Antennas GP type

Answer for rec.radio.amateur.antenna

 
In aim of avoidance of large of resistance of the ground onto efficiency of antenna it complies, there where this is possible antenna with earthing plane. Plane such can create in peculiarity some, often 4 rods about length ¼ wave asembled together. Upper part, it is connected electrically from ground radials is fixed on separating insulator directly to central of coax cable.
Angle Θ between vibrator and ground radials it influences character of radiation on resistance of antenna and her character of radiation (G6CJ).

Ra=18[1+sin(Θ-90°)]²=18(1-cosΘ)² [Ω]
for:
Θ=180°  Ra=72Ω
Θ=132°  Ra=50Ω
 Θ=90°  Ra=18Ω

It marks this, that material does not have, from which he became executed mast and whether joint electrical became with antenna (ground radials). ntroducing steel mast between ground radials (so as in my construction) minimum is very on resistance of antenna and it it was been possible to skip him.
It meets yet change of joint of GP antennas conected elecrical with mast also earthed. At longer waves where antenna is large and heavy use of insulator at basis is inconvenient. Bottom point of antenna is it has scarce potential in relation to the ground and may be earthed maybe. Power supply then be holds transformer Gamma.
Photo: Isulator of antenna GP o length about 100 m (300ft).

© 2002-05-16 SP4IZK

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