I'll second the interesting part. I have a problem with a 10 GHz brick oscillator LO that I converted to GPS lock. I don't remember the instantaneous frequency jumps (around 200 - 400 HZ at 10 GHz) before I did the GPS lock (although it's possible). Please note that this is NOT any type of GPS phase shift. I built a extremely slow frequency lock circuit that has a loop time in seconds. The jump is instantaneous and I can then see the control voltage slowly change to correct the error. When the frequency jumps back, the control voltage slowly follows. Since this brick has the usual 106.5 MHz crystal (multiplied by 96 to get 10.224 GHz for the LO), I'm seeing at most 400 HZ / 96 shift in the crystal oscillator.
I've wondered if I have a noisy varactor diode. The diode selected was one I had around, selected only because it had a low-ish capacitance value. I haven't gotten around to digging into the problem any farther. Anyone have any more info or ideas? 73, Tom WB6UZZ --- On Thu, 10/18/12, John Miles <[email protected]> wrote: From: John Miles <[email protected]> Subject: Re: [time-nuts] HP 10811 Tuning Diode To: "'Discussion of precise time and frequency measurement'" <[email protected]> Date: Thursday, October 18, 2012, 8:54 PM That's extremely interesting, Adrian. I've never heard of a noisy varactor, but then I've never looked for one, either. It'd be great if some of the problems that have been blamed on jumping crystals were in fact caused by the tuning diode. What steps did you take to rule out the crystal and narrow down the problem to the diode? -- john, KE5FX Miles Design LLC > -----Original Message----- > From: [email protected] [mailto:time-nuts- > [email protected]] On Behalf Of Adrian > Sent: Thursday, October 18, 2012 12:19 PM > To: Discussion of precise time and frequency measurement > Subject: [time-nuts] HP 10811 Tuning Diode > > Hello, > > I found the 10811 in my 8662A to be quite noisy and was able to trace > the problem down to the tuning diode. > Actually, the phase noise started to jump when the oven heated up. As a > quick solution, I replaced it with a SMD type that I had at hands. > > I would appreciate any hint where to find an original diode (even though > I could leave it as is). > > As by the manual, the original is a '0122-0244 DIODE-VVC 100PF 5% > C4/C25-MIN=2 BVR-30V Mfr. 28480' > Mfr. 28480 is listed as HP, but the diode is marked 'M' for Motorola and > '0244' and '312'. > > Adrian > > _______________________________________________ > 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. _______________________________________________ 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. _______________________________________________ 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.
