From: "G4WGT Gary" <g4wgt@talkgas.net>
To: "Rsgb_Lf_Group" <rsgb_lf_group@blacksheep.org>
Date: Sun, 4 Jan 2004 10:55:03 -0000
Message-ID: <INELIKBPOHPEDFDGMOKHEEIOCDAA.g4wgt@talkgas.net>
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Subject: LF: Antenna's
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Hello again to all at LF,

Happy New Year to you all.

I have had a few days away over NY so I had quite a lot of e-mails to look
thro'.
I see that there has been some debate on antenna's again which suits me fine
because I am considering trying to improve my LF antenna system. I need to
improve on the support & insulation of the antenna since my recent
experience with corona bringing down part of the antenna, so I going to try
a different antenna arrangement at the same time.

I have only got a small back garden & at the moment the arrangement is like
a 80 to 90 mtr loop pulled in to the centre from the middle of the sides &
then pulled upwards to the top of my 14 mtr mast & secured at the lower
corners, this makes it take up a lot less space for the amount of wire used
(An example of the shape is like a Maltese Cross with the centre up in a
peak & the wide sides of the cross sloping steeply downwards). The "loop" is
fed with 72 ohm twin feeder at the peak which allowed me to use it on the 80
M (3.5 Mhz) band with a balanced matching unit. Using this gave a great
increase over the umberella top loading with 4 wires following the criteria
set out on one of the web sites (I think Rik ON7YD).

The new arrangement will basically be like a large bow tie shape using about
160 to 180 mtrs of wire (which is considerable more wire than the other
version), the wide ends of the bow tie shape will be about 7 metres across
10 to 12 metres long & pinched together near the centre were it will be
pulled up to the top of the mast. I am not sure if I should feed it at the
centre (top of the mast) like a centre fed inverted V or feed it at the end
like an end fed inverted V. I have seen article on the web relating to
"umberella) top loading that suggests that if the top loading wires come
down steeply that the vertical part of the antenna can be shielded &
detracts from the performance as a vertical radiator, also that if the
feeder is close to the metal mast that supports it that this also reduces
performance, also it has been said that it is probably better to cover as
much ground area as possible with loading wire in the space available .

 I would like you to look at a diagram of my idea (which is reasonably to
scale) & give me your comments. This can be found at :-

www.wgtaylor.talkgas.net/coilcabinet.jpg

I have substituted the existing picture with the diagram hence the name
coilcabinet.

Please your comments direct or via LF reflector.

Thanks & 73

Gary - G4WGT  g4wgt@talkgas.net