Dan wrote:
My gut feeling is you are right about the GPS time base being sensitive. It would be fun to hack into this and try clocking it off the OCXO, but I'm not there yet! :)
One interesting way would be to use the disciplined OCXO output to drive a DDS synthesizer set to the GPS unit's clock frequency (which, I'm assuming, is not the same as the OCXO frequency). This approach has a number of potentially large problems (delay, spurs, DDS resolution, to name just 3), so I'm doubtful that it would work well -- but I do think it's worth trying, just because it's so simple and cheap ($3.85 ebay DDS board) and potentially instructive.
I might try some good old 'overkill' and put the GPS in it's own heavy aluminum box. It's been a thought for a while, and should address the thermal integration and time constants you referred to.
Insulate the GPS card from the box (use nylon or teflon standoffs with no "through" metal screws), and insulate the box from anything solid (same way); i.e., only air can change the box temperature, and only air can change the GPS card temperature. Signals and power should go through bulkhead connectors and feedthrough caps on the box walls, with "pigtails" to get from there to the GPS card. You probably don't need anything too massive, just whatever cast Hammond box it will fit in (allow for the connectors and feedthrough caps!!). You can always add mass later (bolt slabs of aluminum to the outside of the box) -- but in this application, you shouldn't need to.
Best regards, Charles _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
