[time-nuts] FTS4060 Continuing Saga

[Brooke Clarke]

Hi:

The antenna is on  a mast about 6 feet above a chimney top.  There are a 
number of surrounding 100 foot trees and this caused a lot of jitter 
last year due to multipath.  I fixed that by changing the elevation mast 
to 50 degrees and that's where it is now.  Changing the elevation mask 
to 70 degrees still shows 400 ns of jitter for a 10 second average.  I 
doubt that any trees are in that cone.

I'm in the  zero-degree timing mode and have a surveyed antenna location 
and so don't see Lat-Lon-Alt type outputs.

For some averages of 10 seconds the jitter is in the 9 ns range but for 
others are in the 300 ns area.  Turning Tropo Corrections off seems to 
lower the jitter.

Thanks,

Brooke Clarke

Rob Kimberley wrote:

>Brooke,
>
>GPS is affected by heavy rain. Signal will be attenuated, and some at low
>elevations may be blocked. Snow is even a worse culprit especially if it
>settles on the antenna.
>
>Do you have antenna mounted in the clear or do you have any partial
>obscuration from buildings or trees (especially wet ones!)?
>
>Best
>
>Rob Kimberley 
>
>-----Original Message-----
>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
>Behalf Of Brooke Clarke
>Sent: 05 March 2006 20:03
>To: Discussion of precise time and frequency measurement
>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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