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Re: LF: Re: Re: 500kHz Portable

To: [email protected]
Subject: Re: LF: Re: Re: 500kHz Portable
From: "Mike Dennison" <[email protected]>
Date: Tue, 12 May 2009 10:29:28 +0100
In-reply-to: <003801c9cfed$3754c170$0301a8c0@mal769a60aa920>
References: <[email protected]>, <003801c9cfed$3754c170$0301a8c0@mal769a60aa920>
Reply-to: [email protected]
Sender: [email protected]
> 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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