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" <[email protected]>
To: <[email protected]>
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: [email protected]
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
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