Len,
An inverted L is a 1/4 wavelength antenna that, when fed from the end near
the ground, can be fed with coax WITHOUT a coil/capacitor combination. The
center conductor goes to the antenna wire, the shield goes to a grounding
network of radials.
A coil/capacitor combination is needed when you feed a high-impedance
antenna like a half-wave fed at the end, or (and here's an example of)
something fed at the high-impedance end of an element like a bobtail
curtain: http://www.n8sfc.com/bobtail.gif. This shows a general diagram of
how the "tuner" is organized. It's function is to transform the high
impedance of the antenna to the lower impedance of the coax. In this case,
not much current flows at the high-impedance point (by definition), so a
super-duper ground is not as important as with an inverted L.
Good luck!
-Rex-
K1HI
Rex Lint
Merrimack, NH
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Len snyder
Sent: Sunday, October 19, 2008 10:26 PM
To: towertalk@contesting.com
Subject: [TowerTalk] parallel tuning network
I am trying to build a parallel tuning network for a 160 Mtr.
inverted L. I have a variable capacitor and a roller inductor which I
wish to hook up to help tune the inv. l. The cap and inductor are
both made by the Johnson Co. The cap is model # 154-2-3 and the
inductor is number # 229-201.
My problem is that being electronically challenged and very new to
ham radio, I don't know how to hook the items up to make them work
properly. They are from a Johnson Viking set and I am hoping that I
can make them work to tune the inv. L.
I really don't know which end is which or where the different wires
should be attached. I've done several searches on the net but have
been unable to find any info that will tell me what I need to
know. Any information you can give me will be greatly appreciated.
Thanks, Lennnie. KD8CWP
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