[TowerTalk] optimum vertical length

[jimlux]

jim Jarvis wrote:
> Jim,
".
> 
> Regardless of the electrical length of the antenna, though,  getting  
> it up high and in the clear
> is the important factor.   A 40m vertical dipole plays amazingly well  
> on multiple bands, with
> a tuner, if you can get the high current portion of the antenna up  
> 50' or so, in a tree.
> 



So, then, what about this trade-space (again, in the world of fairly 
inconspicuous antennas)..

You could have a ground mounted vertical (of whatever length)

OR

a shorter vertical sticking up from the roofline, with a bunch of wire 
as a counterpoise/ground screen on the roof.  (or a vertical dipole)

If one uses the old CB antenna rules of 12-15 ft max height above 
structure as a constraint, are you better off with some sort of short 
vertical dipole, up 30 ft on the roof, or with a 45 ft vertical, on the 
ground?


Assuming you're not at the beach, etc.  It seems that getting the 
feedpoint up in the air will reduce near field losses from the soil, at 
the expense of incurring losses in your groundplane/lower half of the 
antenna.