If youre stuck with on ground radials figure you wont have room for full
size. In that case see if 50'x 2' rolls of galvanized chicken wire is
available locally. Put out 4 rolls as spokes and wire together at the far
ends and at the antenna base. Also solder the points where they start to
overlap and several more places. The idea is to create an as complete ground
screen as you have time for. If there is close salt water run some bare
copper wire into it from the screen ends; lead fishing sinkers work well to
keep them in place.
Carl
KM1H
----- Original Message -----
From: "bills stuff" <billsstuff@gotsky.com>
To: <topband@contesting.com>
Sent: Friday, August 03, 2012 3:44 PM
Subject: Topband: ITINERANT 160 M ANTENNA - Response Summary
So gently getting back to the topic of the original post which was:
Getting thoughts on relatively simple and relatively inexpensive
portable 160 m antenna, potentially deployable by one person, that
allows for flexibility and somewhat predictable tuning for use on modest
Dxpeds or rare location indigenous ops.
Strawman proposal was for Inv L 50’(or more) alum mast with elevated
radials all tuned with “hairpin” shunt coil – plus a request for
suggestions and potential actual physical assistance with
testing/assembly/distribution.
Principal thoughts to date by TB types posted and direct:
1. More top wires than just one
– doable with minimum additions provided the site has space. Should
improve performance somewhat, requires top wire supports in other
directions (which may only be a minor issue) and some more wire.
2. Mast higher than 50’
- I believe at 55’ (~17 m) it is still quite possible to hoist it up
(maybe not walk up but a rope attached 1/3+ of the way up)
3. Use 18 m fiberglass telescope instead of alum.
- Doable and can be walked up they say, but nearly twice as heavy as
alum, more expensive and bending at top reduces effective height a bit.
But still if you’ve got one . . .
4. Ground radials instead of elevated.
- Could be good for some locations but requires 20+ m radius circle
thick with wires. The innkeeper might not be pleased and also space may
not be available unless you go the tent/generator route. I suppose the
antenna product could be in two flavors, ground and elevated, with
possible different tuning of the top wire.
5. Go to a site that has nicely spaced high palm trees (on the good
propagation side of course) and then . . .
- I welcome volunteer advanced palm tree scouts. Yet perhaps not all (or
even most) interesting 160 m entities have palm trees.
- Yet the point is well taken that a good site with advanced planning
(Google Earth/eyeballs) is important (when possible). This matter has
been looked at for KH8 but I am looking at broader uses as well.
6. Matching not worth the effort with modern ATUs
- Yes but I would not think of trying a semi-serious 160 m effort with
low power (or difficult to match antenna), and the high power matching
units have $, size and weight issues. The current plan has the charm of
a simple, flexible matching coil even at the expense of tuning by
fiddling with top wire and/or elevated radial lengths
7. Receive antenna use
- I purposely did not mention this just to see if it would be seen as an
oversight among TBers. My only personal experience is I don’t have one
and there have been a significant number of high end 160 stations (who
surely have Rx ants) I could hear but could not hear me (my ant is a bit
better than the one proposed here and with 500 w). Of course, his story
may not hold up for a rare-ish DX station.
Anything else?
Bill N6MW
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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