[time-nuts] EFOS2 Maser acting up :(

Dana Whitlow k8yumdoober at gmail.com
Mon Aug 13 20:54:31 EDT 2018


Corby,

What's the H flow rate control doing when the IF level goes down, or
increases, depending?

Prior to retirement, I was the "Keeper of The Clock" at my job, which
entailed riding herd on
our Symmetricom H-Maser (among other things).  At one point about five
years ago, the
IF amplitude began oscillating up and down a few percent, with a period of
around 11 days.
This behavior commenced rather abruptly.  Nothing that was visibly
disruptive to the usefulness
of the system, but definitely worrisome.  The folks at Symmetricom had no
idea what might be
going on, and all they could suggest was "watchful waiting".  I was still
waiting watchfully
when I retired some four years later.  This maser regulates the IF
amplitude via a feedback
loop which adjusts the H flow rate by adjusting power to a heater on a Pd
disk "filter" in the
H path.  I suspect that something has gone wrong in that feedback loop,
such as a capacitor
failure spoiling the loop dynamics, but could not justify shutting down the
system while I
troubleshot the problem.  So I just kept management apprised of the
situation, as well as the
guy who replaced me when I retired.

But if you have a log of internal goings on, as I did, it might well be
informative to study how
other internal parameters varied when your IF amplitude hiccups occurred.

Dana


On Mon, Aug 13, 2018 at 4:56 PM, Tom Van Baak <tvb at leapsecond.com> wrote:

> Corby,
>
> Nice detective work. Keep us posted. I had a case some years ago where my
> IF level was sputtering around. It turned out to be the dissociator. It was
> a pretty easy fix after a fax / email or two from Russia.
>
> If you suspect the L.O. you can always free-run it for a week and see if
> similar symptoms occur. That would eliminate 99% of the complexity of the
> maser as the source of the problem.
>
> /tvb
>
> ----- Original Message -----
> From: <cdelect at juno.com>
> To: <time-nuts at lists.febo.com>
> Sent: Monday, August 13, 2018 1:07 PM
> Subject: [time-nuts] EFOS2 Maser acting up :(
>
>
> > Hi,
> >
> > The EFOS2 Maser is having an "issue", the I.F.level is intermittently
> > fluctuating and sometimes drops all the way to zero. I've always wanted
> > to see the "raw" output from the cavity so now was my chance! Installed
> > two SMA cables  bringing the output of the circulator and the input to
> > the LNA out to where I can get at them. Managed to catch it at zero and
> > hooked a Spec-A to the output of the circulator. Hooray, The Maser cavity
> > output is good, so the problem lies downstream. Installed a directional
> > coupler between the two lines looking back into the LNA. Can see a
> > healthy 1440 Mhz L.O. leakage and logged a reference level. Now just
> > waiting for it to drop again and see if it's the L.O. If not I'll have to
> > dive in again and move my monitor SMAs to look at the 19.6...Mhz I.F.
> > signal. Pix shows the cavity signal on the spec-A.
> >
> > Cheers,
> >
> > Corby
>
>
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