Topband: New TX antenna for 80 and 160?

[Renee K6FSB]

Hi Rick-
In regards to copperweld near the ocean,  here in California wire near 
the coast,  my copperweld has not held up too well as the steel rusts 
then fails due to intrusion through any damage to the copper surface. 
solid copper will last much better.
 BTW I understand the utilities use solid copper wire instead of 
copperweld or aluminum for same corrosion reasons.  Someone else may be 
able to verify this info.

I'd feed the dipoles with open wire and use a good matching unit.. 
possibly a remote unit and real open wire feed is also less noticeable. 
( old Johnson Matchbox works for me everywhere except 160, I'm building 
one for 160.  the 2 small holes coming into the shack easy to insulate 
and easy to fix later....it does take some ingenuity to route though)
another possibility is a loop corner fed w/open wire, open at opposing 
corner for 160. makes a low visibility antenna, try modeling and see, my 
235m square loop at 10m high does ok for a stealth antenna on 
75/80/30/40. sometimes all you can do is try some things and see what 
works for u at a particular location.
73, Renée K6FSB

Rick Kiessig wrote:
> Until recently, I was planning to put up an inverted-L as a TX antenna for
> 80 and 160. However, things have changed, and it no longer looks like I'll
> be able to run the radials I would need to have an effective vertical. Now
> I'm leaning toward a low dipole.
>
> My site is highly constrained: it's near the top of a ridge, on a slope,
> facing the ocean (100m above sea level, 300m from the water). The highest
> spot above sea level is the top of my tower: it's only 8.5m above immediate
> ground level (next to the house), although the ground 10m away is 7m lower.
> I can't run more than a wire or two and a coax feed on (not above) the
> ground - an FCP, for example, would be much too large. Due to limitations
> imposed by the city, I can't go higher than 10.5m above ground level.
>
> If I run a wire around three sides of my property in a U shape, hung from
> the tower near (but not at) the feedpoint, I can just hit 80m total length,
> with a 46m long center section and two 17m long end sections. The wire would
> attach to 10m high fiberglass poles near each of the four corners of the
> property.
>
> I recently built a dipole for 40/20/15 using 300 ohm twinlead, which worked
> out very well, so I'm thinking of using a similar approach for this antenna,
> using the full length for 160, and trimming one wire to be resonant on 80.
> I'd like to do whatever I can to maximize bandwidth. If I could cover both
> 80 and 75, for example, that would be great.
>
> Questions:
>
> -- Is a low dipole for 80 and 160 on a sloping site like mine worth the
> effort? I'm interested in DX, not NVIS.
> -- Given my constraints, are there other types of TX antennas I should
> consider?
> -- What's the best wire to use to minimize stretching and to maximize
> bandwidth and efficiency, and that can handle full legal power? I will need
> at least two (maybe three?) wires to cover both bands. Copperweld is strong,
> but I've heard it can be lossy, too. Twinlead has two wires, but it's
> stranded and doesn't feel very strong.
> -- I'm thinking about using Spiderbeam black fiberglass telescopic poles at
> the corners. However, I'm concerned about durability in high winds and
> having enough strength to be able to tension the wires so they don't droop
> terribly. Is there a better choice?
> -- I'm planning to put a common mode choke at the feedpoint and run coax
> from there, as I've done with the other dipole. Any reason to do it
> differently?
>
> 73, Rick ZL2HAM
>
>
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