Re: Power line interference?

From: Peter (prathman_at_comcast.net)
Date: 07/09/04 

Date: Fri, 09 Jul 2004 11:48:08 -0700

Robertwgross wrote:

> Previously, I stated:
>
>>Over time, the center conductor contracts due to heat, and
>>that can pull the connection apart.
>
>
> Actually, most metals expand with heat. What I meant in this case is that the
> sheath expands due to heat, and this makes the center conductor appear to
> contract. The sheath has a lot more metal mass than the center conductor.
>
The amount of metal mass should not be an issue. The amount of
expansion would be controlled by the type of metal and the temperature
change, not by the mass involved. E.g. 10 gauge and 20 gauge copper
wires will lengthen by the same amount if exposed to the same
temperature increase.

However, the coax cable may not have the same metal in the center
conductor as in the sheath and if it's exposed to the sun there could be
a more rapid rise in the sheath temperature compared to the core. Both
of these effects could lead to differential expansion and result in poor
connections.

But I note that in Greschki's installation the GPS receiver seems to be
located very near the antenna:
"GPS antenna (which also houses the GPS board itself, and that is on top
of the building)." So there is no long coax cable connecting the two.

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