Topband: Topband Digest, Vol 44, Issue 14

[Herb Schoenbohm]

>Bjorn/ SM0MDG wrote:
>
>to replace my inverted L. My highest support is currently 12 meter
>and I have a limited lot which restricts guying and ground wires but I am
>very close to water in favourable directions....Yesterday I got a message from Cornelius Paul DF4SA announcing his new 18meter fibreglass pole and I immediately started thinking about a higher support for my antenna. Any ideas what to do with a 18 meter/60ft pole like this in my situation?
>  
>
<> Bjorn, if you get such a fiberglass pole my sincere recommendation is 
to forget about inverted L, guy wires and the like.  Rather wrap the 
pole in a even spaced heliax with good copper flat tape or wire of #14 
or better.  If you use the 3M cooper adhesive backed copper tape you 
will need to weatherproof the helical wrap.  Construct a capacity top 
hat for the top of the 12 meter pole with lightweight self supporting 
aluminum spiders...whatever the pole will adequately support.  Place 
this pole over a well configured ground, ground screen, buried or 
elevated radials, and feed with either a bridge T or a simple L network 
against ground.

IMHO you will end up with a highly efficient 160 meter antenna, (it will 
also be a good performer on 80 with proper matching network for that 
frequency.)  The feed point impedence may range, I would guess,  from 
12.5 to 18 ohms depending upon the size of the cap hat and any residual 
ground loss resistence.

If the helical wrap idea is not something you want to do then use the 
pole to support a "T" rather than and "L" as "T"  or three sided top 
guys out 20% wire from the top(before the insulator) tend (even though 
they slope down as guys) to be less cloud warmers then the very popular 
inverted L.

Good Luck,

Herb Schoenbohm, KV4FZ