On 09/30/2018 03:55 AM, Arun kumar Verma wrote:
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.
DO NOT DO THIS.
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> <mailto:mle...@ripnet.com>
*To:* Arun kumar Verma <arun.ve...@eiwave.com>
<mailto:arun.ve...@eiwave.com>; "usrp-users@lists.ettus.com"
<mailto:usrp-users@lists.ettus.com> <usrp-users@lists.ettus.com>
<mailto: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>
<mailto:usrp-users@lists.ettus.com>
*To:* usrp-users@lists.ettus.com <mailto: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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