I agree entirely
B
----- Original Message -----
From: "Dick Rollema" <[email protected]>
To: <[email protected]>
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" <[email protected]>
>To: <[email protected]>
>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
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