On Tue, 2007-08-07 at 20:01 -1000, Ken Brown wrote:
> No doubt that Steppir antennas are really nice, and they can be adjusted
> for super low SWR on the line to the antenna, not just between a tuner
> and the rig. That is really neat, and I'd love to have one myself.
> However, it is not necessary to have a Steppir or other remotely tunable
> system, or a multiple resonance antenna (such as one with traps or
> resonant stubs or coils as with Gap or Butternut) in order to have high
> efficiency on several bands. A plain vertical can be tuned (with a tuner
> in the shack) to work efficiently over greater than an octave (like say
> 60, 40, 30 and 20 meters) .
>
> You don't have to spend a lot of money to have an efficient antenna. In
> fact the cheapest simplest homebrew antennas are often more efficient
> than the expensive, ready built (some assembly required) ones that have
> moving parts, coils and other do-dads on them.
>
> N6KB
>
I've had some experience with that multiband simple vertical. First off
one needs to avoid using the 3/4 wave mode unless working only
satellites. At 3/4 wave mode the radiation angle is primarily upward at
45 degrees. Radiation at the horizon where the vertical is prized gets
canceled.
One prefers to go no longer than 5/8 wave without some trap or phase
change loading coil. Then for antenna length (vertical height) down to
somewhere under a quarter wave (efficiency goes down for those short
verticals but they do still radiate) the antenna has a good radiation
pattern with the peak radiation at the horizon.
While simple, the vertical is not all that great on the lower ham bands
for local (or even stateside) contacts. Its low angle radiation pattern
tends to not come down until way out in the Pacific on 40 meters. And so
for a local contact intensive activity like FD it works poorly. For
working DX its great, though there is the downfall of hearing all local
noise sources and some have said "equally poor in all directions," which
can sometimes be applied to QRM as much as QRN.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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