Date: Thu, 23 Feb 2017 11:24:05 -0400
From: Herbert Schoenbohm <herbert.schoenbohm@gmail.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Yardley Beers' Symmetrical Antenna
Perhaps the simplest antenna to cover both 160 and 80 is the Inverted L
which is 3/8th wave on 160 and turns out to be 3/4 wave on 80. The feed
point on 160 can be tuned to resonance with a series variable capacitor
about 350 pf and on 80 the capacitor is merely bridged to give you a
reasonable match on 80. Like any inverted "V" it is good to have as
much vertical portion height as possible. If the support is a metal
tower you should try to get some distance of the inverted l from
it....at least 30-50 feet to avoid interaction. The top portion can
slope down to near ground level if that is the best you can do. I would
start with a total wire length of 190 feet and fold back the ends until
you got the best match for 80.
Herb Schoenbohm, KV4FZ
## very slick indeed. The .75 wave on 80m would, or should be resonant, just
like
using a 40m GP on its 3rd harmonic on 15m.
## No big deal to shunt out the 160m series cap, when using 80m., a simple
relay
will suffice, or a small contactor, to increase V breakdown across its series
contacts.
Dunno why I didnt think of that dual 160-80m before, its simple to implement.
A buddy had a 160m inverted L, but ran the vertical wire parallel to the 60 ft
tall
tower, maybe spaced out 3 ft from the tower. Just before top of tower, it
then
went horizontal. He used the well casing for a ground, no radials. Worked
superb
but he was right across the street from the ocean, which makes all the
difference.
Jim VE7RF
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|