On 06/02/2013 02:49 PM, Guy Holtzman wrote:
I have two USRP B100 and I am trying to sync them
for that I have connected them both to reference and 1pps from the
same source
the source is a rubidium standard source reference
it has a 10MHZ 1Vrms 50 ohm sine and 1pps outputs. I have tested it
with a scope to see if its stable.
for my test I transmit from one USRP B100, and receive from the other
USRP.
I configured both devices for:
clock source: external
time source: external
sync: unknown 1pps
tested the output with WX GUI FFT Sink on the Rx side
whenever I set the clock source to external on the receiver side,
instead of getting a carrier, I get a distorted signal: the I and Q
are not constant envelope, as they should be.
whenever I set the clock source for default, I get a carrier, but it
is shifted a few 100s of hertz from the wanted signal and it changes
every a few 100s of hertz (it is not constant)
I am using the latest version of GNU Radio
I didn't see any warning or error message when disconnecting the 10MHz
clock ref.
I did see an error message when I disconnected the 1pps ref.
is this a known problem? is this expected? if not, what am I doing wrong?
I am adding the grc files
here is the log (it seems fine, and look identical for Tx and Rx):
Generating: "/home/guy/Documents/top_block.py"
Executing: "/home/guy/Documents/top_block.py"
linux; GNU C++ version 4.6.3; Boost_104800; UHD_003.005.003-78-g49a4929b
-- USRP-B100 clock control: 10
-- r_counter: 2
-- a_counter: 0
-- b_counter: 20
-- prescaler: 8
-- vco_divider: 5
-- chan_divider: 5
-- vco_rate: 1600.000000MHz
-- chan_rate: 320.000000MHz
-- out_rate: 64.000000MHz
--
-- 1) catch time transition at pps edge
-- 2) set times next pps (synchronously)
Regards, Guy
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Look at the 1PPS and 10MHz signals on the scope with them connected to
the B100 -- are the levels still in range for the input spec?:
http://files.ettus.com/uhd_docs/manual/html/usrp2.html#ref-clock-10mhz
The N2XX notes contained there should apply to the B100 as well.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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