LF: TA on 500

To:	rsgb <[email protected]>
Subject:	LF: TA on 500
From:	"lawrence mayhead" <[email protected]>
Date:	Thu, 6 Mar 2008 11:35:09 +0000
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Hi Paul,
Apart from any "ASPERGER" problem, your comments re. Ant. design are very interesting.
In the 73/136 days, getting ground losses down so that one could approach 1W erp with anything
less than 1000W, Tx power dictated as much top wire as possible (in fact I needed 600ft and then
could only manage 150mW on 73kHz). So the dice was loaded in favour of those of us fortunate
enough to be able to put up such large arrays. On 500kHz however its a much more level playing field.
1W can be obtained with much less Tx power and more modest Ant.arrays. Modelling wilh Eznec
shows that a top wire of equal length to the vert. section results in optimum if not max. radiation
resistance and manageable ground loss. But more importantly as you say the elevation plot shows
a considerable null in the vertical plane (up to 30db) whereas my large array is only 6db down in the
vertical , so a lot of energy going straight up !
Thanks for pointing this out, no doubt other stations boasting very large arrays will take note.
73 Laurie.

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