[TowerTalk] INSULATED MAST

[Peter Sundberg]

As people already pointed out, mounting the antenna on an insulated mast
will make no difference unless the coax is run out the back of the antenna
in some way.

I have a moonbounce array for 2 mtrs consisting of 6 yagis with horizontal
and vertical elements mounted on a metal H-frame. Deterioration in the
vertical polarization (elements in the same plane as the H-frame) is about
-1db in comparison to the horizontal plane. Vertical pattern is quite ok so
you can use the antenna this way for sure but it is like giving up a bit of
boomlength that you bought in the first place. In my case I wanted to make
up for the -20db lost from Faraday rotation if polarity is shifted 90 deg
so I am a happy little vegemite despite the fact I loose 1 db when I use
the vertical elements.

A much better approach in your case is to have two antennas bayed with
elements vertical on a horizontal metal mast. They can be considerably
shorter as the stacking gain will put you back in the same region as the
single 8 el M2.

Back supporting the 8 el will put a lot of stress on the mount so it is not
a good idea.

Anyhow, you can put it up on a metal mast and use it, but there will not be
all the db's you paid for in the antenna. I will not be a disaster though
so my suggestion is to try it.

73/Peter SM2CEW
www.qsl.net/sm2cew


At 05:24 2001-06-12 , Steve wrote:
>I recently bought an M2 eight element fm 2 meter beam  to install at the top
>of my mast on my tower.  Where do I purchase an insulated mast section for
>the 2 meter beam that I can connect to my 2 inch steel mast at the top of
>the tower?  I don't remember reading in the m2 literature  that I needed an
>insulated mast though.  But, I don't want to affect the pattern.
>Steve K7AWB
>
>
>
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List Sponsor: Are you thinking about installing a tower this summer? Call us
for information on our fabulous Trylon Titan self-supporting towers - up to
96-feet for less than $2000! at 888-833-3104 <A HREF="http://www.ChampionRadio.com">
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