From: "Mike Dennison" <mike.dennison@rsgb.org.uk>
Organization: Radio Society of Great Britain
To: rsgb_lf_group@blacksheep.org
Date: Tue, 14 Sep 1999 09:32:39 +0100
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Subject: Re: LF: Advice on Antenna.
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M0AYF wrote:
> The final part of my L.F. project requiring construction is the antenna.
> Though I had decided on a "T" antenna I now find that due to a lack of
> viable supports for the top loading wires I may have to "re-think" my
> antenna. The vertical part /around 10 mtrs) is ok but I have a number of
> options for "top loading" and I should like to ask the opinion of
> yourselves as to the best option to choose from the following list:
> 
> 1) 10 mtr vertical only i.e. No top loading.
> 2) 10 mtr vertical with top loading "T" wires (7 mtrs each side) sloping
> downwards. 3) 10 mtr vertical with about 7 mts of horizontal wire at the
> top to form a sort of inverted "L" type antenna. 4) 10 mtr vertical with
> 3x7 mts of horizontal wire to give increased capacity.
> 

A simple 10m vertical will give you an effective height of only 5m. 
Top loading will increase this, and since the ERP is a function of the 
square of the effective height it is well worth doing. BUT avoid top 
wires that slope down as these will reduce the effective height. 
Shorter horizontal wires are preferable - the more the better. With a 
small top section - mine is less than 20m - it may be useful to have a 
coil at the top of the vertical section, as light as possible (with larger 
top sections the resistance of the coil tends to cancel out the 
advantage).

I look forward to our first QSO.

73


Mike, G3XDV (IO91VT)
http://www.dennison.demon.co.uk/activity.htm