[TowerTalk] Feedline (choke) question

[David Gilbert]

I already did with the example of a floating portable setup. Current 
requires an E-field to push it.  You could connect a grounded wire to a 
point on the coax shield and it wouldn't shunt any common mode current 
to ground because there is no E-field (voltage) for it.

An earth ground is a grounding point for lightning strikes because the 
current that flows in lightning is the result of charge buildup (an 
E-field) between clouds and ground.

Earth ground affects transmitted RF because the radiated RF impinges on 
the earth and is absorbed and reflected, the ratio between the two being 
affected by the parameters of the earth (conductivity and permittivity).

There is no such E-field between the coax and the earth due to the 
common mode current on the coax shield.  Even if you view the earth as 
some sort of super large capacitor, it would require an E-field to push 
current into it.

The earth is NOT an RF sink.

Dave   AB7E



On 9/27/2025 12:55 PM, Brian Beezley wrote:
> "That's a fallacy.  It simply isn't."
>
> Dave, it would be helpful if you'd supply your reasoning.
>
> In many ways I regard ground as just another conductor. However, 
> unlike a wire, it is normally without resonance effects. That's the 
> "current sink" aspect. Current will flow from a wire into ground if 
> you make a connection. If you're using a ground rod, the impedance at 
> the connection depends on the rod length, rod diameter, and the 
> characteristics of the soil. If the soil is uniform, reflections don't 
> occur, unlike for a wire of finite length. The current dissipates as 
> it spreads within the ground, which acts like an infinitely long wire 
> with a traveling wave. However, when ground strata are distinct and 
> well defined, resonance can occur. An example shown for the stratified 
> ground calculator described in the writeup below exhibits strong 
> resonance. A water table 200 feet below a desert surface magnifies 
> surface ground conductivity by a factor of 10, which is pretty 
> amazing. I think such situations are rare because I suspect most 
> variation in ground characteristics occurs gradually rather than as 
> distinct strata, which is necessary for resonance.
>
> https://k6sti.neocities.org/sg
>
> Brian
>
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