[time-nuts] Wanted to buy or borrow -- RFTG-m-XO L106A

[Charles S. Osborne]

John,

I have my RFTGm-II-XO (L109) open on the workbench (I'm changing the 15MHz
output to 10 MHz) and tried the sequence you mentioned below. Mine reacts
similarly. However, if you reapply a 10 MHz external source to the "10 MHz
REF In" sma it locks after maybe 15 minutes and XO frequency stabilizes.
Initially the Fault lite is on, then clears, and a minute later the "No GPS"
which was on solid, clears.

Note, if you are using the original 15 MHz output frequency, there is muting
applied when things are not stabilized and fault LED is lit.

My RFTGm-II-Rb (L108) unit isn't working. Haven't had time to continue
troubleshooting it since I moved and changed jobs last year, and am just
getting my home lab back in working shape. The Rb unit draws excess current
and blows an on board fuse. I found a few shorted tantalum chip caps two
years ago when I had it opened up. But apparently that's not all of the
problems. It took collateral damage after a lightning hit took out most GPS
connected receivers like my Z3801A in spite of a surge suppressor.

I was sort of waiting for someone on time-nuts, to answer the question of
whether the Rb is disciplined or just used to extend the holdover time.
Seems like I remember it going thru a sequence where the Rb switched over
and acted as primary for a few hours during initial power up. And once the
GPS-XO stabilized it became the ONLINE unit and the Rb went to STANDBY. But
its been almost five years since all that was working, so my memory of that
sequence could be wrong. It would make sense if the GPS-XO was primary and
the Rb acted during holdover wouldn't it?

Wish someone had a manual (or the RS422 magic decoder software). I've sort
of been patiently waiting and watching for someone on time-nuts to uncover a
copy of the Lucent cellsite documentation or something to explain the LED
bahavior on these units. It's more than just ON and OFF indicators, since
they flash as a third status indication format also.

73,
Charles S.Osborne, K4CSO
Duluth, GA

----- Original Message ----- 
From: "John Ackermann N8UR" <jra at febo.com>
To: "Tom Van Baak" <tvb at leapsecond.com>; "Discussion of precise time and
frequency measurement" <time-nuts at febo.com>
Sent: Saturday, March 15, 2008 3:21 PM
Subject: Re: [time-nuts] Wanted to buy or borrow -- RFTG-m-XO L106A


> I'm not sure what's going on.  I ran my XO/RB pair for 30 days, using
> the "official" interconnect cable with the monitoring software
> indicating no problems.  I took phase data from the RB output via the
> TSC and fed it into Stable32 (by the way, with a 20 second timeout, the
> 30 day TSC data capture worked fine).
>
> The results show a reasonably constant +1.5 microsecond slope over 30
> days, about 6x10e-13 offset.  There's no characteristic cliff in the
> ADEV where the GPS kicks in, but yet the offset is better than I would
> expect from the LPRO running in standalone mode.  Plots are at
> http://www.febo.com/pages/oscillators/rftg/
>
> I then pulled power on the RB unit and instead of going into proper XO
> operation, I got "NO GPS" and "FAULT" on the XO.  In separate
> experiments, pulling the interface cable or the 10 MHz cable result in
> the same faults -- the XO doesn't seem to take over as it should.
>
> And, when I measure the XO output, it is just horrible -- ADEV in the 9s
> from 0.1 second out past 10,000 seconds.
>
> I wonder -- has ANYONE gotten the -XO module to work in GPS-disciplined
> mode???
>
> John
> ----
> Tom Van Baak said the following on 03/15/2008 03:25 PM:
> >> I suspect the XO module in my RFTG setup is defective, so I'd like to
> >> find another one.  It needs to be the "L106A" (not "B") version to mate
> >> with my -RB (L105A) unit.
> >>
> >> Anyone have one they'd like to sell?  Or, failing that, one I could
> >> borrow to test in my system?
> >
> > John,
> >
> > Interesting, my RFTG pair won't lock right either; I'm thinking
> > my XO module has a problem too. Do you think we're making
> > the same mistake or are both of our XO modules faulty?
> >
> > /tvb
> >
> >
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