On Tue, 6 Jan 2004 10:34:08 -0700, "Ken Bessler"
wrote:
"Stef" wrote in message
snip
You should try to put up a 130 ft wire dipole instead, with a balun,
good coax and a tuner. Then you can do whatever you please with the
ends of the wire.
snip
I kinda like the idea of
the all bander antenna because 1) it has more wire and 2) it has
a longer ladder line, allowing it to reach my window. That way,
my feedpoint would only be 7 feet from the tuner (less loss in
the rg-58 coax).

Hi Ken,
7 feet is no virtue, and could easily be a problem. The loss of
RG-58 over a span of 10 times as much may seem like a lot, but only
amounts to less than 1dB at the low HF to less than 3dB at the high
end. Let's split the difference and call it 2dB when looking into a
matched condition. THIS is the only reason to have a tuned antenna,
because line losses increase with SWR.

If you run with a simple doublet (whatever stretch of a wire dipole
your supports can hold in the air), it is obvious that the concept of
tuned is a caprice of chance. It pays then to use ladder line where
the losses due to the certain SWR are lower (owing to the larger
conductors only).

Calling an antenna multibanded can be achieved through either building
traps along its length that variously shorten it at high frequencies
and lengthen it at lower frequencies (the interaction of these two
agendas and the proximity of ground can easily drive you crazy) -OR-
it can be achieved with large block letters in the advertising copy.
If you cannot erect the trapped doublet high enough, the results may
be identical to the one bought on the basis of its multi-colored bold
typeface ad - equally lossy.

Hence, draping these "multiband" antennas such that they approach the
ground forces you to employ a tuner to take up the slack. If you have
to use a tuner, you best use ladder line. If you are using ladder
line and a tuner, you don't need tuned antennas. If you don't need
tuned antennas, you don't need to drape the doublet where it
approaches the lossy ground. If you are hoping to erect a multiband
meaning it covers 160, you are describing an air cooled resistor.

You may note the circularity of this, or the chicken and egg problem.
The truth of the matter is that almost any combination of
tuned/untuned antenna, with ladder/coaxial line, into a tuner will
give you fairly good operation. Unless you are sitting at the feed
point 7 feet away. If you park your car in the living room, you would
have the benefit of a Faraday shield to protect you and your equipment
to overcoupling to the fields you are trying to transmit. However, if
you put some distance between you and that point, you obtain a square
law advantage. At 14 feet you and your gear are exposed to one
quarter the output. 28 feet away, and you are down to one sixteenth
the exposure.

Even at this distance, some Hams experience their gear locking up
(foldback even at low power) due to close proximity (this is all
wavelength based, 40M operation with this problem is a classic
complaint in this board). This is due more often than not to poor
choking at the feedpoint, but proximity comes in a close second.

73's
Richard Clark, KB7QHC