Message-ID: <24138943.952455770288.JavaMail.imail@bubbles.excite.com>
Date: Tue, 7 Mar 2000 11:02:50 -0800 (PST)
From: "john sexton" <computernetworks@excite.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: antennas for 136kHz
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Hi Rik,

This is excellent stuff and very opportune. I have been struggling to work
out what antenna will work best for me, and with Laurie's help using EZNEC
(thanks Laurie) have evaluated a serial meander system and a top-loaded
vertical with a big coil at the top and horizontal or down sloping
toploading wires. The trouble is that without fully understanding what is
going on it is difficult to interpret the results from EZNEC. Your article
has come at just the right moment. I hate the idea of putting something up
and then finding that it doesn't work. There is no substitute for
understanding. I have a feeling that it should be possible to achieve the
full 1 watt out, without having to put up enormous towers.

If I may I would like to pose a simple question, to which all the experts
are invited to reply:
If to the top of a vertical an equal vertical descender is added, insulated
from Earth at the bottom, but otherwise the same length as the original
vertical and coming straight down (like an old-fashioned hair-pin), and
assuming that this is resonated and matched to 50 ohms, will the new antenna
radiate more power, less power or the same power for the same input and why?
This might for example be the other wire of a sufficiently well spaced
feeder (no voltage breakdown), effectively short-circuited at the top and of
low RF resistance.

73s and all the best.

John, G4CNN


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