UCCM and UCCM-P GPSDO modules - lots of questions - Page 1
Forum section: electronics / general

author: tkamiya
author_rank: Super Contributor
timestamp: February 03, 2020, 12:59:38 am
content: I am now addicted to GPSDO. They are multiplying in my lab and about to take-over a rack.I have been seeing small GPSDO modules with narrow pitch connector, all in about the same size on eBay quite a bit. There seems to be models from just about every single GPS manufacturers. Just recently, I leaned they are commonly referred to as UCCM modules. Other than the name, I seem to be unable to find any documentations that describe this type of modules. (individual docs do often exist)I've been searching but I cannot find any specifications for UCCM modules. Other than size, how common are they? Do they share same pin out and commands? Can I, for example, take out Samsung module and place Trimble module and they work just the same? Performance wise, how do they compare? What's the difference between UCCM and UCCM-P? P seems like a superset of UCCM, but is it? What is the purpose of these modules? Since sizes are the same, I thought they are meant to be replaceable.If you have any pointers, especially pointer for a doc, I would be very appreciative. Any comment or bits of information is great too, as I know nothing at this point.

author: ZigmundRat
author_rank: Regular Contributor
timestamp: February 03, 2020, 05:17:44 am
content: A rather extensive threadwww.eevblog.com/forum/projects/a-look-at-my-symmetricom-gpsdo-(ocxo-furuno-receiver)on these exists. I participated in that and there’s some really good info there. It should keep you busy for a little bitIIRC the uccm were part of the timing subsystem for a Samsung cellular system. Trimble and Symmetricom were both providers. I think the uccm vs uccm-p relates to the release level (or generation) of the solution.(And BTW, I also went down the GPSDO rabbit hole. I just took a quick mental inventory and got to 18, including 5 Rb versions)Edit: Fixed busted link

author: tkamiya
author_rank: Super Contributor
timestamp: February 03, 2020, 03:02:26 pm
content: Thanks! I actually knew of your thread. How do you like yours so far?I also read from few other threads, many of these modules arrive damaged as a result of salvage nature of these, and rough handling by the salvage workers. ME TOO, on Rb. I have 4 different kinds here. As they were quite affordable, I couldn't help myself. I am currently working on steering PRS-10 by Trimble, so in essence, making a Rubidium GPSDO. So far, it is working well. Very likely, this will become my next lab standard.Thanks again for your reply!Taka

author: thinkfat
author_rank: Unknown
timestamp: February 03, 2020, 03:21:10 pm
content: I own three of those UCCM modules myself - one each made by Samsung, Trimble and Symmetricom. They are definitely interchangeable, I made a small breakout board with integrated power supply and connectors for various serial interfaces and it works on each of the them. They're all pretty well supported by Lady Heather, too.

author: tkamiya
author_rank: Super Contributor
timestamp: February 03, 2020, 03:29:13 pm
content: Nice! Do show the photos of your project....?I was wondering something... I have tons of GPSTM by Nortel. There are two versions. Ones made by Trimble, which is a customized version of T-bolt, and the other, made by Symmetricon. The latter version has some significant jitter. This is because there is no integer multiple between OCXO and the output. I'm assuming, since these UCCM modules have 10MHz OCXO, there is no such problems. Do you concur?Taka

author: thinkfat
author_rank: Unknown
timestamp: February 03, 2020, 03:39:43 pm
content: You can find most of it in this thread:https://www.eevblog.com/forum/projects/question-on-buck-converter-layout/msg2772528/#msg2772528Regarding measuring jitter - I seriously lack equipment for measuring that. I was looking into buying either the TAPR TICC or a 53131A counter. In theory, the jitter on the 10MHz output should be as good as the OCXO is specified. Regarding the 1PPS, I don't know if these modules generate the 1PPS from the 10MHz or if they just channel out the 1PPS from the GPS receiver - that would be pretty bad, though.

author: tkamiya
author_rank: Super Contributor
timestamp: February 03, 2020, 03:54:32 pm
content: I cannot measure jitter but I could easily see it on dual trace oscilloscope. I triggered it on known-good-and-stable timing source, and I could clearly see the signal jumping quite badly.I really like how you built your project. Very clean design. As far as PCB goes, I don't have the knowledge and technique to use CAD. I did do quite a bit of hand-routing way back in the days though. Right now, I'm using linear supply for all timing devices. My PRS-10 GPSDO box gets quite warm with two major heat source in a 2U box. My later designs use external power source. It is one of my to-do to come up with a filter design, so I can use off-the-shelf switching mode power supplies. They run much more efficiently.Thanks for sharing.

author: FransW
author_rank: Frequent Contributor
timestamp: February 04, 2020, 03:52:46 pm
content: I found the answer of E. Palmer:Re: GPSDO with Rb and XO « Reply #49 on: January 15, 2020, 05:10:33 am »quite clear.Frans