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

[olinger at bellsouth.net]

  I gave up on using "ground" for anything other than ground rods and lightning protection. For antennas where only one connection radiates to significant degree I refer to a "current sink" as the device one uses to accept the current from the opposite side of the feedline. This allows me to construct a sentence such as:  "If you use a ground rod as a current sink for your all-band vertical, you can lose 10 db or more to losses in the dirt."

I can also have the discussion about whether the current sink contains more than one thinks, or whether part of what you consider to be the current sink is in fact radiating, and therefore receiving as well.

As to "RF ground", that term is so polluted and spread over so many fairly independent issues in common use, with some having vociferous emotional attachments to their favorite of the various meanings, I've given up. Even with specific intention to NOT step on feelings and stir up old controversies, the technical point gets lost in the resurrected hollering and confusion from honestly-held differing definitions. 

The issue with RF in the shack is whether while transmitting one set of cabling in the shack has a disruptive RF voltage when measured against another set of cabling in the shack. While some techniques work decently often, I'm not aware of a silver bullet technique, as even point-of-entry grounding can sometimes have miscellaneous impedances which defeat the intent at RF.

73, Guy.

-------------- Original message ----------------------
From: Don Wilhelm <w3fpr at embarqmail.com>
>
> 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
> >   
> >
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