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

[Giuseppe Marullo]

> 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:
http://electronics.stackexchange.com/questions/247256/gps-splitter-with-200ohm-dc-load-and-50ohm-rf-impedance-on-all-ports
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
(...omissis...)
 >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 
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>
 >>tipok.org.ua
 >>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 
purpose.

 >>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...