R38 then my
internal clock will disconnected but i am not sure whether board will work with
only external clock or not. Can you verify this. I want to disconnect internal
clock and want only external clock as there I am not getting any drift.
Arun
From: Marcus D. Leech <mle...@ripnet.com>
To: Arun kumar Verma <arun.ve...@eiwave.com>; "usrp-users@lists.ettus.com"
<usrp-users@lists.ettus.com>
Sent: Sunday, 30 September 2018 2:19 AM
Subject: Re: [USRP-users] B205 External Reference issue
On 09/29/2018 02:20 PM, Arun kumar Verma wrote:
Hi
Please find the screenshots as you have asked. One image is when we are
setting ref to internal but external not connected that time it is clean and
other images is when we are connecting external ref .
Regards, arun verma
Does the magnitude of this small spur diminish if you reduce the amplitude of
your external reference?
From: Marcus D. Leech <mle...@ripnet.com>
To: Arun kumar Verma <arun.ve...@eiwave.com>; "usrp-users@lists.ettus.com"
<usrp-users@lists.ettus.com>
Sent: Wednesday, 26 September 2018 11:56 PM
Subject: Re: [USRP-users] B205 External Reference issue
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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