[time-nuts] Samsung GPSDO : Chinese surplus

mimitech mimitech mimitech at gmail.com
Fri Sep 21 08:25:11 EDT 2018


Hi, Nigel
To select GPS as the default input port, it was required to tie PIN 39 (of
50-pin FPC connector) to GND.

On Thu, 20 Sep 2018 09:55:10 -0400 gandalfg8 at aol.com wrote:
> Subject: [time-nuts] Samsung GPSDO : Chinese surplus
>
>
> These are Samsung's version of the "UCCM" series of GPSDOs.   Lady
Heather now works with them.   I had to tweak the code to handle their
funky/erratic end-of-line sequences... various versions of CR/LF, LF,
LF/CR.   Their STATUS screen and some message responses are also a bit
different.  They do tell you the antenna current.......
>
>
> -----------------------------
>
>
> I'm not sure, but to borrow from Orwell, I do suspect that some Samsung
UCCM modules may be more equal than others, so here's a warning to the
curious, sorry, M R James that time:-)........
>
>
> Anyways, after Greg posted information about these earlier this month I
bought one of the STP2945LF versions from Ebay auction 332792680396 and the
one that arrived a couple of days ago is the actual item currently pictured
in that auction, condition is very good and a flatstrip interface connector
was an unexpected bonus so certainly no problem there.
>
>
> Whether or not I've just missed something and ended up reinventing the
wheel I don't know, but after first believing wrongly that this unit must
be faulty here is what I've found so far......
>
>
>
> The supply voltage seems to be quite critical, inasmuch as the alarm
light is on if the supply is below approx 5.5 volts, it certainly doesn't
like 5 volts, and it comes on again if the supply is increased to just over
6 volts. At the upper limit there's no immediate obvious other effect but
at the bottom limit the unit seems to drop immediately into holdover, this
from observing plots on a Pendulum counter.
> Even when the supply is ok the alarm light is amber rather than green but
not sure what that's trying to tell me. Trying different antennas and even
a resistive load at the antenna socket makes no difference.
>
>
>
> At the moment Lady Heather doesn't seem to be hapy with this one, despite
forcing baud rate and receiver type she just didn't want to know at first
and insisted there was no data to be seen from the COM port, and initially
the unit itself didn't seem to be doing anything very useful either
>
>
>
> However, running it into Hyperterminal did show it booting up at 57600,
8-N-1 as expected, and eventually I discovered that this unit has two
options for Reference type, GPS or EXT, EXT presumably "external" and I
assumed referring to what was supposed to be feeding whatever this was used
in, and it defaults to EXT whenever the unit is started or after a hard or
soft reset. Fortunately it's possible to run a "Ref : Type GPS" command and
the activity LED quickly confirmed that it's now behaving as expected.
>
> If I run a diagnostic:loop command though it's so far always returned a
figure of +1.062E-7 for the OCXO but also states that EXT is "unavailable"
which might even suggest that the EXT input is an expected input to the
GPSDO itself.
>
> Purely speculation of course, and the 1PPS is definitely an output at the
moment...
>
>
>
> Next oddment, trying yet again to let Lady H see it I left the GPSDO
running and terminated the connection in hyperterminal and started Lady H
again with the receiver preset as UCCM, still nothing until I brought up
the command line help screen and then Lady H started taking data in behind
it only to stop again when I closed the help screen.
>
> This was very erratic though, sometimes she'd stay after the help screen
was closed but sometimes lock and sometimes randomly updating, either way
she certainly wasn't having a good day:-)
>
>
> What Lady H did manage to do was to switch the output to the continuous
data stream mode and the only way I've found so far of stopping this is a
hardware or software reset, either of which then sets the Reference typ to
EXT again:-(
>
>
> So that's it for now, still playing but I did think it was worth alerting
other potential buyers as to what they might expect.
>
>
>
> Not all doom and gloom though, and believe it or not I'm even inclined to
recommend it, Lady H has shown over a dozen sats with good signal levels at
times, that's pretty remarkable for here, and it does lock quickly and
conditioning looks good. It would be interesting to see if holdover
improves though, and if it could be persuaded to default to GPS at start up
that might perhaps be a bit more useful:-)
>
>
> Nigel, GM8PZR


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