[Elecraft] wire antennas

[David Cutter]

I always advise using a non-resonant length for a multi-band doublet with 
tuner combination.  There's a magic figure: multiples of 44ft, 88ft... that 
Cebik came up with which is a good compromise with impedance matching, ie 
not horrendously high or low X and R.  I notice no-one has mentioned the 
G5RV and its derivatives, yet.

David
G3UNA

----- Original Message ----- 
From: "Mike Morrow" <kk5f at earthlink.net>
To: <elecraft at mailman.qth.net>
Sent: Tuesday, February 20, 2007 11:50 PM
Subject: Re: [Elecraft] wire antennas


> Stuart wrote:
>
>>Even simpler is a 80m dipole fed with balanced line to a tuner for all 
>>band
>>use.  The window line is less costly than coax.  A good quality tuner is
>>less lossy in multiband use than coax/ tuner balun, etc..  Balanced 
>>antennas
>>have fewer problems than off center feeds.  Balanced line to dipole does 
>>not
>>need a balun at the antenna.
>
> That's always seemed the ideal approach to me.  You can go anywhere with 
> it with very low resulting losses, which is also very useful for 
> MARS/CAP/SHARES work on those odd HF military frequencies.
>
> The only real problem seems to be routing the balanced line from the 
> antenna into the shack without it having much interaction with nearby 
> materials.
>
> A second problem is the lack of real balanced-line antenna tuners. 
> Unbalanced tuners with that small output balun are problematic.  I bought 
> an old Johnson Matchbox just because it is one of the few true balanced 
> tuners can can still be found.  I know that MFJ has a couple of non-balun 
> tuners design for balanced line, but I've never investivated their 
> technical details, nor read reports on how well they perform.  Obviously, 
> these would not serve the "gotta swap bands in five seconds" contest 
> crowd, but that's not me.
>
> I never trusted those resistor-terminated folding dipoles.  Every analysis 
> of them that I've ever read over the past 30 years has been basically 
> unfavorable, as one would expect, with performance at best very much below 
> that of a simple dipole.  It is similar to a broad-band antenna design 
> using any length of center-fed non-folded dipole fed with coax, with a 
> hefty 50-ohm resistor across the coax leads at the connection to the 
> dipole.  You'd get good VSWR with that from 1.8 to 30 MHz!  Come to think 
> of it, about 25 years ago some outfit was hawking something just like that 
> to hams at high cost.  Yet, I'm sure you could make some contacts with it, 
> just like you can with a resistor-terminated folded dipole.  What these 
> types of antennas show is that, no matter how bad an antenna design is, 
> it'll work sometimes.  TANSTAAFL!
>
> Mike / KK5F
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