Mike, this is exactly the antenna I use here at the home QTH. Mine is set up as
a 92 ft flattop and 42 ft feeder , one end at 50 ft the other at 25 ft (that's
what I had to work with). I have a switching box at the bottom that has three
modes:
a)the ladderline is connected directly to the coax running back from the box to
the shack (with a bit of trimming this gives you tunerless operation on
40,20,18,12 and 10 meters.
b)the ladderline is "passed through" to an extention random piece of ladderline
to a tuner at the shack for 80,30 and 15 meters
c)the feeder is shorted and fed to a coax connector to a dedicated external
tuning unit for 160, then back into another connector where it goes back to the
shack through the same piece of coax as the a) arrangement. I have out 30
radials, I know you can't do as many but one does what one can.
This arrangement is one of the best modest all band antennas I have used, and
it does fairly well on 160, I have worked over 100 countries with this, not
awesome, but not to o bad for a small station with a so-so operator. I use a
K9AY for RX here. Just for a dumb comparison, it greatly outperforms a
butternut (not that hard to do, LOL).
I modeled this with a simple antenna modeling program (that I barely knew how
to use) and the matching network it came up with got me in the ballpark. I wish
I remember what figures I got...
Best, Kevin K3OX
----- Original Message -----
From: "Mike Smith VE9AA" <ve9aa@nbnet.nb.ca>
To: topband@contesting.com
Sent: Wednesday, March 25, 2015 8:57:18 PM
Subject: Topband: ZS6BKW(G5RV) on 160m?
I might have a chance to operate from a portable location this summer for a
contest or two but at the location they have no antennas, nor is there room
for any huge vertical, inverted L, guys ropes etc. etc. and no permission to
climb roofs, chimneys, or put a bolt in the building, nor touch the trees.
All very restrictive.
I might be able to erect a 35' freestanding fiberglass mast with a ZS6BKW.
Maybe. The ZS6BKW is basically a 94' dipole with a 40' downlead of 450ohm
ladeer line..which will be sloped slightly, as I don't see a way to get the
peak above 35'
Suffice to say, the best I MIGHT be able to do is sneak in this low
ZS6BKW(G5RV) as an inv. vee to run 10m-80m but I am looking for a way to
ALSO be on 160m to make a few dozen contacts in a contest or two.
I am thinking the peak of the ZS6BKW (G5RV like antenna) would be at max
35'.
For 160m, could I short the 2 leads of the 450ohm ladder line together where
they meet the coax run and sneak out 2 x 65' (bent) ground radials and
attach them to the braid side of the coax?
(maybe I'll even make up a switchbox so I don't have to be running around in
the dark a few times a night reconfiguring bare wires in an unfamiliar
location.)
I've read 3830 contest reports where folks have done this type of thing, but
of all the antennas I have ever had (many!_) I have never EVER tried this
shorting of the ladder line or coax and feeding what is a G5RV as a T-Top
vertical.
with a couple of radials.
I am not sure how a 40' tall vertical with 94' of toploading, models in NEC,
but it seems like it might be close-ish(?) to resonating on 160m. (will I be
in the ballpark?) What kind of matching will I need if any?
I could maybe even add more coax or ladder line to the "vertical" section
when on 160m, however it will also have to be sloped/bent and on or very
near the ground (probably not good, eh?)
I'll be using a modern transceiver with internal ATU.
I am not looking to run pileups on 160m.(where I am going is not rare, just
a nice summer place)..I just want to pick up a few 160m mults in a contest
or two.
Ideas? Remember, I am very restricted. Gotta have the ZS6BKW for my
antenna.and I may not be permitted to have more than 1 coax run out to the
antenna. I doubt adding a couple extra 65' legs is possible either. (no
square footage for that.
Thanks
Mike VE9AA
Mike, Coreen & Corey
Keswick Ridge, NB
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