Hi If you mix the RB and GPS down with a mixer you eventually will run into a problem.
As you set them both very close to frequency, the output is a noisy DC signal rather than a sine wave. Since each source can drift either up or down for a short period of time, it can be hard to tell what's going on with a zero crossing detector. It is much better to capture the output voltage with a strip chart or the digital equivalent. Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Raj Sent: Monday, February 08, 2010 10:34 AM To: dan...@verizon.net; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Frequency comparison Hi Dan, Low tech. Yes! IMHO I think its easier for my mind to track an analog indication of Delta-V. I am more analog oriented.. my son OTOH may be able to read a last digit flickering digital display better than me!. I am other wise thinking of a DIY gizmo: Mix two signals in an SBL1 or Eq. Take the phase/DC IF difference out Make a zero crossing detector or similar Timimg the event. Wait for the event in other words! Twiddle the preset again and see what happens. The human mind does a lot more processing than the above with an analog display.. Cheers Raj, vu2zap >Raj wrote: >> >>I was thinking of feeding two 10 Mhz signals to two ports of a SBL-1 or similar and taking the DC >>output at the IF port into an opamp or analog meter. This was visually easier to adjust the drift between two frequencies by just watching the needle move. A stationary needle over a couple of hours would be the best! >> >> >Raj, I did exactly this but with an old chart recorder attached to the mixer IF port. This allows one to leave the room and not have to watch for hours or days. I was able to adjust my -hp- rubidium unit this way against gps to better than one cycle per day. > >Low tech but effective. > >Dan > > >_______________________________________________ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. -- Raj, VU2ZAP Bangalore, India. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.