Yes your right on that Mike,
If you model a T and then change it to arrow shape , once the free ends
are more than about 6 feet off the ground the radiation and feed values
are all over the place ..you would not of realised in the field, what was
going on !
G .
--------------------------------------------------
From: "Mike Dennison" <[email protected]>
Sent: Tuesday, May 12, 2009 10:29 AM
To: <[email protected]>
Subject: Re: LF: Re: Re: 500kHz Portable
You do not need 2 masts for an inv L or T antenna.
The so called horizontal wire(s) can slope down and the far end tied
to a bush or tree, or a stake in the ground via an insulator, as far
away as possible from the vert section, the longer the better. Keep it
simple. mal/g3kev
This is quite wrong. Any slope downwards will reduce the effective
height of a Marconi. Since ERP is a function of the square of the
effective height this is extremely important. An umbrella is far
preferable to an inverted-L in a single mast situation because a
large amount of capacitance to ground can be achieved without much
reduction of effective height.
Based on my experience of LF portable (both on 73 and 136kHz), my
advice is to make very sure that the remote ends of a Marconi are
very well insulated as they carry large voltages. Keep well away from
wet trees. This is not just a safety issue; any voltage leaked is
power lost.
Mike, G3XDV
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