[time-nuts] HP 10811 Tuning Diode

[Azelio Boriani]

I had a noisy varactor experience too: in my Tek 492 one day I noticed an
increase in the 0 beat noise and the PLL not working. When I replaced the
2.2GHz conversion varactor all was back to normal.

On Fri, Oct 19, 2012 at 6:54 AM, Tom Curlee <tcurlee at sbcglobal.net> wrote:

> 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 <jmiles at pop.net> wrote:
>
> From: John Miles <jmiles at pop.net>
> Subject: Re: [time-nuts] HP 10811 Tuning Diode
> To: "'Discussion of precise time and frequency measurement'" <
> time-nuts at febo.com>
> 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: time-nuts-bounces at febo.com [mailto:time-nuts-
> > bounces at febo.com] 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 -- time-nuts at 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 at 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 at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>