[time-nuts] FTS4060 Continuing Saga

Tom Van Baak tvb at leapsecond.com
Sun Mar 5 20:53:55 EST 2006


Check for a wet connector or cable at the GPS

Check your SR620 settings. They are lost when
you power cycle, yes? The jitter sounds more like
an input trigger issue than GPS signal & rain issue.

We get rain here all the time... It certainly doesn't
cause the magnitude of what you're seeing.

Did just the jitter change, or are you seeing a new
phase offset and/or a new frequency offset than

Did you have to re-load the zero-D coords into your
GPS receiver? Make a lat/lon typo perhaps?


----- Original Message -----
From: "Brooke Clarke" <brooke at pacific.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Sunday, March 05, 2006 12:02
Subject: [time-nuts] FTS4060 Continuing Saga

> Hi:
> After Tom helped me a month ago to get the trigger level correct for 50
Ohm loaded TTL (1.25 volts), I've been seeing no aging on the FTS4060 s/n
1013 and have been tweaking the C field and all was going well, but today
(heavy rain) the jitter on each 500 second average has jumped up from about
9 ns to more like 300 ns which means you can not believe the readings.  It's
snowing on the nearby mountains and heavy rain here.
> Note that on prior days the daily spread in the Time Interval has been
around 10 ns peak to peak.
> So does GPS suffer with heavy rain?
> I checked TAC32 and the receiver settings are correct.
> Interesting sidelight:
> A couple of days ago there was a brown out the caused the SR620 counter
and the computer to reset, but the FTS4060/S24 (no backup battery) did not
reset (Lock and AC ON green LEDs) and the data shows that there was a
recovery that lasted about 1,500 seconds.  Not sure what was moving.
> Have Fun,
> Brooke Clake

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