Samsung GPSDO 

So the next project is a Samsung GPSDO (STP2945LF / STP 2878 LF) I bought from ebay for about $30 + Shipping.
It's quite similar to the Trimble and Symmetricom GPS devices, but also very different.
For now I have it running with good results but that was not so easy, and not Plug&Play.


Unlike the buyer would like you to believe, not every unit is usable when plugging it in.

For me the unit did not lock even after have it running for 3 day's in a row, so that was not good.
I did not have the break-out board with the 50pin flat cable with it, and the used SMD devices are to small to attach a wire to it.

So I ordered this board from China. 


First we need to do is to get power on the board.
For the samsung there is little information on the web, but the boards don't really differ very much from the Symmetricon where more units are available and so also much more (ham) info is found.

One of the site's is this one:


Of course there al 40+ pages at the moment I write this, so the main thing is to connect the power of course:

Now it was easy to attach the serial port to it, and check with the PC what the status is.
       - UCCM Slot STATE -

1-1 #Now UCCM STATUS ----------------------------[Alarm]
1-2 #Before UCCM STATUS -------------------------[OCXO Warm]
2-1 #Reference Clock Operation ------------------[Not Used]
2-2 #Current Reference Type ---------------------[Ext Clock]
2-3 #Current Select Reference -------------------[NOT SELECT][Ext ?]
2-4 #Current Reference Status -------------------[Unavailable]
    #GPS STATUS ---------------------------------[Unavailable]
    #Priority Level -----------------------------[EXT->GPS]
    #H/W FAIL -----------------------------------[NONE]
    #OPERATION ALARM ----------------------------[EXTREF]
    PLL STATUS ----------------------------------[Disable]
    Current PLL MODE ----------------------------[OFFSET OBSERVATION MODE]
"Command Complete"
So it as warm, but programmed to use it with an external signal as reference (why?) .

Searching the internet just did not gave me much solutions, but did find out that many other had similar problems. one of the solutions was to use a external programmer to send the needed commands to the board. later more about this solution.

Edit 2020-02-11: I got a message from Jan SM4UKU, with the hint that the board should have a bridge from pin 39 to GND.
In that way you enable the settings for internal GPS reference.

More information also on this very useful website:  


Now for lady Heather, not very high-tech looking program, but useful so we need this.
Google it and you will find version 5.0 from KE5FX, but not working on our device... :-( 

After logging into the EEVBLOG i found out that there is a 6.14 beta version which is available as download (Will put it on my site).

So, now it was useful.:


This is my status after running half a day.
My horizon for the GPS satellites starts at about 35-45 degree so there is room for improvement. But we have a lock and the first survey was done and the signal is stabilizing. 
I do have a antenna error, despite the fact there is 5V and about 20mA.

maybe it expects more power drain, I will test this soon.

Updates will/may follow.