# N210 Unsuccessful Ref Lock

**URL:** <https://www.ruby-forum.com/t/n210-unsuccessful-ref-lock/220506>\
**Category:** GNU Radio\
**Created:** [June 12, 2012, 1:05am UTC](https://www.ruby-forum.com/t/n210-unsuccessful-ref-lock/220506 "2012-06-12T01:05:59Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\
**Post date:** [June 12, 2012, 1:05am UTC](https://www.ruby-forum.com/t/n210-unsuccessful-ref-lock/220506/1 "2012-06-12T01:05:59Z")

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Hi all,

My research group is continuing our setup of two servers with multiple  
N210s for a GNSS application. Each server will have 4 or 5 N210s  
recording  
RF data at frequencies of interest. All are to be locked to the 10MHz  
reference and 1 PPS output from a Septentrio PolaRxS. I have  
successfully  
tested our PPS arrangement using test\_pps\_input. However,  
test\_dboard\_coercion sometimes reports an unsuccessful lock to our  
external  
oscillator. The number of unsuccessful locks varies with the inputs to  
test\_dboard\_coercion:

Set1: “–rx --ref external” reports an unsuccessful ref lock at 1500MHz  
Set2: “–rx --ref external --no\_rx\_gain” reports an unsuccessful ref  
lock  
at 1500, 1550, 1700, 1750, 1800, 1850, 1900, 1950, and 2000MHz.

These unsuccessful locks are intermittent. The results for Set2 don’t  
worry me so much: we’re always running at high gain when recording.  
What  
is the cause and is there a good solution to this problem? Our plan is  
to  
have all N210s writing constantly to a ring buffer, but only writing to  
file when triggered by an external source. The reference lock is  
critical  
since we’re studying GNSS signals. Any help is appreciated. I know  
this  
list usually hits it out of the park, so I’m looking forward to your  
responses!

Thank you,  
Ryan

Setup: Dell PowerEdge R510 running UHD 3.4.2 on Ubuntu 12.04 server.

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<div class="post-metadata">

**Author:** ![Ryan\_Wolfarth](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/6f9a4e/32.png) [@Ryan\_Wolfarth](https://www.ruby-forum.com/u/Ryan_Wolfarth)\
**Post date:** [June 12, 2012, 1:13am UTC](https://www.ruby-forum.com/t/n210-unsuccessful-ref-lock/220506/2 "2012-06-12T01:13:34Z")

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> help is appreciated. I know this list usually hits it out of the  
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)  
> After splitting your 10Mhz reference, what is the power going to each  
> N210?

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**Author:** ![Ryan\_Wolfarth](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/6f9a4e/32.png) [@Ryan\_Wolfarth](https://www.ruby-forum.com/u/Ryan_Wolfarth)\
**Post date:** [June 12, 2012, 7:21pm UTC](https://www.ruby-forum.com/t/n210-unsuccessful-ref-lock/220506/3 "2012-06-12T19:21:50Z")

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The clock signal has not been split yet: I’m only testing one N210 to  
verify a reference lock. We will be using a SRS FS735 distribution  
amplifier for clock splitting. It outputs 13+/-1 dBm to a 50 Ohm load  
from  
each output.

The current dboard is an RFX1800, but we will be using a combination of  
1200s and 1800s depending on the signal we’re capturing. We changed the  
sleep time in test\_dboard\_coercion to 5 seconds instead of 1. I’m going  
perform some more thorough testing, but this looks like a good fix!

Thank you,  
Ryan

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<div class="post-metadata">

**Author:** ![Ryan\_Wolfarth](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/6f9a4e/32.png) [@Ryan\_Wolfarth](https://www.ruby-forum.com/u/Ryan_Wolfarth)\
**Post date:** [June 12, 2012, 7:53pm UTC](https://www.ruby-forum.com/t/n210-unsuccessful-ref-lock/220506/4 "2012-06-12T19:53:23Z")

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On 06/11/2012 05:18 PM, Ryan Wolfarth wrote:

> The clock signal has not been split yet: I’m only testing one N210 to  
> verify a reference lock. We will be using a SRS FS735 distribution  
> amplifier for clock splitting. It outputs 13+/-1 dBm to a 50 Ohm load from  
> each output.
> 
> The current dboard is an RFX1800, but we will be using a combination of  
> 1200s and 1800s depending on the signal we’re capturing. We changed the  
> sleep time in test\_dboard\_coercion to 5 seconds instead of 1. I’m going  
> perform some more thorough testing, but this looks like a good fix!

Yea, sorry. It looks like there were a few things a little screwy with  
the lock detect checking. I will push something tomorrow to make it a  
little more consistent.

Thanks!  
-Josh