Traditionally, the 80 meter dipole example you sited was the typical
improvisation guys used to get on 160. How well it worked depended on how long
and vertical the feedline was and a lot of luck, basically how close to a "T"
top loaded vertical fed against ground it ended up being . But a little
intention could make it work much better.
When I put up my first antenna at this QTH (a 92 ft dipole fed with 42ft of
open wire line aka ZS6BKW antenna), I put a switch box at the base that shorted
the bottom of the feedline and fed it to a matching network to make it an
actual "T" on 160 and put down about 30 random length radials at ground level.
It has worked pretty well for what it is.
In your situation, you don't really have anything approximating the traditional
"T" . So applying intention to your case , since you already have a vertical
with radials, I would say that the easiest good solution would be to put a
loading coil between the antenna end of your feedline choke and the radiator of
your 40 meter vertical and tap it for resonance. You cou ld just physically
switch it in and out to change bands, but ultima tely you will probably want
to work out a way to use relays to remote switch the taps, with no inductor in
series on 40 meters and progressively more on o ther bands (you cou ld add 60
and 80 meters in addition to 160 if you wanted). You would ne ed to either run
a control cable or build an arrangement to inject the switching voltage on your
existing coax. What you would end up with is a base fed vertical, basically a
version of the Butternut vertical system which works reasonably well on 160.
You may want to add a few longer radials to help further on 160.
The low wire would probably be a very poor antenna on 160.
73, K3OX
----- Original Message -----
From: "Joe" <nss@mwt.net>
To: "TopBand" <topband@contesting.com>
Sent: Monday, December 17, 2018 9:31:49 AM
Subject: Topband: 160 Antenna
OK, as users of this band, we all have probably done this at least once
in your radio lifetime.
You want to get on 160, but do not have an actual 160 antenna. So you
connect the largest antenna ya have, usually a 80 meter dipole, but you
just push the connector in just so only the center pin is touching, and
load the whole thing up like a top capacity hat, vertical, or end fed
long wire. Hey it works.
I'm thinking of doing something similar, because a full sized 1/4 wave
elevated vertical for 40 meters, works as well as a cannenna does when
trying to use it on 160.
But I never thought of what might be the best way to do this. The
antenna as stated is a full sized 1/4 wave elevated Vertical, The base
of the vertical is 10 feet above the ground with sloping radials that
act as guy wires also to hold the base in place.
At the base of the antenna right at the feedpoint, is a large multi turn
coax choke. ( Ya know the so many turns on a PVC pipe thing )
The feedline is then ran through the air for about 60 feet to the eve of
the house where it runs along the eve of the house on 2 sides and
finally into the shack. Total length is about 100 feet.
Now I am trying to decide without actually trying to make up connectors
or whatever, what might be the best way to use this on 160.
1- As described above just the center pin, touching. I guess with the
braid floating the braid gets capacitivly coupled to the power and does
the radiating and receiving. YES? NO?
BUT I can see the RF actually also going and using the existing vertical
because of the touching center pin. BUT, the braid signal, I'm assuming
the RF is not getting past the Coax coil and using the radials.
2- Apply power to only the braid? similiar to #1 but backwards. again
no power to the radials probably?, and only cap coupled to the vertical.
3- short the center and shield together and run it that way.
Anyone have any thoughts of the best configuration any thoughts?
Or how would a end fed random wire like 1/4 wave long about 10 feet up
work better?
Joe WB9SBD
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