Here is what I would do. First, build the proposed antenna, set it up at home
with the coax connected directly to the ladder line at the bottom, the hot and
ground each to one leg. Trim the ladder for lowest SWR on the low end of 40
meters (this should get 20,18,12 and 10 more or less right). Then see if your
internal tuner will tune the antenna as it sits through the coax on 80, 30 and
15 meters. At this point, you will know if you have a viable all band
antenna (unfortunately, most internal tuners are not wide rang e things). If
you are good to here, put down your radials and reconfigure the feedpoint by
shorting the ladder line at the bottom and connect that to the hot side of the
coax and the radials to ground side. Now t ry to tune this arrangement with the
internal tuner. If this doesn't work and you have a 4 to one balun around, you
can put it between the output of the rig and the coax to the antenna and try to
bring the load into the range of the internal tuner with that. It's worth a
try...
If you find a workable arrangement in test, b uild a remote switch box and
"ghost" the 12 volts to key the remo te relay box through the Coax. You will
need a small switch box at the shack end and a relay box at the antenna end,
basically you need a simplified version of the Ameritron RCS-4 (schematic on
Ameritron website) system. This will switch between 4 antennas through the coax
without a control wire , but y ou only need 0 and +12 volts and one relay at
the antenna, so all you need is a two position on-off toggle , the
capacitor/choke/input- output connectors and 12 volt connection at the shack
end and a DPDT relay, choke/capacitor arrangement, one coax connector and a
pair of banana jacks for the ladder line and a DPDT relay at the relay box
end. The relay is set up with one side of the ladder line to each relay
section and the deenergized side hooked up to the coax connector back to the
shack directly and the energized contacts sending both sides of the ladder line
to the center conductor of the connector. Mak e a ground connection on the
relay box to hook your radials to. If you really wanted to get slick, you could
add another relay and a small matching network (a coil and a capacitor) for 160
in the relay box (I assume you will only run 100 watts) if the internal tuner
won't match on 160.
Good luck. What you want to do won't be easy, but could be worth it if you can
make it happen !
Best, Kevin
----- Original Message -----
From: "Mike Smith VE9AA" <ve9aa@nbnet.nb.ca>
To: topband@contesting.com
Sent: Thursday, March 26, 2015 5:12:11 PM
Subject: Re: Topband: ZS6BKW(G5RV) on 160m?
Marsh, Kevin, Jim, everyone
This is great info. Hey, thanks guys,.////As I read these comments, I am now
wondering if there is a magic length of coax, that attaches to the 40’ of 450
ladder line that I could short right in/at the improvised vacation shack end,
or just at the interface to the door/window/outside world, where I will be
allowed to bring the coax in the (for lack of a better term), “cottage”….?
It’s a long story, but I am thinking I am going to be limited to one antenna,
and there may not be any more than one coax, and no going in and out the
building in the wee hours of the morning. A restrictive scenario, but you’ll
just have to trust me.
So, if I could have, let’s say…..10’ of coax in the “shack”, then let’s just
say for example, 40’ feet of coax and then the 40’ of ladder line, could I
short the coax 10’ from the rig in the shack (and even add a coil ?), then if I
wanted to get back on the other bands, simply unshort the 10’ run and put
everything as normal? My goal would be to work some W1’s/W2’s/VE3’s and
perhaps a G/EA, Carib? on 160m just for mults. I’d rather not carry too much
gear with me, so if I could get it in the ballpark and let the Icom’s internal
tuner handle a small mismatch, I’d be OK with that. I might even rethink the 2
gnd radials and tie into the cottage gnd, but whatever works. I’m not clear
yet what the trip hazard ratio will be where I am at.
Hope I was clear. Yes, it’s a strange scenario.hi hi, I even laugh, but I
can’t really tell the whole story. One coax, one antenna-ZS6BKW, no going
outside at night, no external remote tuners …all bands 10-160. Hmmmmm.
If I had more flexibility, I’d string up an inverted L off my proposed 35’
fiberglass mast and run a 2nd coax, but for this particular place, I am
constricted.
I can build and test this before I leave, but I still have to find bare ground
first. We still have many FEET of snow everywhere. Spring has not really
sprung yet.
Mike VE9AA
Mike, Coreen & Corey
Keswick Ridge, NB
From: kolson@rcn.com [mailto:kolson@rcn.com]
Sent: March 26, 2015 2:33 AM
To: Mike Smith VE9AA
Cc: topband@contesting.com
Subject: Re: Topband: ZS6BKW(G5RV) on 160m?
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 too 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
_____
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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