Re: [Discuss-gnuradio] external clock issue with B100 + WBX

[Guy Holtzman]

I Checked the levels with the clock connected to the USRP ( and without)

The levels are fine ( about 600 mV rms on the scope)

additionally, I disconnected it from the load (USRP) to see if the level changed. and they did (proving the cables are connected to a load).

the problem remains,

is there a command that could check if the USRP is locked to the external clock?

what is the best way to debug this and to find the root cause?

Thanks for your help,

Guy

On Sun, Jun 2, 2013 at 9:55 PM, Marcus D. Leech <address@hidden> wrote:

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

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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

_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio