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[TowerTalk] Re: [Antennas] link tuners

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Subject: [TowerTalk] Re: [Antennas] link tuners
From: (Chuck (Jack) Hawley)
Date: Wed, 12 Nov 1997 08:38:27 -0600

L. B. Cebik wrote:

> I have saved some 55 messages so far related to interest in the
> re-emergence of a link-coupled tuner on the market--and I know some did
> not get saved along the way.  Interest is split between low and high power
> versions.  An interesting sidelight is that over half express interest in
> a kit--perhaps because it is something macroscopic that can be built

Hi LB,
I'm interested too. I favor a kit that supplies the enclosure mostly (the
hardest thing to make).....the inside components are obtainable but also
welcome in a kit. The problem I have is deciding how to tune the thing.

I have made a breadboard with a multitapped B&W 3033 coil with the input coil
of about 13 turns in the center and separated from the rest of the 3033 by a
turn or so of distance. The rest of the coil is about 10 or more turns on a
side. I have a 1000pF in series with the input and a dual 250pF in series with
the two output coils, the center of the the dual cap connected to ground. I
have added a 2000 pF variable in parallel with the dual also.  I am using the
series configuration for the secondary because I have something like 25 ohms
and some reactance on 160M and 80M, and 50 to 85 ohms on 40M measured with a
Palomar noise bridge from my 200 ft dipole fed by 4 inch, #12 open wire (about
78 feed of feedline).

I have tuned this breadboard and antenna-feedline on the three bands and come
up with several configurations for any given frequency. I can't decide which
combinations of #of turns of primary to use with # of turns of secondary. I am
tempted to minimize the total # of turns in general, but it is not clear to me
that that is the most efficient configuration. There is also something to say
for not having to switch taps for one end of the band to the other (happens
going from 1.8Mhz to 2.0Mhz). I feel more comfortable with the simple
unbalanced reversable L in that there is only one set of values that can be
found. I also can calculate the loaded Q of unbalanced pi and tee
configurations and see that I am using the lowest loaded Q when using these
tuner circuits. I haven't been able to figure out how to do this for the link
coupled tuner yet.

I am looking forward to your tutorial.

Chuck, KE9UW

Charles (Jack) Hawley
Chuck....Ham Radio KE9UW
AKA "Jack" BMW Motorcycles, MOA #224 K100RS
Wife rides...Viki, MOA #18120 K100RS
President IBMWR
Sr. Research Engineer Emeritus
University of Illinois, Urbana-Champaign

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