[App_rpt-users] RTCM voter problem - SOLVED

Sat Apr 9 17:36:37 UTC 2016

I thought you had to use an external, GPS-synced  9.6MHz clock reference in
order to negate clock jitter for simulcasting to work properly (that's been
thrown around on this mailing list before).

Either way, how is a customer supposed to know if they are getting an RTCM
with an in-spec crystal? Has the plans for the PCGM module been tossed?
Are there plans for provisioning interfacing for injecting an external
9.6MHz into the RTCM in lieu of it's internal crystal? These are questions
I have heard others ask before, and would love an answer to.

Thanks!

On Saturday, April 9, 2016, James Cizek <james.m.cizek at gmail.com> wrote:

> Well, after many of you offered your time and thoughts on my voter
> problem, Jim WB6NIL graciously donated a couple of hours of his time to
> remotely help me and he uncovered the problem.
>
> All 5 of my RTCMs were purchased within the last 6 months, and I suspect
> all 5 have the same problem (will verify that today)   The problem is that
> the microprocessor crystal is running too fast!   There is 9.6Mhz crystal
> that drives the MPU,  on the particular unit that Jim helped me diagnose,
> it's running 2.5 khz too fast.  There is a sanity check in the firmware
> that makes sure the correct number of samples were taken in the last second
> (it's supposed to be 8000) and fails if the sample is incorrectly sized
> (mine is taking 8003 samples).  Jim helped adjust the code to be more
> tolerant of the sampling error and my whole system instantly worked.
>
> I have since tested it with ALL my GPSs (they all work great!)  So I now
> have everything working, including the voting.
>
> I haven't contact Micro-Node about it yet.  Jim told me that voting should
> work fine but this clock error would probably not be acceptable for
> Simulcast (something we have no plans on doing as of now).  Since mine are
> deployed at mountain top sites, I'll probably pursue a crystal that is
> running at the correct frequency and use "standard" firmware so that if the
> decision is ever made to play with simulcast, I won't be right back in this
> same boat.
>
> Thanks to all that helped out, and a HUGE thanks to Jim for taking the
> time to troubleshoot this.
>
> BTW- This clock error will NOT effect the RTCM in mix client mode, it only
> affects it in voting or simulcast mode!
>
> Thanks all, have a good weekend.
>
> 73
> James
> KI0KN
>
> On Tue, Apr 5, 2016 at 12:56 PM, James Cizek <james.m.cizek at gmail.com
> <javascript:_e(%7B%7D,'cvml','james.m.cizek at gmail.com');>> wrote:
>
>> Hi all,
>>
>> I posted this problem many months ago and I came to the conclusion at
>> that time that it was my 1PPS signal from the GPS into the RTCM that was
>> the problem.  I have changed hardware now to fix that and I still have the
>> problem so I am suspecting a config issue and hope someone will have an
>> idea.
>> This is on a stock DIAL box.
>>
>> RTCM is setup and working great as a standard node.
>> Everything is working great on the repeater as long as RTCM is in
>> non-voter mode.
>>
>> I have the chan_voter module loading in modules.conf.
>>
>> Here is my voter.conf:
>>
>> [general]
>> port = 667
>> buflen = 200
>> password = blah
>>
>> [1115]
>> Horsetooth = blah,transmit
>> plfilter = y
>> txtoctype = none
>>
>>
>> I am happy to share any other config if requested.
>>
>> In the RTCM menus, I have a static IP, I have the voter server IP, all
>> the approriate IP fields filled out. As mentioned, the RTCM works fine with
>> the asterisk server when it's in non-voter mode.
>>
>> Here's the way I am testing:
>> Verify RTCM menu item 10 is set to (2) None.
>>
>> Boot server, then boot RTCM.  RTCM console says:
>>
>> GPS Receiver Active, waiting for aquisition
>> GPS signal acquired, number of satellites in view = 9
>> 04/05/2016 17:58:17.560  Time now syncronized to GPS
>> 04/05/2016 18:13:18.580  Host Connection established (Pri) (10.16.1.240)
>>
>>  I have a very nice, clean, 5Volt 1PPS signal going to pin 7 on the
>> DB15.  Verfied with o-scope.
>>
>> as soon as I change menu item 10 on the RTCM to either a (1) or a (0)
>> instead of (2),  I *instantly* get this on the RTCM console:
>>
>> 04/05/2016 18:44:13.660  Lost GPS Time synchronization
>> 04/05/2016 18:44:13.660  Host Connection Lost (Pri) (10.16.1.240)
>>
>> and it sits there forever and never re-establishes connection to the host.
>>
>> Here is a snippet of the GPS output:
>>
>> $PFEC,GPtps,160405181603,1,0,1,150701000000,00,17,160405165607,1891,238580
>> $GPGGA,181603,4020.9810,N,10506.4515,W,0,07,00.00,001566.7,M,-020.0,M,,
>> $GPGSV,2,1,08,03,53,215,46,07,09,253,37,09,28,305,39,16,63,126,43
>> $GPGSV,2,2,08,22,26,178,44,23,60,316,43,26,52,066,41,31,17,061,34
>> $GPRMC,181603,V,4020.9810,N,10506.4515,W,,,050416,008.9,E,N*1A
>> $PFEC,GPtps,160405181603,3,0,1,150701000000,00,17,160405165607,1891,238580
>> $GPGGA,181604,4020.9810,N,10506.4515,W,0,03,00.00,001566.7,M,-020.0,M,,
>> $GPRMC,181604,V,4020.9810,N,10506.4515,W,,,050416,008.9,E,N*1D
>> $PFEC,GPtps,160405181604,3,0,1,150701000000,00,17,160405165607,1891,238581
>> $GPGGA,181605,4020.9812,N,10506.4495,W,1,07,01.73,001573.3,M,-020.0,M,,
>> $GPRMC,181605,A,4020.9812,N,10506.4495,W,,,050416,008.9,E,A*0F
>> $PFEC,GPtps,160405181605,3,0,1,150701000000,00,17,160405165607,1891,238582
>> $GPGGA,181606,4020.9812,N,10506.4494,W,1,07,01.73,001573.2,M,-020.0,M,,
>> $GPRMC,181606,A,4020.9812,N,10506.4494,W,000.0,283.2,050416,008.9,E,A*06
>>
>>
>> I am just not sure where to go from here.  I can't seem to find anyone
>> that's had any problem like this or what might be causing it.
>>
>> I have tried 5 different RTCMs and 5 different GPSs from 3 different
>> manufacturers.
>>
>> Any suggestions on what I might be missing?
>>
>> Many thanks for any help anyone can offer!
>>
>> James
>> KI0KN
>>
>
>

-- 
KJ6QFS
Sam Skolfield
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