Casey,

One antenna is on a 10 foot pole on a hill. The line-of-sight dips 3 degrees
to the valley floor below. The second antenna is   about 2 feet above and 15
feet from the edge of a sloping composite shingle roof. Aesthetic issues
with the homeowner prevented a taller pole. I realize this is a sub-optimum
situation but thought if the roof acted as a reflector, the 3 degree
reflected RF would miss the 24 dbi antenna. This thinking is irrelevant if
the composite shingle scatters the incident RF energy.

The puzzling part is that the link degrades from solid to no connection in
hot weather.

Grasping for theories, I have stretched so far as to postulate that trees in
the Fresnel zone have a higher water content when actively photosynthesizing
under bright sun and with hot air temperatures. This extra water drops the
signal strength on a marginal link into non-operation.

Any thoughts you might have are appreciated.

Loren Zemenick


-----Original Message-----
From: Casey Halverson [mailto:[EMAIL PROTECTED]
Sent: Tuesday, June 17, 2003 11:21 AM
To: Loren Zemenick; Wireless
Subject: RE: [BAWUG] Why might a 5 mile link degrade during hot weather?


How high are each of your antennas?  Is there an altitude difference between
the two or are they level?



-----Original Message-----
From: Loren Zemenick [mailto:[EMAIL PROTECTED]
Sent: Monday, June 16, 2003 8:17 AM
To: Wireless
Subject: [BAWUG] Why might a 5 mile link degrade during hot weather?


I have a 5 mile 802.11b link that works fine until air
temperatures exceed
around 85 F. Over a period of about an hour, the percentage of
missed pings
grows from zero to 100 percent. Link endpoints are Linksys
WAP11 (ver 2.6)
configured as a point-to-point bridge with 24 Dbi horzontally polorized
antennas.  The WAP11's and power supplies have been cooled with
no effect.
Some trees are in the Frenel zone.  The problem happens weekdays and
weekends. With WAP11's I don't know of a way to measure signal
strength or
quality.

Does anyone have any suggestions as to what might be causing
the outage or
how to troubleshoot the problem?

Regards,
Loren Zemenick

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