[time-nuts] Trimble GPS board

Bob Camp kb8tq at n1k.org
Sat Aug 22 15:29:22 EDT 2015


Great information !!!!!

> On Aug 22, 2015, at 11:19 AM, Arthur Dent <golgarfrincham at gmail.com> wrote:
> "Does anyone have any information or experience with this small
> Trimble GPSDO?"
> I had previously posted that what I thought these boards
> were and how they might work and said I was waiting for 2
> of these boards that I had ordered to arrive. Yesterday the
> 2 boards arrived in an Epacket from China. If you order
> more than one board check them carefully on arrival because
> the 2 I received were placed back-to-back with no padding
> in between and a couple of the small SMD components on the
> back side were partially ripped off the pc board. Fortunately
> the damage was repairable and both boards are ok. What I found
> was that there are at least 2 different versions of this GPSDO
> and although both function the same, the location of some
> of the parts differ.
> First, there is the understandable language barrier and if
> the sellers do have information that could help you get the
> board up and running, it isn't included in the English
> listings. Some of the info you can glean from looking at all
> of the photos of the various units for sale on Ebay is just
> from arrows on the photos telling where to connect power and
> get the 10Mhz output. It took me a lot of trial and error plus
> tracing out some of the runs to get to a point of where the
> boards were working as intended.
> The supply voltage required is stated to be 5.6 to 6VDC and
> this goes to an LT1764A low dropout regulator set to 5VDC out
> so my 'guess' is that 6VDC should be the minimum supply voltage
> to make sure the regulator keeps working properly. With the
> multicontact connector facing you you will see a 5A fuse near
> the back right edge of the connector. I soldered the '+' supply
> lead from my power supply (that puts out about 6.3VDC regulated)
> to the left end of this fuse and the '-' supply lead to the ground
> plane on the left of the connector. Using too high an input VDC
> could cause the regulator to dissipate too much heat.

How much current does it pull at turn on? The regulator is only rated 
to 3A so I would *guess* it’s less than that. 

> When the board is powered up with the antenna and the 10Mhz
> output connected you will see no 10Mhz output. There are two
> 2-color LEDs on the board, on top of one version, and on the
> bottom of the other version. One is the ALARM LED and the other
> is the ACTIVITY LED. On power-up both light red then go out
> (if all is well) then the ACT LED stays on solid green for maybe
> 10 minutes until the GPS receiver starts to track satellites. At
> this point the ACT LED starts to flash a slow green and the 10Mhz
> output is turned on. After a few more minutes when the board
> achieves lock the ACT LED starts flashing green at a higher rate.
> On the left front corner of the board is the 1 PPS connector.
> To the right of that connector are 4 unpopulated holes for a
> connector. I traced those out and found 2 went to a RS-232

There’s also this listing that shows an pair of 9 pins tacked on the 
same board:


> chip that appears to be a different type depending on which of
> the boards you receive. The left hole is ground (RS-232 pin 5
> on the computer end), then the next hole is not connected, then
> RS-232 pin 2, then pin 3 being the hole with the square index pad
> on the right. Using a terminal emulator program and 57600 8N1N
> I was able to communicate with the board. Typing '?' will give
> you a long list of all the commands it will accept. For instance,
> 'STAT' and 'POSSTAT' are 2 of the commands that will give you
> info on how the board is working. Typing *IDN? at the UCCM-P >
> prompt returns 57964-60 for my board and POSSTAT shows up to 12
> satellites can be tracked.

Time to get a few mods in on LH :)….

> The date code on my unit is 2009.
> The board seems to work well but the OCXO runs pretty hot so it
> probably isn't a double oven.

I think it’s pretty safe to guess that a GPSDO designed well after SA 
went off for good has a single oven rather than a double oven on it. 


> The multicontact connector probably
> has most of the functions and LED signals available but I couldn't
> see using it so I'll get whatever signals I want directly off the
> pc board.
> -Arthur
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