[Elecraft] BL-2 Connection To An Unbalanced Wire Antenna

[Don Wilhelm]

Ron,

I have been preaching similar points in ham circles for years now - and 
I find that many hams cannot visualize the difference between a 
"ground"  (meaning a return path for current) and Mother Earth.  
Actually any point where the RF current crosses the zero voltage point 
is a point of RF Ground (it is a potential, not a physical place), and 
on a balanced antenna it should occur midway between the two sides of 
the feedpoint - and a vertical with radials *is* a balanced antenna, 
that is why a balun is needed even on a vertical.

The English do distinguish between "earthing" and "grounding", and I do 
wish that sort of distinction were also in common use in the US, it 
certainly would help.

BTW - elevated radials *do* radiate in the very near field, but when 
arranged properly (pairs in opposing directions), the radiation is out 
of phase and will cancel at a distance from the antenna.  Your term 
"current sink" is not a description I would use.

73,
Don W3FPR

Ron D'Eau Claire wrote:
> Jim, IMX it's a mistake to equate "RF ground" with an Earth connection.
>
> An RF "ground" is just a low-impedance, low-reactance current sink for RF.
> Of course it is an integral part of the antenna circuit.
>
> An RF "ground" would not be expected to radiate, and most "counterpoise" or
> "radial" setups don't radiate a significant amount of energy*: 
>
> 1) Counterpoises near the Earth and on-ground "radials" tend to couple all
> their energy into the lossy dielectric of the Earth, never to be seen again.
> This is how BCB stations achieve a good RF ground generally using 120 0.2
> wavelength radials around their towers to couple the RF into the Earth. 
>
> 2) Elevated radials will radiate a lot unless they are carefully balanced
> and symmetrical so "legs" produce RF fields that cancel each other outside
> of the immediate area of the antenna. Such radials, like any RF ground,
> *are* part of the antenna circuit but, when properly designed, they are a
> non-radiating "current sink". In the common "ground plane" designs, they
> also decouple the radiating element from the feed line, providing an RF
> "ground" not only for the radiator but also grounding the feed line at the
> antenna so RF currents don't flow down the outside of the coax shield. 
>
> Ron AC7AC
>   
>