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Message-ID: <001901cd5070$2a261330$4001a8c0@lark>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
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Date: Fri, 22 Jun 2012 13:09:38 +0100
MIME-Version: 1.0
Subject: Re: LF: Re: InV  L  Top  wire  config  - Best Option ??
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Ok wrong interpretation in the last email. The folded back section would
seem to be a "spoiler" to me. It would seem to me to be better to slope it
away out of the plane of the top-wire and radial (out of the plane of the
drawing) if possible. I "think" this would give some advatage :-))

Alan


----- Original Message ----- 
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
Sent: Friday, June 22, 2012 12:01 PM
Subject: Re: LF: Re: InV L Top wire config - Best Option ??



oK Alan

This  would be the  lay-out, the  lower  run  would  be  about   10  ft  up
from the   raised  radial , which may  increase  the ae amps in the
vertical section ?
when you   say  , reduce the  affective  height , .......  top  wire  is
still  at   40  ft  , far end of the  top  wire  slopes to  ground  as is ,

This  may  increase the  amps  to  ground  , at the  far end of the  top
wire , then  cause the  vertical   section  feed  to  increase ?



G.









From: Alan Melia
Sent: Friday, June 22, 2012 1:22 AM
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Re: InV L Top wire config - Best Option ??


Hi Grahan .mmmmm 10 feet?? that could reduce your effective height to 10feet
makingi it 6dB (maybe not quite that bad) worse than the 40 foot pole on its
own. The only plus point would be if that "radial" gives you a substantial
reduction in ground loss.....which I doubt is the case.

Seriously you do need to measure it to get the best out of a difficult
situation.......no amount of urban myth will give the right answer. Remember
higher "aerial current" is no use if its going straight to ground (like a
shunt cap across the feed point) and not traversing the radiation
resistance. You want as much current as possible to flow though the
radiation resistance (the vertical bit connected to the feed point) then you
want a big cap (=low impedance) from the top of the loading coil  to earth
for the "return current" (low loss resistance)  Not a very technical way of
describing it :-))  even capacitance from the active pole to ground gives
some loss....the inductive top load reduces that by reducing the voltage on
that section.

Alan