Hi Tom, You may have missed TVB's post yesterday, quoted below. A "hanging bridge" is an area on a timing receiver's plotted sawtooth correction value that stays on one side of phase zero for some period of time. As a result of this "bias", a GPSDO that is not corrected for sawtooth will probably have at least a phase shift in its output frequency during a hanging bridge. It's not so bad on the newer 10ns receivers as it was on the older +/-52ns Oncores. If one could prevent these hanging bridges, an uncorrected GPSDO would likely track phase better. Tom suggested to detect when the bridge forms and give it a shot of heat. I suggested to vary the oscillator's frequency by periodically heating and cooling it.
Tom's post: "Sure. In fact you can loosely phase lock it to GPS that way. Your xtal doesn't need to have an EFC pin. You are using external temperature as a replacement for EFC. Call it TFC (temperature frequency control) instead. You can't get much simpler than that. Make sure to use a plain XO (not a TCXO or OCXO). I used a resistor heater to bust hanging-bridges: http://leapsecond.com/pages/vp/heater.htm /tvb" >________________________________ > From: Tom Holmes <[email protected]> >To: 'Discussion of precise time and frequency measurement' ><[email protected]> >Sent: Tuesday, March 4, 2014 12:07 PM >Subject: Re: [time-nuts] Another "atomic" clock question > > >Hanging bridge? What is it; where is it found; and how does it form? > >My guess is that a Google or Wikipedia search is going to come up with >something named Golden Gate or maybe a musical term. > >Tom Holmes, N8ZM > > _______________________________________________ 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.
