[TowerTalk] Yardley Beers' Symmetrical Antenna

[Herbert Schoenbohm]

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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