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Message-ID: <3.0.1.16.20010119105824.2c077f56@mail.cc.kuleuven.ac.be>
Date: Fri, 19 Jan 2001 10:58:24
To: rsgb_lf_group@blacksheep.org
From: "Rik Strobbe" <rik.strobbe@fys.kuleuven.ac.be>
Subject: Re: LF: Loading Coils
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Hello Roger,

I hadn't thought of the loading coil that way (never too old to learn ...).
It sounds interesting to me as my loading coil consists of 3 parts :
- a 2.5mH coil at the top of the vertical part
- a big (7mH) coil that can be tapped, at the moment I am using only 0.5mH
of if (so a lot of 'useless copper' arround
- a smaller coil that can be adjusted between 0.8 and 1.3mH by sliding a
ferrite rod (now without the rod in in, so 0.8mH)
In an attempt to be smart I placed the small coil horizontal (to avoid that
the ferrite rod would 'slip away' by gravity) and the big coil vertical (to
minize coupling between the 2 coils). Both coils are on a plastic box abt.
0.4m from the ground and abt. 0.3m separated.
I wonder if I would gain anything if I placed both coils vertical ?
Also it is attempting to try the plate under the coils, for a first try I
could cover the plastic box with alu-foil (household) or is this a too thin
metal layer ?
If I find some time over the weekend I will try to do some tests.

73, Rik  ON7YD

>The loading coil is not just a matching device, it is also a primary source
>of vector potential and it is the vector potential, rather than its
>offspring, the magnetic and electric fields, which is the fundamental
>source of electromagnetic radiation.  It is therefore advantageous to place
>the coil upright at the base of the antenna.  Furthermore, as a large
>component of the vector potential is locally concentrated in this region,
>it may be possible to gain a few dBs by placing an aluminium or copper
>plate, somewhat larger than the diameter of the solenoid, a few centimetres
>under the solenoid, insulated from the earth but it may be connected
>directly to the TX ground terminal.