On Tuesday, August 19, 2014 2:10:01 AM UTC-5, Robert wrote:
I would like to ask for recommendations for specifications of a wire dipole that

will give me the most bang for my portable buck. For example, Using an Icom 703+

at a different location, (friends back yard, local park, etc.) and remembering

this model includes a built in auto-tuner, would I get the most out of a single

band dipole, a dipole that can be tuned for more than a single band, an OCF

design, or loop? I would like to be able to use a single antenna design for as

many of the HF bands it would be capable of used in conjunction with the afore

mentioned auto-tuner? What bands? I'm not especially fussy, but hopefully I can

get away with using it on 40 and 20meters. More up to all the HF bands would be

fantastic, but I'm sure I will be told it wouldn't be practical.



Right now I have 2 40' lengths of stranded 20ga. wire, but that doesn't mean I

can't get other lengths and gauges. So, any ideas? Just keep in mind that this

isn't supposed to be a major production. I'm requesting designs that have worked

for "you" in the past or present, is easy to put up/take down, while taking

little time. Ideally, something I can hook up using adaptors that will allow me

to hook the wire antenna either directly to the radio, or using a short length

of coax, ladder line, etc. between the antenna and radio.



Again, the radio is an Icom 703+ that will be powered by a 12V/10Ah gel cell,

and used in an appropriate SSB mode.



Thanks & 73,

Rob, KB2ZGN

Not sure what you mean by the most bang.. The most efficient, or the
most bands to be worked. ??
If you want the most efficient system for QRP, I'd run a regular
dipole fed with coax for a single band. But you can run more than
one set per run of coax. IE: you can have 40 meter dipole legs, and
20 meter dipole legs run at right angles fed with a single coax feed.
That would be two bands with high efficiency, and the 40 meter legs
will work 15 pretty well if you use the tuner to tweak the match if
needed. You could probably work other bands using the tuner, but
efficiency will suffer a bit. You can use more than two dipoles also,
but might need to tweak the tuning a bit if there is any interaction
due to the legs being close together. If you do see this, it will be
on the higher of the bands used in most all cases.
Two dipoles at right angles have almost zero interaction, and in
practice neither will be aware the other exists.. :|
And instant band change with no tuner diddling required when running
the parallel or fan dipoles.

For all bands with a single dipole, I'd go with the single dipole for
the lowest band to be used, and fed with ladder line/twin lead and a
tuner capable of that.
But you can't run that with the built in tuner in that radio.
It's more of a line flattener, and not suitable for feeding open line,
or really bad mismatches.

So with what you have, I'd run coax fed dipoles if no outboard tuner.
It will be the most efficient system overall, and the dipoles fed
with a balun will have much less balance and common mode issues vs the
OCF antennas. Out portable, you really don't even need a balun if
working light and simple.. It's better to use one, but most times it
will work fine without one. Just skews the pattern a tad, which most
won't even notice. You can also roll a section of the coax into a choke
at the feed point to decouple the line.
On the HF bands, overall you can't beat the efficiency of a coax fed
dipole as far as the overall system. You don't need a tuner, so no tuner
losses, and the coax losses on HF are low for the usual length runs.
Almost all the RF from your rig will be radiated, and with QRP, you sure
don't want to waste much.