Some 1PPS signals are so short they are difficult to detect. So then people have rigged up pulse stretchers that lengthen their duration.
This situation is actually fairly common.
Thank you for the reply I have grounded pin 38-39. ( I had found that pin out a few days back thanks again this is touch to find more post will make it easy to find the pinouts) What I have read it seems (from others post) that 1 PPS comes up with out any effort or commands. My unit is locked it has 10+ gps sat locked. It is a solid 10 MHz locked output. but still nothing out of the 1 PPS port (not that I needed it but it would be nice to have). The unit is connect to lady heather and tried all the enable and disable 1 PPS commands. I have a friend that has a board he has not tried and he will bring over for comparison. I have read the time nuts article, feel I have gleam everything I can from that reference you provided it seems that Nigel did nothing to enable 1 PPS? For sure you need to ground pin38-39 to use GPS or the device alarms and only a sub standard 10 MHZ reference is output.. I am not sure where the other post is but will search this forum for it.. KC0SKM
Also, the supply voltage must be almost exactly 5.5 volts with the full load. Which requires a fairly robust power supply.
Samsung UCCM 1pps is not very short. Around 50us.
This is not from just same model but "mostly compatibe".
Supply voltage need be inside 5.30 - 5.70 V measured from board. Best place to measure is GND and on board Fuse end. This flat film cable have resistance and it is best all GND and all VCC 5.5 V terminals need be connected for avoid voltage loss. In startup it takes nearly or even over 2 A current and after temp is ok still around 0.8-0.9A.
Here 1pps out image. Directly from J4 to oscilloscope HiZ input. It can also terminate 50ohm but voltage is then bit over 1 V (in mine all three units around 1.17 V. Upper window can see 2 1pps pulses and bottom just one zoomed.
Btw, there is also one other way to get "pps" out. 50pin conector pin 2. It is fast UART TX TTL. It start message every second. If just detect start it can use as pps. I can not now check if it give out really 1 message per second or 1 message every 2 second. But this I remember when I have measured that it is sync with 1pps.
Also, of course, this J4 1pps is tightly sync with 10MHz Sine out from J3.
1PPS out from Samsung STP2878LF