|[AMRadio] Re: AMRadio Digest, Vol 46, Issue 24|
k4kyv at charter.net
Tue Nov 13 15:20:04 EST 2007
> I wont even run open wire line.
> All my old rigs (even the PP 211's) will be running from balanced PP
> thru 12:1 powdered iron baluns into coax and filters. I wont even run open
> wire line. I also run 12:1 baluns/ununs on the receivers (2.5V HRO,
> NC-240D, SX-9, SX-28, HQ-129X, etc) from the coax feedlines and patch
> it makes a big improvement.
In all my years as a ham I have never used a balun or coax feed to a dipole.
Always used open wire line with a link-coupled tuner. That gives far better
harmonic suppression than feeding through a balun directly to coax, which
offers no selectivity whatever between transmitter and antenna. Besides,
the efficiency of baluns sucks, unless they are looking into a purely
resistive, nonreactive load at the rated impedance. Many of the modern
commercial tuners use an unbalanced T network into a balun for open wire
balanced feeders. Bad design, those things are notorious for running hot,
since a balun was never intended to work into random, highly reactive
The thing I like best about open wire line with a tuner is that one dipole
will work from one end of the band to the other with equally good
performance, and you can work multiple bands with one dipole. I don't like
the idea of nest of dipoles all over the place, to interact with each other
and tangle up in heavy windstorms, not to say how cluttered it looks.
In the past I have run single wire antennas directly to the transmitter,
without using any kind of measuring equipment at all other than trial and
error, and watching how the transmitter loads up. You can estimate pretty
well what kind of impedance the end of the wire should have, if you know its
length and know the frequency you are operating it on. Of course a
thermocouple rf ammeter is very useful. Another good rf indicator is a neon
But attaching the single wire to the tank circuit without any kind of tuner
is asking for a pink slip for harmonics.
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