As you may be likely aware, I did build a tuner, specifically a balanced
tuner, mostly for 160M and 80/75M and be able to handle legal limit power.
While it does an excellent job on any frequency less than 18 MHz, I find
that trying to use it on frequencies above 18MHz is a challenge.
Several factors contribute to such, being physical size of the rollers, the
leads between components and such. In fact, after further investigation,
I've found several resonances above 18 MHz where it will actually "load
itself" with a short across the output terminals or even another
configuration with the output terminals not having any connections. These
configurations and issues were identified as existing with several
commercially made tuners recently evaluated by ARRL Lab.
I'd agree that if you intend to work 160M and 80/75M and to some extent 40M,
one should use a dedicated tuner that is better suited for those
frequencies. Then for those bands above 10 MHz a second tuner better suited
for those would likely be more efficient and less problematic. I'll likely
build a smaller tuner using smaller value inductors and smaller capacitor
value as a Winter project. My objective is at design to operate 30M -> 6M,
up to legal limit power with about any wire and feedline combination I so
choose.
For vertical antennas, I find that a matching network at the base of the
vertical is best. In the BC world it is called a "matching network" or
"tuning unit" and in the ham radio world it is commonly known as an "antenna
tuner". Same stuff......different name. In either case the objective
is to match the load Z to the feedline Z at the base of the vertical
radiator. Thus the feedline is operating at a nominal 50 ohms with a
minimally reactive load appearing to the transmitter. If one chooses to
change bands or even to some extent frequencies, they should have some form
of variable network being usually required at the base of the vertical
radiator.
I do have pixs of the current tuner if one so desires.
73
Bob, K4TAX
----- Original Message -----
From: "Jim GM" <jim.gmforum@gmail.com>
To: "TenTec-request" <tentec@contesting.com>
Sent: Wednesday, November 06, 2013 1:16 PM
Subject: Re: [TenTec] 160 M antenna
Rick, I like your answer. I agree with the others too.
Make the external tuner for 160, and 80 and auto tuner, with a remote
bypass so you can use the tuner in the sack for the other bands. Mount the
160/80 tuner out side close to the radial field.
160M is a pain in the but, to get it working. BCI messes up my analyzer
so
it is a work in progress and trial and error. Just too close to the
transmitter sites.
--
Jim K9TF
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