[time-nuts] GPS antenna installation problem

Bill Hawkins bill at iaxs.net
Wed Mar 4 21:12:03 UTC 2009


Looks like this subject has ended, so I'll summarize:

Bruce Griffiths said the plastic has 12X the expansion coefficient of
copper, so cold alone shouldn't have pulled the center pin. Now I wonder
if the cold contraction pushed the insulation along the core wire and
then pulled the pin when it warmed up. He also mentioned that some ROHS
connections fail due to thermal cycling, but I used antique solder and
wrench-clamp connectors.

Tom Van Baak asked if the signal degraded or was cut off. I don't look
at it all the time, so my first clue was the Holdover light on the
receiver. GPScon gave me the holdover duration, accurate to 999 hours,
then 1000+.

Stan, W1LE, suggested a captive center pin connector, which I will try
in April or May when the snow goes away. Thanks.

Several people said 20 feet unsupported was too long, but I'm not gonna
fill a 10 foot, 6 inch diameter pipe with foam. I'll get some light
chain and individually tie the cables to the chain, then support the
chain above the point where the cables turn into the 2 foot arms. Metric
conversions are left as an exercise for the reader, as they are for me.

Speaking of conversions, I grew up (since 1938) with movie credits that
mentioned the Gaffer (head electrician). Last year I mentored students
building a robot for a FIRST Robotics competition. The carpet on the
field would be marked with red, black, and white gaffer's tape, which we
got in 2 inch width from a theater supply place. Gaffer's tape is
intended to hold down wires running across a set until the show closes.

Where did Gaffa tape come from?

Thanks to all who contributed.

Bill Hawkins

-----Original Message-----
From: Stan W1LE
Sent: Sunday, March 01, 2009 7:56 PM

a couple of suggestions:

1. Use a captive center pin on the N male connector.
for example, Kings Electronics Inc. N male, model # KN-59-176 for RG-214
coaxial cable, center pin is solder type and captive, will not move
axially. Wrench clamp on the shield.
Kings cage = 91836     
mil spec:  M39012/01-0005

a few bucks each

2. consider adding a foam in place insulation, inside the plastic pipe
to support the coaxial cable.
drill a 1/8" hole every few feet and squirt in the aerosol foam till it
comes out of the hole.
Go for the minimally expanding insulating foam you will find in Home
Depot or Lowes.

Stan, W1LE    Fn41sr    Cape Cod

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