[time-nuts] Trimble GPS board

Angus not.again at btinternet.com
Sun Aug 23 05:49:26 EDT 2015

On Sat, 22 Aug 2015 18:25:04 -0400, you wrote:

>rbenward at verizon.net wrote: "See below, here is a 73090
>OCXO (same as on some of those GPSDO boards) powered by +12V."
>You are incorrect in your assumption that the link you have
>supplied shows a 73090 OCXO powered by +12VDC. The BOARD is
>indeed powered by 12VDC (or 15VDC if you read the listing)
>but if you look at all the photos you will see a 3-terminal
>regulator on the bottom of the pc board.


It does indeed have a reg, but as far as I can see it's a 7812 that's
in the picture in the listing. This would also explain why it has a
12V or 15V selector link.

I'm not suggesting that it's a 12V osc - on my 57963-80 it is
definitely fed just 5V from the regulator. I also used 6V for the
power supply.
It also appears just to be a basic, fast warm-up AT OCXO, which fits
in with the short time constant on the GPS control loop.


>The Trimble GPSDO I'm supplying 6.3VDC to had a 5 volt regulator
>that has a measured output of 5.00VDC and the supply pin on the
>oscillator had that 5.00VDC on it, not the 6.3VDC from my supply.
>A continuity check shows a direct connection from the regulator's
>5 volt output directly to the oscillator's supply pin. Because
>of the higher current drawn by the 5 volt oven, running the input
>to the board at 12VDC and wasting all that power as heat would
>not be wise. 6.3VDC makes me happy and they chose a LDO regulator
>for a good reason.
>The one error I did notice is I said the board locked after it
>found satellites but that is incorrect. It does find satellites
>quickly but takes about 10 minutes to lock and that is when the
>10Mhz output is enabled. I did some of my checking around 1AM
>and that is not a good time for clear thinking or writing.
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