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
On 2/23/2017 10:20 AM, Dave Mueller wrote:
Hi to the group.
I've searched the net (including the archives here) with no luck, so I
figured I'd join and ask my question.
I put down a radial field large enough to support a 160 meter inverted L.
Currently, I have an 80 meter element that I drop and add a segment to for
160 M coverage a few times a year. I'd like to find a way to use a single
antenna on both bands. I anticipate an amp in my future, so I'd like to
avoid using a tuner if possible (especially since a quarter wave on 160
would be a high impedance end fed half wave on 80).
I came across a few references to Yardley Beers' (W0JF) article on trap
antennas from an old HR magazine (August 1987). The concept is interesting
but I've read it several times and am having a hard time following his
design procedure, even using his numbers. Ideally, I'd like to put it into
a spreadsheet so I can make the iterative process faster, and easier to
modify.
A few mail list archives have referenced some DOS software by a G4 ham,
which I downloaded and ran. I couldn't get it to provide a valid solution
with anything approaching a quarter wave of wire on 160 M.
So has anyone been able to duplicate the design process?
Thanks
Dave AA3EE
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