[time-nuts] 9390 GPS RX
ed_palmer at sasktel.net
Sat Jun 1 13:36:20 EDT 2013
On 6/1/2013 9:47 AM, Mark C. Stephens wrote:
> Yep, Phase plot is like a Saw tooth.
So, despite the 'lock' LED, it isn't locked. Well, maybe something's
locked, but we're not sure what.
> I plugged the house standard as external reference (I am sure I did that already) and it still drifts so there is something wrong there somewhere.
> I also measured the DAC voltage going to the FRK and it's not moving from 0.95 volt.
> Without schematics I am pretty much stuck at this point.
> I doubt if the Schematic for that RX was ever released.
I'd take a shot at reverse engineering the connections to the receiver.
See if you can talk to it or, at least, see if the 1 PPS coming out of
it is actually locked to GPS. Maybe that's what the 'locked' LED means.
> BTW, there are ~120Hz varying on those 1st 2 SMB connectors
> The first is Sine, the second is square.
That's the two that go to the OCXO? You'd have to trace out the OCXO
board to see if that made sense. I would have expected to see a sine
wave output from the board and an EFC DC voltage input. 16.618 MHz could
be divided down to 125 Hz which might be used as a reference for phase
comparison. 120 Hz would work if the crystal was 16.617 960 MHz. Now
that I think of it, that OCXO should be checked to see to see how far
it's drifted over the years. Whether it's supposed to be phase-locked
or free-running it could have drifted out of range.
> So, Plan is to Shelve it, on the off chance someone needs bits or I find a parts donor.
> Bit disappointed really, good looking piece of kit.
> I have about 1100 other projects on at the moment and they are all falling behind..
Yeah, I know what you mean. My problem is, I'm too stubborn to give up
on a project. My project list and workbench suffer from the backlog.
Oh well, it's been fun. Of couse, you now have a working FRK so the
project wasn't a total loss.
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