[TowerTalk] Electrical conductivity of crankups for shunt feeding

[Phil Clements]

I think this was an "old wive's tale" started years ago by the owner
of a cheap, flimsy, crank-up!

I have owned and shunt-fed a Tri-Ex LM-470D for years. I have worked
the world on 160 with it and never had any continuity problems.
The only differences with a crank-up are that one must use a flexible
drop wire, and an Omega match, as one has no choice but to attach
the drop wire at the top of one of the tower sections. I used RG-8 cable
for my drop wire; attaching to the shield on each end; with a suitable
spring about one foot long to hold it taught in the wind. My tower was
70 feet tall, with an 18 foot mast with two yagis for good top loading.
The system resonated on 1550 khz, so it was a killer antenna on 160m.
I attached the drop wire at the 34 foot point on the tower. It took about
50 pf for the series cap, and 80 pf for the shunt cap for 1:1 vswr.
I used a choke made up of 35 turns of RG-8 to decouple the RF at
the feed point.

GL!

(((73)))
Phil, K5PC



>
>Having successfully used a shunt fed fixed mast for many years,
>I am contemplating a crankup.
>
>What is the best method of ensuring good electrical continuity
>of the adjoining sections.
>Thanks
>
>John - G3XRJ -
>
>
>
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