Return-Path: Received: (qmail 61382 invoked from network); 29 Dec 2003 12:05:43 -0000 Received: from unknown (HELO ptb-mxscan02.plus.net) (212.159.14.236) by ptb-mailstore01.plus.net with SMTP; 29 Dec 2003 12:05:43 -0000 Received: (qmail 18226 invoked from network); 29 Dec 2003 12:05:43 -0000 X-Filtered-by: Plusnet (hmail v1.01) X-Priority: 3 X-MSMail-Priority: Normal X-Spam-detection-level: 11 Received: from ptb-mxcore02.plus.net (212.159.14.216) by ptb-mxscan02.plus.net with SMTP; 29 Dec 2003 12:05:42 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1Aaw9V-0004d9-VI for dave@picks.force9.co.uk; Mon, 29 Dec 2003 12:05:42 +0000 X-Fake-Domain: majordom Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Aaw8i-0006H8-Jc for rs_out@blacksheep.org; Mon, 29 Dec 2003 12:04:52 +0000 Received: from [213.218.75.236] (helo=smtp07.freeler.nl) by post.thorcom.com with esmtp (Exim 4.14) id 1Aaw8h-0006Gy-Dx for rsgb_lf_group@blacksheep.org; Mon, 29 Dec 2003 12:04:51 +0000 Received: (qmail 18389 invoked from network); 29 Dec 2003 12:04:51 -0000 X-Fake-Domain: unknown Received: from unknown (HELO w8k3f0.freeler.nl) ([62.21.138.38]) (envelope-sender ) by smtp07.freeler.nl (qmail-ldap-1.03) with SMTP for ; 29 Dec 2003 12:04:49 -0000 Message-ID: <6.0.1.1.2.20031229124828.027e8af0@POP3.freeler.nl> X-Sender: FRE0000086604@POP3.freeler.nl (Unverified) X-Mailer: QUALCOMM Windows Eudora Version 6.0.1.1 Date: Mon, 29 Dec 2003 13:03:08 +0100 To: rsgb_lf_group@blacksheep.org From: "Dick Rollema" In-reply-to: <006001c3cd86$3add4fc0$441686d4@bryan2> References: <6.0.1.1.2.20031227144750.035a8d70@POP3.freeler.nl> <000101c3cd6d$6ee77de0$0dcefc3e@l8p8y6> <006001c3cd86$3add4fc0$441686d4@bryan2> MIME-Version: 1.0 Subject: Re: LF: Re: Re: "T" versus "L"aerial Content-Type: text/html; charset=windows-1252 X-Spam-Checker-Version: SpamAssassin 2.60 (1.212-2003-09-23-exp) on post.thorcom.com X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.60 X-SA-Exim-Scanned: Yes Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-PN-SPAMFiltered: yes X-Spam-Rating: 1 Content-transfer-encoding: 8bit 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