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The folded back , open Box , is
the most simple to try , the radial , is
90 feet long and 6 ft off the
ground , earthed at the common point in the shed ,
open at the far end , so in terms of
capacity ,it would be 2 wires , 10 ft
apart , 25/30 feet long .......approaching the
vertical section at 90 deg
Unfortunately, the house support is lower
than the top of the mast and the wire
drops 30 deg or so down , I did have
the top section in a U shape , that did increase
the level from radio-mside , but the windage
was high ..... wx still heavy rain, so ,
rain stops play !
Tnx -G..
Sent: Thursday, June 21, 2012 10:57 PM
Subject: Re: LF: Re: InV L Top wire config - Best Option
??
Hi Graham, without measuring it I would not be
sure. It is no good trying to simulate this because these factors are not
included in the models. I think putting wies under one another is like folding
the plate of a cap back on itself. The total capacitance doesnt
increase. Think of the top-wire geometry as a skeleton (wire frame) of a
parallel plate capaitor with the other plate being ground (radials, ground
wires, whatever). My feeling based on my (and 136 friends) experiments suggest
that any drooping of the top will reduce the radiation resistance. Whether this
exceeds the effect of the increased capacitance is not possible to
esttimate. If you try it, and measure it, I would be very interested in the
results (never mind the theories.....show me the measurements :-))
) We only learn when somebody tries something......Mike's top-loads, and
Laurie's top capacity being great examples of structures that did not, for a
variety of reasons, show any advantage in theoretical efficiency
calculations.
There is little professional work, I know of, that
could give guidance.......the professionals don't (don't need!) use small
aerials. You cannot just "scale frequency" because many of the important factors
dont scale, or dont get included correctly in the
scaling model.
Alan.
----- Original Message -----
Sent: Thursday, June 21, 2012 9:59
PM
Subject: Re: LF: Re: InV L Top wire
config - Best Option ??
R Alan,
Down to one of Mr Hobson's fine
designs here , the under slung wire
, would be the simplest to arrange , say
it ran 10 ft above a 90 ft
elevated ground radial , now would
that xtra C , increase the amp's in
the vertical section , the other side of
the top coil ...?
Other wise its ,just possible to run 90
deg about 20 feet , 90 then down , at
the far end
I tune using a swr meter , usually get a
sharp dip with the variometer , but I
also have a old 1000 pf 4 gang
clipped , low over the auto transformer , that is
handy , just takes the final 'ref down
and as its low , there is no flash over ,
bit like a band-spread on a rx oscillator coil
Testing wise , luckily , I can reach the Delft
web-sdr in the day time , so can
do s/n checks at range using
ROS-MF-2 , the s/n is the
average along the time line , so quite
accurate
Still raining
73 -G..
Sent: Thursday, June 21, 2012 8:59 PM
Subject: Re: LF: Re: InV L Top wire config - Best Option
??
Hi Graham its not exactlyaerial weather here
either :-((
The problem with unconventional "shapes" is you
will have to just try 'em out. I have always concentrated on reducing ground
loss as the most effective use of time and effort. Best done by measurement,
and not urban myths :-)) Thats why I always plug a simple
transformer coupled bridge, oscillator and receiver as a detector, noise
bridges have never worked at LF for me ....probably too many BC stations close
by. I also like bridge measurements......its probably an "age thing"
:-)) I feel closer to the problem and able to employ some skill and
maybe dexterity, even if I dont get the numbers on the readout of a
VNA......at least I learnt to sense when the measurement "feels" right. It is
the classic substitution measurement with passive references.
Alan
G3NYK
----- Original Message -----
Sent: Thursday, June 21, 2012 6:48
PM
Subject: Re: LF: Re: InV L Top wire
config - Best Option ??
R Alan.
Horizontal spread ......missing at the moment
... will have another look out
side , when the rain stops , horizontal
open box may be possible ..just
Tnx -G..
Sent: Thursday, June 21, 2012 4:42 PM
Subject: LF: Re: InV L Top wire config - Best Option
??
Hi Graham it basically doesnt matter too
much :-))
The thing is to get as much wire as high as
possible. Yes fold it back, meander it....spacings less than about 2 feet
dont add much over a single wire. Drop the end if you have to but remember
this may reduce the signal slightly in that direction....but it will
increase slightly the capacity to ground. be careful of the dropped ends
they are high voltage points and may not be "family friendly"
...... doubling the capacity to ground ( note ground....not lossy
roofs/foliage underneath) will probably halve you ground losses. It will do
very little to increase the radiation resistance.
Your diagram is difficult to read but running
one of the wires directly under another will be of no benefit and may be
worse than not having it......horizonltal spread is what you want, so pull
it at least 2 feet aside before folding it back.......I think you get the
idea.
Alan
G3NYK
----- Original Message -----
Sent: Thursday, June 21, 2012 4:17
PM
Subject: LF: InV L Top wire config -
Best Option ??
InV L Top wire config - Best Option
??
Any thoughts on the best configuration for
the top wire ??
Tnx -G,
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