[time-nuts] Has anybody checked this? GPSDO in kit

Bryan _ bpl521 at outlook.com
Mon Oct 31 05:22:24 EDT 2016

Seller probably meant TSIP. This probably means he is using the end connector on the board and populating the RS232 connectors on the front of the unit with the various USART outputs that are available on the end connector. I note one of the RS232 connectors has a pin identified as 1pps and this is what is available from the end connector as well.


NMEA like commands are available on the Symmetricom unit by tapping into a pin on the Furuno GPS receiver. I suspect the Trimble is the same, but the seller is not using this option (perhaps not available with a Trimble). I say "like" as the NMEA statements if I recall are missing the checksum. Not a big deal but most of the monitoring programs expect to see it for them to work. Although you can easily view the NMEA statements using a terminal program. There is a few PIC, Arduino projects out there that can take the NMEA statements and display on a LCD, GLCD. I am sure you probably saw a few on the EEVblog forum.


From: time-nuts <time-nuts-bounces at febo.com> on behalf of Giuseppe Marullo <giuseppe at marullo.it>
Sent: October 30, 2016 7:26 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Has anybody checked this? GPSDO in kit

> e) Which is the antenna signal level (dBm) that this unit require
>   to operate properly?>>
>>The antenna you referenced should be fine. I would hazard to guess<g> that antennas a re a whole separate topic. The gain should be fine. What you need is a clear unobstructed view of the sky. I am pretty close to the window, with somewhat easy access to the roof. A 5m pole would pull out the antenna over the roof from the balcony(12m length total, worst case). No taller building around for several hundreds meters.
Having a more precise required signal level would help. SAT cables are mismatched but generally cheaper and able to play nice with cheap splitters, but to play safe I should stay with more expensive cable. LMR-400 sure original is a Tiffany item, here. Lot's of LMR-400 "equivalent" and not even cheap. Ouch.

 >>As for splitting remember that it is a active antenna and expects 5
volts so not sure if the Wilkinson splitter would work??.
Since yesterday I was thinking Wilkinson were a brand of shaving blades!
Seems yes, according to this schematic:

GPS splitter with 200ohm DC load and 50ohm RF impedance on all ports<http://electronics.stackexchange.com/questions/247256/gps-splitter-with-200ohm-dc-load-and-50ohm-rf-impedance-on-all-ports>
How can the GPS400 signal splitter provide a \\$200~\\Omega\\$ DC load and \\$50~\\Omega\\$ RF load to GPS receivers on all four ports? Most GPS receiver modules require an active antenna. As a result,...

This one takes into account sensing for antenna too, so I hope the
answer is yes.

 >> I would be interested as to what others have to say about splitting
the antenna. Have read that a common television satellite antenna
splitter commonly found on Ebay can be used, but the impedance may be 75
ohms and the connectors would have to be changed.
If they work, it could be a cheap option, but I've always seen them with
F connectors, so it could be not worth it.

 > b) which is the difference between the Symmetrical and Trimble
 >understood seems that Trimble does not initiate a Survey at power on.
 >>I had the Symmetricom so can't tell you much about the difference
other that from what other posters have contributed they are very close
to if not identical in many respects.Not having to complete another
survey on >>power up is a definite plus on the Trimble, but I found that
it can complete a survey on the Symmetricom quite quickly.
Ok, thanks.

 >>There is a number of serial ports on these boards. Looking at the
fifth picture on the ebay link, at the top left corner next to the SMA
connector just below R13 is a vertical row of holes. That is the main
serial connection and >>it is at TTL levels. There is other serial
connections available on a ribbon like connector at the end of the
board. Posts on the EEVBlog show where and the pins on the ribbon
connector and what they do. One poster on >>EEVblog probed the ribbon
connector and identified the pins. http://tipok.org.ua/node/53. Some of

Trimble/Symmetricom UCCM GPS Receiver 50-pin connector ...<http://tipok.org.ua/node/53>
Introduction. This page describes the pinouts of 50-pin connector, avaliable at "Trimble 57963-C" and "Symmetricom UCCM 089-03861-02" boards, which can be bought on Ebay.

the UART are high voltage, others TTL
 >>[http://tipok.org.ua/sites/default/files/gps_rx_lores.jpg]<http://tipok.org.ua/node/53>Trimble/Symmetricom UCCM GPS Receiver 50-pin connector ...<http://tipok.org.ua/node/53>

Trimble/Symmetricom UCCM GPS Receiver 50-pin connector ...<http://tipok.org.ua/node/53>
Introduction. This page describes the pinouts of 50-pin connector, avaliable at "Trimble 57963-C" and "Symmetricom UCCM 089-03861-02" boards, which can be bought on Ebay.

 >>Introduction. This page describes the pinouts of 50-pin connector,
avaliable at "Trimble 57963-C" and "Symmetricom UCCM 089-03861-02"
boards, which can be bought on Ebay.
 >>Unfortunately they don't show the backside of the board in the Ebay
link, but I strongly suspect as the main serial connection does not look
populated by any wiring in the picture, they are tapping into the rx pin
of the GPS >>receiver as the source for one of the RS232 connectors.
This is a source of NMEA statements and is documented on the EEVblog.
I asked the seller to provide docs, he was quick to answer but still
nothing about the specific stuff the enclosure does. A Chinese would not
populate a connector for nothing, if it's there there should serve a

 >>You can't send any commands put it does send out a continuous stream
of useful NMEA commands that make it a ideal source for a DIY project to
add a display. Once you receive your unit and connect it to your pc you
will >>(should) see a stream of NMEA commands from one of the RS232 ports.
Let's wait and see what will come up. He said it is not NMEA, but TIPP,
well not exactly TIPP but similar (!??!!). My bad English strikes again...

 >>Hope this helps. I unfortunately toasted mine, and was contemplating
about picking up another one.
Sorry to hear that. Hope you either fix or replace it.

Giuseppe Marullo
IW2JWW - jn45RQ

PS: I nevertheless bought the clock kit with a GPS antenna from
qrp-labs, with enclosure and GPS antenna but not the frequency
reference(yet). Once both will work I will nag you about how to easily
compare the two...

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