Message-ID: <005d01c0d676$c9eb4d20$436f78d5@btopenworld.com>
From: "G3YXM" <G3YXM@wireless.org.uk>
To: rsgb_lf_group@blacksheep.org
References: <003e01c0d673$f5006200$9b9401d4@g4jnt>
Subject: LF: Re: Re: Measurement of antenna current
Date: Sun, 6 May 2001 22:52:04 +0100
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Dear all.

I was always taught that the current at the top and bottom of the coil would
be the same "unless the coil was radiating power", as your coil is
significant in size relative to the total aerial system I can see that the
power raiated from the coil could account for the difference?

Or is that cobblers?

Dave G3YXM.

----- Original Message -----
From: Andrew Talbot <G4JNT@thersgb.net>
To: <rsgb_lf_group@blacksheep.org>
Sent: Sunday, May 06, 2001 10:31 PM
Subject: LF: Re: Measurement of antenna current


> I would have thought the stray capacitance associated with the ammeter
when
> measuring current at the top of the coil would cause more than enough
> detuning to reduce the current by this much.
>
> But there could still be a slight variation due to the effect you
describe.
> Wouldn't you be better tapping up from the bottom or using a variometer
than
> tapping down from the top ?
>
> Andy  G4JNT
>
>
> -----Original Message-----
> From: Steve Rawlings <steve@alg.demon.co.uk>
> To: LF Group <rsgb_lf_group@blacksheep.org>
> Date: 06 May 2001 22:11
> Subject: LF: Measurement of antenna current
>
>
> >Hi All,
> >
> >Today, I made some more antenna current measurements on my 12 m
> >vertical (and my shiny new loading coil), using a thermocouple
> >meter.
> >
> >At resonance, the current into the base of the loading coil, was
> >2.2 A.  But when measuring the current into the antenna at the
> >hot end of the coil, the meter only indicated 1.8 A.  I had
> >expected the reading to be the same at both ends of the coil.
> >
> >The loading coil has many more turns than is required to resonate
> >the 12 m vertical, so the connection to the antenna uses a tap
> >which is several turns down from the top of the coil.  I've been
> >thinking that the excess turns at the top of the coil may be
> >causing the difference in current readings.  (This may sound
> >silly, but in my mind's eye, I can sort of picture some of the
> >current in the coil going into the capacitance of the antenna;
> >and some current going into the capacitance of the unused turns.)
> >
> >Before I try removing the excess turns, I'd like to know whether
> >the current should indeed be the same at both ends of the loading
> >coil.  Can anyone help?
> >
> >Regards to all,
> >Steve GW4ALG
> >
> >
>
>
>