[TowerTalk] Multi-band antenna projects

[Dave_K9NX]

At 12:22 PM 8/29/98 -0400, gbay wrote: 
>
> <snip>
>     1.  I've got enough space to make an inverted L by shorting out the Gap
> and running a wire from its top to the peak of my roof which is probably
> about 40 feet high.  The total length including the vertical would be about
> 130 feet.  (The Gap is about 10 feet down off the side of a hill.  I suspect
> that this might make a fairly decent 160 antenna if I put in a good radial
> system.  However, I lose the multi-band feature.  Perhaps an 80 meter
trap in
> the wire?  That might get me two bands working better than the Gap
> alone...what do you think?


k9NX: I have an all wire version of this just as you describe. The trap is
constructed using using a 20KV 100pf (fixed ) vaccumn capacitor that I
boght at
Dayton this year for $3 and enough #10 wire wound on 3" PVC pipe form to
resoanate at 3.525. works fine. Bury lots of radials. I'm not sure the Gap
would support the trap without some kind of back guying near the top. The
ffect
of the trap will be to lower tthe resonant frequency on 160M so you will nedd
less than 130' overall.


>
> 2.  Another scenario is to try to load my tower.  It is a TX-472MDP motor
> drive and I keep it retracted most of the time to keep the neighbors happy. 
> The shunt feed would have to go up and down with the tower so I imagine that
> SWR repeatability would be a problem.  Also, there would be no way to bond
> sections together electrically.  Anyone ever try this??



K9NX: Use coax for shunt feed its more flexible and less prone to kinking, but
if you go up and down a lot this could become tricky. Should work better than
the 40' GAP/Inv L though.

>
>  
> 3. Where does one get variable and fixed capacitors and inductors capable of
> handling 1.5KW for matching networks?



K9NX: Lots of vaccumn variables at hamfests. Also a couple of the surplus
places carry em.

Dave 
k9nx 

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