Stan,
A few days before a 1975 CW DX contest, I stacked a 3 element 20 meter Yagi
about 8 feet over an existing full size 3 element 40 meter Yagi on a 140 foot
tower. I checked out the 20 meter Yagi on the air, and it worked great. I
foolishly did not check the 40 meter Yagi before the contest, thinking "nothing
could go wrong." huh...
As usual, I started the DX contest on the low end of 40 meter CW expecting
120++ rates. The band was in great condition, but I couldn't get a decent run
going with my 40M Yagi... I started S&P and was consistently getting beaten
in routine pileups. Then I noticed that the strength of the European signals
didn't change when I pointed the 40M Yagi south... Shortly afterwards I
climbed the 140 foot tower in the middle of the night, with a flashlight in
hand,thinking that something obvious would be wrong but everything looked
perfect.
I mulled this over while operating all night and decided that the all metal
construction of the 20M Yagi must have top loaded the 8 foot mast to create a
top loaded 40M vertical connected to the all-metal 40M Yagi. During some
slower periods on Saturday, I constructed an insulated plate to replace the
boom-to-mast plate on the 20M Yagi. In mid-afternoon, I climbed the tower
again, and replaced the aluminum 20M boom-to-mast plate with the insulated
plate.
Voila... the 40M Yagi worked great and it was off to the races to recover
from the disastrous first night. That was the first W3LPL single op (yes... I
did that all thru the 70s)first place finish in the ARRL DX Contest.
Since then, I've always mounted elements using type LE phenolic plates. This
helps to avoid "surprise" effects as described above. While you could also
insulate booms from masts, I've never done that except for that one "emergency"
repair described above.
73!
Frank
W3LPL
---- Original message ----
>Date: Tue, 5 Sep 2006 9:43:34 -0500
>From: Stan Stockton <k5go@cox.net>
>Subject: [TowerTalk] Garolite
>To: donovanf@starpower.net
>Cc: towertalk@contesting.com
>
>Frank,
>
>I have a high quality, solid, molded fiberglass rod that I will use in the
>center to split the elements. One of the questions had to do with LE material
>which I had seen that you had used. According to the specs listed for it on
>McMaster Carr, the tensile strength is about 1/4 that of G10 or G11 which is
>even stronger than G10. Duffy said that he uses G10 instead of LE.
>
>The next question has to do with insulating all the elements. I could not
>find a previous posting from several years ago where I believe you stated some
>positives relating to interference issues, etc. from having insulated all the
>elements. If you could let me know what all those positives were I would
>appreciate it. Not sure whether you try to insulate the boom from the mast or
>not?
>
>Thanks...Stan
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