ongoing thought, If you use half the fixed coil and all of the varying coil
in series [ F/2 - V ] you should come near to zero inductance with coils
in opposition - certainly quite a low value. Cleverer men than I will put
figures on these thoughts.
Bryan
----- Original Message -----
From: "captbrian" <[email protected]>
To: <[email protected]>
Sent: 05 July 2006 18:58
Subject: LF: Re: Re: Re: Antenna Tuning
> 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
> >
> >
> >
> >
> >
> >
> > --
> > Internal Virus Database is out-of-date.
> > Checked by AVG Free Edition.
> > Version: 7.1.394 / Virus Database: 268.9.5/377 - Release Date: 27/06/06
> >
> >
>
>
>
>
>
> --
> Internal Virus Database is out-of-date.
> Checked by AVG Free Edition.
> Version: 7.1.394 / Virus Database: 268.9.5/377 - Release Date: 27/06/06
>
>
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