-----Original Message-----
From: Mike Dennison [SMTP:[email protected]]
Sent: Monday, June 21, 1999 2:27 PM
To: [email protected]
Subject: LF: Antennas
I have done very many antenna experiments over the past 2-3
years to get a better signal at 73 and 136kHz from a small garden.
I have experimented with inverted-L Marconis. These have mainly
sloped down from the top of the vertical section and I have on two
occasions increased the height of the far end with improved results.
It seems that at LF you cannot get away with drooping the far end
of an inverted-L like you can at HF. This is presumably because
the current distribution is approximately linear for a short Marconi
and sinusoidal for something a quarter-wave or more.
[CBQ>] You don't get away with it on HF either. My experience on
160 is that inverted-Ls invariably work better with horizontal tops rather
than sloping ones, possibly losses associated with the high voltage end of
the aerial are lower and the radiation resistance is higher.
There was a QST article dealing with this some while back (I'm sorry
but I don't recall the issue). The conclusion was that sloping the far end
below ~50% of the height of the vertical section was counterproductive.
Also, if I run three top wires in parallel, should I join them at
the far
end?
[CBQ>] I recall another QST article (but not the date of issue)
that dealt with broad-banding an 80 metre dipole using a multi-wire top.
The advice was not to connect the parallel wires together at the far end,
though I can't remember why.
Cheers,
Phil, GJ4CBQ.
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