Posted by
N2EY on
Sep 28, 2007; 3:08pm
URL: http://elecraft.85.s1.nabble.com/Best-band-for-low-cost-DXing-tp453878p453897.html
-----Original Message-----
From: Darwin, Keith <
[hidden email]>
> DX on a shoe string
Depends on how big the shoes are. What is a minor expense for one person
is a major expense for others. Same for antenna space.
>- 40 meters. A vert of 1/4 to 3/8 wave makes you very competitive on
>this band.
*IF* it's a good one, with a good ground/counterpoise/radial system, and
in the clear. If the RF has to go through trees, buildings and other
absorbers
to get to the sky, you may find a dipole is better.
> A dipole at 1/2 wave high is tough to do.
Depends on your situation (trees, etc.) What do you have?
>A Yagi is even
>tougher. The tall vertical is relatively easy and cheap while
providing
>a better low angle signal than a low horizontal antenna.
>- 30 meters. Again. 3/8 vertical. The power limit on 30 makes for a
>more level playing field.
No DX contests either.
>- 15 meters. Antenna sizes and heights are manageable. Here a
>mono-band yagi on a 25' pole will work well at a moderate cost.
But at this point in the cycle, 15 is at best undependable. And
what you describe involves pole, rotator, etc.
>Those are my thoughts. What are yours?
1) Why ignore 20 meters? Sure, the Big Boys will overpower you
there, but it's where the DX is.
2) What resources do you have? Large open space (rooftop is ideal)
for a vertical with radials? Trees/tall house for a dipole?
3) You seem to favor a vertical. If you can put one up with a good
ground/counterpoise/radial system, and in the clear, that may be
the way to go *if* a high dipole (50 feet is plenty) isn't possible.
The problem I see with most manufactured verticals is that they're
expensive and have multiple traps.
What I'd suggest is a low-resistance (tubing, aluminum downspout,
multiple copper wires) vertical about 28-30 feet high - whatever
works out to be about 5/8 wave on 15 meters. With as extensive
a ground system as possible. A remote-controlled L network matcher
at the base permits tuning the antenna to resonance/low SWR on
any band from 40 to 15 meters. If 15 isn't a priority or you get a
Yagi for the band, go for more height to increase performance on
the lower bands. At around 42 feet, you'd have a 5/8 wave on 20
and more than a quarter wave on 40.
While manufactured remote-control matchers exist, you can make your
own and save $$. The trick is that the matcher only needs to match
your particular antenna on the bands you use. Such a matcher could
consist of a single tapped air inductor (large and homebrew, to save
money and be low loss) with one tap for each band,
taps being selected by relays. One variable capacitor turned by an
old electric-screwdriver motor does the rest. If you want to cover
4 bands (say, 40/30/20/15), you only need 3 relays and 4 control
wires plus ground. (There are tricks to reduce this even more but
for simplicity I'm going basic). Sure you have to find the taps by
experiment, but you only have to do it once.
Just my ideas. IMHO. YMMV. LSMFT
73 de Jim, N2EY
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