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A look at my Symmetricom GPSDO / 10MHz reference (OCXO + Furuno receiver)

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metrologist:
Nine green SV's, I guess  the survey completed OK. LH stopped upping the % at 99% and then it went back to Position Hold mode, operation mode stays Locked, PLL went Lock, and TFOM was 2.

metrologist:
Hey all. One of my UCCM boards is not reporting OSC data (stuck at 0.000) and the PLL stays at INIT. I do get DAC and PPS values, however. Do all of these units self report OSC and PLL lock status? This one has much older firmware, in the v1.x range. I'm wondering if this could be a hardware issue or firmware just not supporting the feature?

Briain:
Hi folks

Firstly, my first post must begin with a huge thank you to all the contributors to this excellent and fascinating thread, and atop that, a particularly mega-huge thank you to texaspyro for the wonderful LH!!

Pictured below is my recently installed Trimble 57860-20 GPS Bullet antenna (no expense spared on the Shakespear S/S poles, but the weather here can get really quite vicious) and the view behind it (looking to the north) shows part of Edinburgh (Scotland) with the a small section of the River Forth (just visible) and the Fife hills visible in the background. (Edit: I just noticed that the blurry thing to the right of the lower U bolt is actually Edinburgh castle; sorry about the poor image quality, but to be honest, it really is rather a tedious building, so it's best seen from a half-decent distance.)



Below shows a screen-shot from LH with the GPSDO's elevation mask temporarily set at 0 deg (just to obtain a picture of what it could see). I planned it all to give me a 20 deg clearance (and the elevation mask now set to 20 deg) and other than some pesky trees to my east (fetch me a chainsaw, immediately) I pretty much achieved my goal.



I'm currently building a linear regulated multi-rail PSU for my recently procured Trimble Thunderpants, so I will soon have two units permanently installed and running, so I'm now another one who has been fully infected by the GPSDO bug!

Once again, a huge thank you to all concerned!   :)

Bri (GM8PKL)

Briain:

--- Quote from: metrologist on September 06, 2017, 06:00:56 am ---Hey all. One of my UCCM boards is not reporting OSC data (stuck at 0.000) and the PLL stays at INIT. I do get DAC and PPS values, however. Do all of these units self report OSC and PLL lock status? This one has much older firmware, in the v1.x range. I'm wondering if this could be a hardware issue or firmware just not supporting the feature?

--- End quote ---

Hi metrologist

I have one of the Trimble UCCM boards on loan (from another forum member, GM8BJF) and I am aware that he had an issue with the antenna power feed and comms, so I believe that he picked up 5V from elsewhere to feed the antenna and it all then sprung into life, but this also one displays the same outputs (on LH) as you have described in your post (and in addition, after power up you have to press the MACT button to get the 10 MHz output, but it is actually locked). To check it, I have compared its 10 MHz to a fully functional Symmetricom (also borrowed from GM8BJF) and despite these odd conditions, the Trimble oscillator does appear to be fully 'under the whip' (I looked at the two waveforms on a 'scope and they remained perfectly in step over several days).

We had assumed the odd readings on LH were due to the antenna feed modification (and the Trimble thinking there was an antenna issue), so perhaps your results are related to a vaguely similar antenna communications related problem (though not to the extent that you had to arrange a 5V feed to it)?

I guess it could be down to a very early firmware build, but I have read the entire thread and from memory, I don't think that I've seen any other similar posts (which you'd expect to see if it was a firmware build issue) but I'll look at 'mine' very soon and report back with the F/W version installed on it; the unit is running in my cellar - a nice stable environment - and the Raspberry Pi it normally interfaces to is being temporarily used elsewhere, but it will be replaced very soon.

Bri

metrologist:
Thanks Briain.

Functionally it seems OK. Comparing two units on the scope, I think I recall the units would start to deviate about 180 degrees, as if one went into a tuning routine. Over several hours they would appear locked, but by morning I would notice the separation by leaving my scope on infinite persistence. Once I caught them drifting apart, it looked like one would tune end-to-end and then return to lock.

I don't have any real good equipment (probably more limited by my ability right now) to measure the stability other than that method. I was thinking of clocking the two referenced to a free-running OCXO.

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