[AMRadio] Antenna Tuner Wonderings


Brian Carling bcarling at cfl.rr.com
Thu Dec 23 05:44:55 EST 2004


DON - you were ROARING IN to Florida on 160m a few months 
back. Strongest signal on the band. I had assumed that you were 
using a full-sized vertical. Seriously!

I was considering a homebrew "Carolina Windom" for my
"soon-to-be-smaller-sized lot."

Brian, AF4K.

On 23 Dec 2004 at 0:03, Donald Chester wrote:

> 
> >What kind of "crappy" antennas are you using, i.e., doublets fed with coax,
> >open wire lines, etc., or end-fed wires?   Or, some combination of types 
> >maybe?
> >
> >
> >Rather that building up a bunch of tuners you might consider putting your
> >efforts into erecting a set of antennas that all worked directly off a 50 
> >or 75
> >ohm coax feedlines.   Half-wave dipoles, one for each band, for example, or 
> >one
> >or more of the multi-band arrangements (G5RV, fan and trap dipole, etc.).
> 
> I think the best solution would be to erect one good dipole, as high as you 
> can get it, for the lowest frequency band you operate.  If you don't have 
> that much space, consider a  shortened dipole for the lowest band.  Feed it 
> with open wire  line and a balanced tuner (not one of those bogus jobs with 
> unbalanced T or L network coupled to the balanced line via a balun).  I 
> prefer to make my multi-band tuners using plug in coils and split stator air 
> variables.  You should be able to transform the driving impedance of that 
> antenna to 50 ohms nonreactive on about any amateur frequency, without a 
> forest of separate dipoles growing out of the shack.  Then couple whichever 
> transmitter you are using to the tuner.
> 
> At present I use a system a little more complicated.  I still use one dipole 
> for all bands, but a separate tuner for each band.  That way the tuner is 
> pre-tuned to frequency and all I have to do is load the appropriate 
> transmitter into it and switch the feedline to it.
> 
> The dipole is cut for 80m, but I can load it up on 160 as a quarterwave 
> dipole with fairly good results.  It is about 110 ft. high, so the height 
> somewhat compensates for the shortness of it on 160.
> 
> I use a separate L-network to match the the quarterwave base-insulated 
> vertical on 160, which is  my main topband antenna.
> 
> 73, Don K4KYV
> 
> 
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