Message-ID: <00cd01c3cfd8$98f53c40$fdc428c3@bryan2>
From: "captbrian" <captbrian@ukonline.co.uk>
To: rsgb_lf_group@blacksheep.org
References: <6.0.1.1.2.20031227144750.035a8d70@POP3.freeler.nl> <000101c3cd6d$6ee77de0$0dcefc3e@l8p8y6> <006001c3cd86$3add4fc0$441686d4@bryan2> <6.0.1.1.2.20031229124828.027e8af0@POP3.freeler.nl>
Date: Wed, 31 Dec 2003 19:41:12 -0000
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Subject: Re: LF: Re: Re: "T" versus "L"aerial
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I agree entirely
B
----- Original Message -----
From: "Dick Rollema" <d.w.rollema@freeler.nl>
To: <rsgb_lf_group@blacksheep.org>
Sent: 29 December 2003 12:03
Subject: Re: LF: Re: Re: "T" versus "L"aerial


> Dear Bryan,
>
> Because the aerial  system is very small, expressed in wavelength, the
> voltage on all wires "above" the loading coil will be the same; unless
> there is another loading coil between the vertical and horizontal parts of
> the "T".  When the two horizontal parts have equal capacitances to earth
> the current distribution on these wires will be similar and that will also
> be the case for the two vertical wires of the "double L".  In case of
> unequal capacitances the current in the vertical wires will be different.
> But because the wires are very near to each other they act as a single
> radiator carrying the sum of the currents in the two wires.
> So for all practical purposes there is no difference in performance of the
> "double L" and a real "T".
>
> I use the "double L" instead of a real "T" because the aerial is also used
> as a multiband dipole with open line feeder on 160m and the HF bands.
>
> 73, Dick, PA0SE
>
> At 22:04 28-12-03, you wrote:
> >I find it difficult to believe that there is any different loading seen
at
> >the bottom of two L's in parallel but with opposing horizontal parts from
> >that seen by a single wire vertical to the Tee or that there is any
> >different current distribution or radiated pattern.
> >
> >If there are those that do not then I ask::
> >what is the voltage difference between the two vertical wires at their
> >respective junctions with their own horizontals ?
> >
> >Bryan G3GVB
> >
> >
> >
> >----- Original Message -----
> >From: "hamilton mal" <g3kev.ham@virgin.net>
> >To: <rsgb_lf_group@blacksheep.org>
> >Sent: 28 December 2003 18:04
> >Subject: LF: Re: "T" versus "L"aerial
> >
> >
> >
> >   ----- Original Message -----
> >   From: Dick Rollema
> >   To: LF-Group
> >   Sent: Saturday, December 27, 2003 2:09 PM
> >   Subject: LF: "T" versus "L"aerial
> >
> >
> >   To All from PA0SE
> >
> >   Further to my e-mail of 26 December I measured the field strength as
> >radiated by the aerial in
> >   Inverted L-configuration. From this I found EMRP = 57 milliwatt.
> >
> >   This confirms the benificial effect of top loading. The T-aerial
radiated
> >140 milliwatt.
> >
> >   So going from a single 20m top load wire for the "L" to 2 x 20m for
the
> >"T" resulted in an improvement by a factor 2.46 (3.9dB) in radiated
power.
> >
> >   The vertical part of the "T" consisted of an open wire feedline of 11m
> >with the two wires connected in parallel in the attic shack. For the "L"
one
> >of the feedline wires was removed. I assume this did not appreciably
affect
> >the EMRP.
> >   HI Dick
> >   From your explanation using open wire feeder you are using an inv L
with
> >one feeder wire connected and with the 2 feeders strapped at the shack
end
> >then you have two inverted  L antennas in parallel. A true T antenna has
> >both feeder wires connected at the top as well as the bottom, in fact do
not
> >use open wire feeder, connect one wire to the centre of your T horizontal
at
> >the top and the bottom of your single wire to the loading coil and
matching
> >unit.
> >   73 de Mal/G3KEV
> >
> >                             .
> >
> >   73, Dick, PA0SE
>