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 <t...@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: <cdel...@juno.com> > To: <time-nuts@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 > > > ------------------------------------------------------------ > -------------------- > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/ > listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.