[time-nuts] GPS antenna installation problem

Alan Melia alan.melia at btinternet.com
Sun Mar 1 22:57:08 UTC 2009


I am sure it is NOT a good idea to hand heavy cable like RG-8 from the
N-type connector. What will hapen is that the cable will walk out of the
connector and the centre pin will withdraw from the socket. This happens
whilst the outer jacket stretches so there is no indiction there is a
physical problem. This can happen very quickly but does depend on the strain
put on the cable (Amateur Radio field-day experience !!) You should always
loop the cable and take the strain off the connector totally. Take the cable
down and remake it, add strain relief,  and all will probably be well.

Alan G3NYK
----- Original Message -----
From: "Bill Hawkins" <bill at iaxs.net>
To: "'Discussion of precise time and frequency measurement'"
<time-nuts at febo.com>
Sent: Sunday, March 01, 2009 8:05 PM
Subject: [time-nuts] GPS antenna installation problem


> Group,
>
> My GPS time system consists of two Z3801A receivers with two HP cone
> antennas.
> I built a mast from plastic pipe (6" base to 2" arms) that is about 16
> feet tall.
> The antennas are 4 feet apart, each 2' from the center of the mast. The
> mast
> rises from a deck and is fastened 8' up at the roof line. The mast sits
> on a
> 3/4" sheet of high density marine plastic fastened to the deck with
> stainless
> hinges so that the antenna can be folded away from the house and brought
> to the
> deck railing. The mast was put up in 2003.
>
> The antenna cables are each half of a 100' coil of RG-8U. Each cable is
> about
> half in the house and half outdoors. N connectors are soldered to both
> ends, so
> no adapters are used. The cables leave the house through a waterproof
> boat deck
> fitting and travel about 5' under the deck to the mast. There's a
> service loop
> to allow the mast to be lowered, then the cables rise unsupported
> through the
> mast pipe and branch out to the antennas, which support the weight of
> the cables.
>
> Oh, and the location is Minneapolis, MN, USA.
>
> The problem is loss of signal during cold weather. Last winter (07-08) I
> lost
> the signal from one antenna during a cold snap, but it came back a week
> or so
> later when it warmed up outside. This winter, I lost The North antenna
> on Nov
> 22 when the low was 15, and it didn't come back. Then the South antenna
> went
> away on Dec 24 with a -17 low and didn't come back. I'm still running on
> holdover.
>
> I suspect that it's not a good idea to hang 20 feet of RG-8 from an N
> connector
> without some kind of strain relief, but I don't know why that would be a
> cold
> weather effect. Perhaps the center conductor shrinks more than cable and
> its
> braid, and pulls the center pin out. There's definitely an open circuit,
> looking
> at the receiver end of the cable. There's no alarm from the Z3801.
>
> Any thoughts, comments or ideas?
>
> Bill Hawkins
>
>
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