On Feb 22, 2007, at 7:35 AM, Anthony (N2KI) wrote:
> I think the biggest obstacle to overcome is the antenna. Many,
> including
> myself do not have a 160 antenna. You could load the 80 meter
> dipole but
> NVIS would be your working conditions to some extent. Most already
> are
> aware that to REALLY work DX on 160(or any band for that matter)
> with good
> results is to be at least a quarter wave up. On 160 that's about
> 130 feet.
W8JI has done a number of experiments with full size 1/4 wave
verticals (130 feet) as well as full-size 1/2 wave dipoles at 300 feet.
In Tom's experience, the verticals are equal or more effective than
the dipole for DX in 95+% of the time. There's just a few instances
where the dipoles are more effective, and these are unusual
propagation conditions that occasionally occur around sunrise / sunset.
> That's a big tree. The higher you are the lower the take off angle.
Practically speaking, most hams cannot get a horizontal 160m antenna
high enough to be effective for DX. Tom's 300 foot high dipole is the
exception. That's equivalent to a 20m dipole at 38 feet -- which
would be close to the minimum reasonable height.
For 160m, and for the most part 80m, vertical antennas rule. You do
not need super-high supports to put up a reasonably effective
vertical antenna. Many operators are using inverted-Ls with either
elevated or ground-mounted radials.
I've had reasonable success shunt-feeding my 15m (50 foot) tower
topped with a tribander. This vertical isn't even 1/10 wavelength
tall, although the tribander does offer a bit of top-loading. I had
to build one heck of a matching network to get this to work reliably
on 160m. I worked 370 Qs in the recent ARRL 160m contest, and that
with only 6 hours on. And this was with 100 watts.
If I had more supports (read trees), I would probably go with an
inverted-L.
> It's
> certainly worth a shot, if you have an 80 meter dipole, to see how
> it will
> play out. My guess is you'll have about a 700 to 1000 mile
> radius. I'm in
> for trying.
160m is a really neat band.
Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
-- Wilbur Wright, 1901
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