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
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