Message-ID: <001f01c3d037$ca6b1560$b1e486d4@bryan2>
From: "captbrian" <captbrian@ukonline.co.uk>
To: rsgb_lf_group@blacksheep.org
References: <000001c3d009$acf7a620$c7e47f50@Smisan>
Date: Thu, 1 Jan 2004 07:20:50 -0000
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Subject: Re: LF: Re: "T" versus "L"aerial
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If two 20m  wires are better than one 40m  one for the same total lenght of
wire , Does this mean that four horizontal legs of 10 m would be even better
? and so eight of 5m or sixteen of only 2.5m better still ?

How about

64 X 625mm ? or......

just a disc of foil 1000mm dia.?

Perhaps there is an optimum number of horizontal wires?
If just a 1000mm disc then why not have one at the bottom instead of earth?

Why does the name Hateley come to mind ? ;-)

Bryan
Bryan G3GVB

----- Original Message -----
From: "M. Sanders" <misan@xs4all.nl>
To: <rsgb_lf_group@blacksheep.org>
Sent: 01 January 2004 01:50
Subject: RE: LF: Re: "T" versus "L"aerial


> Dear Dick / Bob and Lofers,
>
> Does the computer calculate the earth losses in the return path from the
> aerial system to the transmitter? If it would then the earth losses in a
> T should have been significantly less then the L alternative. There are
> two separate return currents
> (parallel resistance) and each with a smaler physical length (lower
> R-earth)  in a T system resulting in more ERP if compared to an L
> system.
>
> Greetings and best wishes for a (LF) radio-active 2004 to All.
>
> Mike, PC4M (ex PA3BSH)
>
> -----Oorspronkelijk bericht-----
> Van: owner-rsgb_lf_group@blacksheep.org
> [mailto:owner-rsgb_lf_group@blacksheep.org] Namens Dick Rollema
> Verzonden: maandag 29 december 2003 16:37
> Aan: rsgb_lf_group@blacksheep.org
> Onderwerp: Re: LF: Re: "T" versus "L"aerial
>
> To All from PA0SE
>
> Bob, ZL2AC wrote:
>
>
>
>
> Dick PA0SE,
>
> Fine on the test result.  As you stated, the tested T has twice the
> amount of top loading wire (2x 20 metres) than the L (1x 20 metres).
>
> It would be interesting to know if a T is better than an L for constant
> length top loading i.e. what the difference is if the upwire joins at
> the end or the middle of the horizontal top wire (theory suggests the T
> is better as there is minimal horizontally polarised component).
>
> Bob,  I cannot answer your question by a practical experiment but used
> computer simulation instead by means of K6STI's program Antenna
> Optimizer.
>
> I modeled two antennas with a vertical element of 20m.  One an Inverted
> L-antenna with a horizontal top load wire of 40m. The other a T-antenna
> with a top load of 2 x 20m.
> Both antennas  without losses, over perfect ground and fed with 1kW.
>
> At a distance of 10km (so well outside the near field region) and over
> perfect ground both antennas produced a vertically polarised field of
> 29.9mV/m. The horizontally polarised field was zero; but this is to be
> expected because over a perfect conducting ground a horizontal field
> component cannot exist.
>
> 73, Dick, PA0SE
>
> Original message:
>
>
>
> To: LF-Group <mailto:rsgb_lf_group@blacksheep.org>
> Sent: Sunday, December 28, 2003 3:09 AM
> 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.
> 73, Dick, PA0SE
>