Topband: New Subject: 160M array feedline question

[Adrian]

Interesting page on the subject here ;

https://ham.stackexchange.com/questions/3675/what-is-the-effect-of-using-different-number-of-radials-with-ground-plane-antenn


On 23/3/21 1:55 pm, Guy Olinger K2AV wrote:
> A counterpoise is what we do when the full size of a double-ended 
> antenna, dipole, OCF, etc is too large for us to build, maintain, etc. 
> Very simply, we want to jam the energy from the shield of our coax 
> into the counterpoise, and the energy from the center conductor into 
> the radiating element, the vertical, T, inverted L, etc, the aerial 
> wire. Then we want to get all that energy back from the counterpoise, 
> none lost if possible, at the phase reversal. Any you don't get back 
> is mostly outright loss. With commercial high grade radials you can 
> show that the effective series resistance of the counterpoise is 1/2, 
> 1/3 or sometimes even 1/10 of an ohm. That means that the aerial wire 
> is radiating something like 50, 100 times the energy lost/radiated by 
> the radials' connection to ground.
>
> The two current destinations taken together MIMIC a circuit, because 
> the current into the counterpoise is the same, but opposite polarity 
> as the current into the radiating part of the antenna. If the currents 
> are equal and opposite, it looks like a circuit, walks like a circuit, 
> quacks like a circuit. You can model it with a fake circuit, and use 
> Maxwell's equations for circuits to predict what is gonna happen. 
> There is no magic circulation, just the ability to convince the coax 
> it is hooked up to a circuit. With the massive parallelism of a 
> commercial grade radial field, the radial's electrons are coupled into 
> the ground as a reservoir, with the push back from extra or missing 
> electrons that will return the current when the phase reverses. The 
> more radials, the more even the radials, the longer the radials, the 
> lower the power lost to current through resistive materials, lost to 
> dielectric loss in dielectric materials, lost to resistance in the 
> wire. Not perfect return, but a nice, high percentage return.
>
> In free space, it is possible to construct a counterpoise that NEC4 
> can accurately predict will radiate power to the far field at a rate 
> 30 dB below the RF current's energy. The essential loss is in the RF 
> resistance of the wire. You are talking about a counterpoise that is 
> 98 or 99+ percent efficient in free space.
>
> We are not interested in a counterpoise radiating, or invoking loss in 
> the environment. Talking to the counterpoise, I'm telling it I'm 
> giving it this pile of energy. A half cycle from now I want it all 
> back. No skimming off the top. Maybe just a skoch.
>
> A commercial quality radial field beneath a vertical is deliberately 
> intended to be non-radiating. Looking at the current around the base 
> of the vertical, the current to the east is exactly the opposite of 
> the current to the west, as are to the north and south, as are all 
> opposite radial pairs, therefore the fields generated are opposite, 
> intended to be net zero in the far field. That's on purpose, pretty 
> much true, and exactly what the engineers had in mind.
>
> It is easy to show that there are unfortunate ham designs and 
> implementations of the counterpoise/aerial concept where not even 10 
> percent of the power is radiated skyward. That is the 160 meter two 
> ton elephant in the room that gets ignored an awful lot of the time.
>
> 73, Guy K2AV
>