Topband: New TX antenna for 80 and 160?

[Tom W8JI]

> 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.

Why not use a dipole and feed it like a "T" on 160 or maybe 160 and 80??

Are they really going to inspect what is buried or laying on the ground, so 
far as a counterpoise??

For what it is worth, a friend of mine lived on a city lot in a densly 
populated area with only about ten feet of back yard depth, and about 130 
feet of length. He was surrounded by parking lots and buildings. I had about 
100 radials with a 1/4 wave tower, and I lived in an area with rich wet 
black sandy loam. From that back yard, he was consistantly within a few dB 
of my signal.

You never have known his end-fed 80 meter Zepp antenna was there.

Harold did so well from a tiny lot it actually caused him social problems. 
Another nasty bitter old cranky man (the type we seem to tolerate up here) 
named Joe was so upset Harold was significantly louder then him, that grumpy 
old Joe would actually curse poor old Harold. It was always quite a show.

> 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.

Anything works. Anyone can work DX with a low horizontal antenna. It doesn't 
exclude DX like a some sort of filter would.

> -- Given my constraints, are there other types of TX antennas I should
> consider?

I'd consider a T antenna out of a dipole, or a bent wire.

> -- What's the best wire to use to minimize stretching and to maximize
> bandwidth and efficiency, and that can handle full legal power?

Any wire can handle full power, but you want **real** copperweld or solid 
hard drawn copper. You can hard draw your own solid copper wire.

Watch out for Ham wires that use very thin copper coating or cladding. There 
is a lot of that, and the stranded copper clad steel sold for Ham use is 
absolute junk. The copper is so thin the RF is down in the steel on low 
bands, and the stuff rusts if scratched or rubbed.  A good copperweld has a 
pretty thick copper overlay, and that generally means it should be at least 
a 16 gauge strand. If you see fine strands or wire the size of a thick 
needle, it will behave like steel on low bands and be subject to rust. That 
doesn't mean it is useless, just not the best.

I have copperweld here on beverages and other antennas, and I can scratch it 
with a knife to clean it and it won't rust. If I even try to solder the Ham 
grade junk, it rusts.

Copperweld is (or was) used in long life outdoor support cables like for 
bridges, so there may be local suppliers to you.

73 Tom