[Top] [All Lists]

Re: [TowerTalk] Inverted L for 160 meters

Subject: Re: [TowerTalk] Inverted L for 160 meters
From: VR2BrettGraham <>
Date: Fri, 19 Oct 2007 03:58:33 +0000
List-post: <>
N4UM explained to Tom:

>The 165-175 foot length (longer than a quarter wave) raises the radiation
>resistance of the antenna to somewhere close to 50 ohms but, at the same
>time increases the inductive reactance.  The capacitor is used to cancel the
>inductive reactance when the total length goes beyond a quarter wavelength.
>I use the same technique by making my "quarter wave verticals" longer than a
>quarter wave to bring their radiation resistance up to 50 ohms and then I
>tune out the additional inductive reactance by using series capacitance.  I
>live in a salt water environment and do not like using  expensive variable
>capacitors that are exposed to the elements.  I use pieces of coax as a
>simple inexpensive substitute for variable capacitors.  RG-8 runs about 30
>pf per foot.  I "tune" the coax capacitor with wire cutters and seal the
>exposed end with epoxy when I get the length right.  The trick is not to
>snip too much off at one time!

Presumably this is with elevated radials?  I thought once close enough
to ground, radial length determined performance of return currents
(significantly reduced beyond where the radial ends) & not resonance.

73, VR2BrettGraham.


TowerTalk mailing list

<Prev in Thread] Current Thread [Next in Thread>