First thought
It occurs to me you could use a chap ole' length of wire as a temporary
antenna and cut bits off it until you achieved resonance with the minimum
series setting of the variometer. That would give you a feel for how far
away from resonance you are and thus how many turns You may need to unwind.
Second thought.
You say both fixed and moving coils are divided in the centre.
Third thought.
Can you not tap into the joining wire at the centre and thus use half the
coil? That would give you choice of 4 combinations V/2 + F, F/2 + V, V/2
+ F/2, F+V
Bryan G3GVB
----- Original Message -----
From: "J. Allen" <[email protected]>
To: <[email protected]>
Sent: 04 July 2006 15:40
Subject: LF: Re: Re: Antenna Tuning
> Alan, Steve and All,
>
> Thanks for the feedback.
>
> The antenna is basically an inverted-L antenna. Using approximate
> dimensions, the vertical portion is a 110 foot tower, but the attachment
> point for the horizontal is down at about 100 feet. The horizontal is
> composed of two, 390 foot long wires that form a V with the included angle
> of about 50 degrees. The ends of the L wires are supported at about 70
feet
> and 63 feet and the wires are single span and have bout 10 or 12 feet of
sag
> for stress. The antenna is over a set of about 30, #11 radials of various
> lengths from 30 to 1200 feet in length. The soil is very dry sand in a
flat
> in the bottom bowl formed by mountains. The antenna is fed through about
> 250 feet of 50 Ohm hard line from the shack.
>
> At the base of the antenna, the vertical portion terminates at the input
of
> a Variometer the other end of which ties to the radial ground system. The
> variometer is currently link coupled to the coaxial cable, but the problem
> was there when the grounded side of the variometer was tapped up like an
> autotransformer, and also when the antenna was fed through a very large
> roller inductor / autotransformer. In fact there have been a number of
> different feed methods tried and all failed.
>
> If I am not mistaken, the antenna calculated at about 1500 pF.
>
> Nothing I have tried to date has resulted in successful tuning. The most
> power I have been able to sustain is about 30 Watts. Higher power has
> always resulted in smoke.
>
> The main limiting factor in all this work is the operator... I have
> symptoms of early Alzheimer's Disease, and get confused about what I am
> doing or where I am in a process. A written step by step which I could
> check off as I go would be a great asset.
>
> It is important to the Canadian and possible future US amateur plans for a
> LF portion on 137 that I be successful here. We have great resistance
from
> the power companies with their Power Line Carrier systems here. I am
> fortunate that I live in one of the two areas of Canada where 137 kHz is
> used for PLC, and the central purpose of my experiments is to get the
> station up to full power and show compatibility of PLC and amateur radio.
>
> I have had really wonderful support from Steve and Scott, and have both of
> the UK LF books as guides but still cannot seem to get the antenna tuned.
I
> am familiar with the use of an oscilloscope and maintained the PLC system
> which I am demonstrating non-interference with.
>
> As soon as I can get the antenna tuned properly, I can run the power level
> up and begin beaconing essentially 24/7 for the remaining months of our
> experiments.
>
> Has anyone produced a very detailed first time tuning guide for beginners
> like me? I am about 1000 miles away from the closest assistance
> (VE7SL/VE7TIL)
>
> Thanks again,
>
> JA
> VY1JA
>
>
>
>
>
>
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