Topband: Inverted L

[Bill Tippett]

---------- Forwarded message ----------
From: "George Guerin" <gmguerin at voyager.net>
Date: Wed, 06 Feb 2008 08:12:27 -0500
Subject: Re: Topband: Inverted L
Ron, 4S7RO wrote:

 > Any recommendations re adding 80m to an existing 160m inverted L?
Would it be better to:
 >
 > 1) insert a coax trap
 > 2) Tue the antenna at the base (LC network)?
 >
 > My concerns are if the coax trap will decrease 160m performance? If
I impedance match it at the base, it will be a 1/4 on 160 and 1/2 wave
on 80m. The problem there being 1/2 wave verticals usually are
asociated with line radiation problems.
 >
 > 73 de Ron, 4S7RO
 >
 Ron et. al.:

 My two cents worth:

 I have very successfully used a 160 inverted-L with an 80 meter trap
in line. It does give about 16 feet or 5 meters of inductive loading,
so the overall length of the wire is shortened to get 160 meter
resonance.

 I would prefer to use an L-C trap of discrete components. An inductor
of about 10 uHy and capacitors totalling about 200 pfd will work fine.
I would suggest 2 to 4 caps or more in parallel to distribute the
current. Minimum voltage rating 5 KV.

 Coaxial traps do heat up and make some loss. They do work but are not
as efficient as L-C traps. If you need a design for a coaxial trap
from RG8X, e-mail me next week.

 73 & GL

 George PJ4/K8GG on Bonaire for 2 more days ;-))