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Topband: Fwd: Re: My 160m antenna

Subject: Topband: Fwd: Re: My 160m antenna
From: Charles Bibb <>
Date: Sun, 15 Feb 2009 14:55:33 -0600
List-post: <">>

>At 12:16 PM 2/15/2009, you wrote:
>>I just wonder what would I gain by changing to a full length 1/4 wave wire.


I tried e-mailing you directly, but it bounced.  So, I'm posting to the group.

I used one of these to very good effect for over eight years on a 60 
foot tower with the FP at 55 feet.

The coil inductance is high enough to serve as a trap on 40M and as a 
loading coil on 160M.  The enamel coating on the small-gauge wire 
they use for the coil is subject to degradation due to weather and 
the effects of UV radiation, meaning that the turns will eventually 
short together.  I made my own bigger and better coil to (A) mitigate 
the effects of weather and sunlight, and (B) reduce losses.  If I 
remember correctly, the coil inductance is about 125 
micro-Henries.  My HB coil was made of #12 solid wire, 5" diameter 
and about 13 inches long, 4 TPI, would around 6 grooved plexiglass 
ribs that I painstakingly made myself.  Very labor intensive, and 
very well worth the effort.  That antenna works very well for what it 
is.  It allowed my to get out a good low band signal from a small 100 
x 125 foot lot.

The problem with removing the coil and extending the length of that 
leg is that (A) you will lose 40M , like you already mentioned, and 
(B) with only 50 feet of FP height you will end up with a lot of 
"extra" wire to find a place for.  Folding the extra back on itself 
(a al linear loading) will increase your losses as compared to using 
a better-constructed, higher-Q coil, and laying it all out straight 
will introduce more horizontal radiation, and require a larger 
"footprint".  The twin sloper relies on its vertical polarization to 
put out a good low angle signal for DX work.

I found fabricating a better coil a big advantage, but I can't see 
any real advantage to loosing the coil.

Hope this helps, YMMV

Charles - K5ZK

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