[CRTech] Christian Radio Tech [MSG 05808]
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If there is no major cost difference in plan A or plan B, I'd stick with the
plan that has been already proven. Who really knows what kind of headaches
are going to be introduced by an increase in TPO and by using that long of a
run of heliax?


-----Original Message-----
From: Michael Barnes [mailto:mbarnes@hcjb.org]
Sent: Thursday, November 20, 2003 11:56 AM
To: Crtech (E-mail)
Subject: [CRTech] Feedline thoughts

We have a 1200 foot tower for our flagship station.  When it was put up,
about 1000 feet of 75 ohm 6 inch rigid feedline was donated.  There are
matching transformers at each end to bring it back to 50 ohms.  At about 970
feet on the tower, the 6 inch rigid line reduces to 3 inch heliax, which
goes the remaining 150 feet to the feed point of the main antenna.

What we were never told, hence did not do, was to replace the "wrist bands"
at each joint about every 8 to 10 years.  Now that we have discovered this,
we need to replace all the inners of the rigid line, an expensive
proposition.  We have received one suggestion to replace the 6 inch rigid
line with a continuous run of 5 inch heliax to the top of the tower, and a
40 foot 3 inch jumper to the feed point of the antenna on the monopole at
the top.  To save money on the removal of the six inch line, it was proposed
to take up a saw and cut it into "manageable" lengths of 5-6 feet, rendering
it total scrap.

The project cost for replacing the inners compared to removing and replacing
the rigid for heliax are probably very close.  The use of the heliax will
require increased TPO, hence increased power an maintenance costs.
Supposedly, this will be offset by eliminating the need to replace the wrist
bands every 8 years.

Any ideas and opinions are appreciated.  I don't have much experience in
this area, but I personally thing we would be better off staying with the
rigid line.


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