[TowerTalk] Compromise Vertical antenna ground system?

[Thor Hallen]

The 1/2 wave vertical dipole is a conceptually different antenna from the 
classical 1/4 wave vertical and does not depend any ground system at all. 
It can be thought of as a normal horizontal dipole standing on end. The 
half wave verticals that are end fed like the Cushcraft series use a small 
counterpoise to reduce the drive point impedance for matching 50 ohms. The 
center fed 1/2 wave verticals do not use a counterpoise as they provide a 
good match to 50 ohms as is. The counterpoise is not a ground and the 
antenna will not function if you attempt to replace the counterpoise with a 
ground system. The end fed version can be thought of as a horizontal Zep 
standing on end with a capacitive hat.

The EZNEC antenna simulation program has a very accurate model for ground 
and can be specified to be anything from very poor like encountered in 
inner city to excellent as encountered over sea water. The simulation 
accuracy has be verified by many experiments comparing simulation to actual 
measurements of field strength and VSWR.

73,
Thor Hallen K5AGE


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