[TowerTalk] 80m 1/4wave vertical construction

[tongaloa]

Can't help on the tubing size but am also working on a 1/4 wave vertical 
for 80 and
plan to make it a little short and put a 20m trap in the middle for 2 x 
1/2 waves
in phase on 20 as a bonus to the 80. Trimming feed to odd multiple of 
1/4 waves
on 20 should get a decent match on 20...looking at a piece of fiberglass for
the center. Had not thought about guys yet but will probably telescope 
the glass
section in a few extra inches and run some 3/16" eye screws into it.

Want to compare with the 80m, rectangular, vertically polarized, loop. 
3/8 wave
top and bottom and 1/8 wave verticals.

http://www.ee.surrey.ac.uk/Personal/D.Jefferies/slotnotch.html
talks a little about this sort of antenna as related to a slot antenna
but I've not been able to find any analysis of it.

-Bob


Dave N0RQ wrote:

>I am hoping to build an 80 meter 1/4 wave vertical, but have several practical questions.
>
>Size of aluminum tubing?  I don't want to waste $ and buy too big, but obviously
>don't want it too small either.  http://www.texastowers.com/aluminum.htm
>shows what TT sells (and thankfully they are local to me).  I plan to get the 12'
>lengths (unless that is a bad idea for some reason).  Do I start with 1.75" and step
>down ending up with 1.25" on top?  Bigger/smaller?
>
>What about a guesstimate on the length, using tubing like this?  If a wire dipole leg
>would be 61.25' (468 / 3.82MHz / 2), what would be a good starting length for tubing?
>
>Also need an idea on making some sort of attachment point a little over halfway up
>to attach some dacron "guys" for support.  Simple smallish eye-bolts?
>Should I be concerned about dacron getting wet and affecting SWR/performance?
>
>And what is the best way to attach the bottom of the antenna to a 4x4 post, 
>maintaining insulating properties from the post but yet very strong.  Perhaps
>grey PVC over the aluminum and some sort of bracket?  I'm having problems
>visualizing it...
>
>Dave N0RQ
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