[Towertalk] 40 meter boom, 80 meter dipole?

[n4kg@juno.com]

Sounds like an ideal design for 80 / 40 Paul.

The majority of the boom loading comes from the end elements.
The best way to support the matching arm is under the boom.
You can feed at any point below the 50 ohm point (wherever
that might be), using a Omega Match (shunt C to boom followed
by a series C with the arm to cancel inductive reactanace).  I
expect you would get the best bandwidth with a matching arm
out to the end of the element.  You could make TWO matching
arms, one for CW and the other for SSB.

I will be very interested in your results.  Sounds like a GREAT
article for publication in QST or other widely distributed outlet.

73 / GL,  Tom  N4KG

On Tue, 21 May 2002 Paul Young <k1xm@underwater.org> writes:
> I have a three element 40 meter beam.  I'm thinking about
> matching the boom as an 80 meter short dipole.
> 
> The boom length is 48'.  The driven element is insulated but
> the parasitic elements are connected to the boom.  They are
> full size and provide plenty of end loading.  It has a T-bar
> truss which is not insulated but I don't think I would want
> to use it to feed the antenna.
> 
> The problem, of course, is feeding it.  Tilting the antenna
> is difficult, but I figure I can tip it once and install
> some sort of omega rod.  Then I can tune it from the mast.
> The bandwidth may be narrow enough that I'll need to put up
> a relay to switch it to phone.
> 
> Has anyone tried this?  What sort of omega rod will I need?
> Any caveats?
> 
>                            Paul, K1XM
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