It's not nitpicking...
Hi John!
Some of the principles desired in a power-system grounding scheme are also used for radio transmission and receiving, however, there are several more principles required for good/safe/proper TX/RX that power distribution and energy management have no concern.
In a power transmission/distribution/control system, safety is the first concern- electrical shock, fire prevention, and equipment protection. To keep a good system, having a good method of passing electrostatic discharge (from wool socks to direct lightning) through a path which will also provide for the above.
While it is usually unknown or misunderstood by electricians, inspectors, and even engineers, a good design of the power system and grounding should also minimize undesired electromagnetic and electrostatic emmissions. For example, a modern VFD driving a typical 3-phase motor may generate a varying frequency from say... 5hz through 120hz as it's intended design, but the switching action of the thyristors, the inductive and capacitive reactance of the load (the motor, wiring, snubber capacitors, inductors, etc) generates switching transients that are 3 and sometimes 4 orders-of-magnitude HIGHER. This coupled to long leads and improper grounding creates one awesome wideband HF radio transmitter. High-frequency arc-welders, and even just ordinary buzz-boxes also generate some incredible noise, which very easily gets fed backwards (through the power delivery system) into other equipment, and radiated into the ether.
For a radio receiver, this is a nightmare. No amount of input filtering will make the problem 'go away'... it may CUT DOWN the racket, but it'll take out a chunk of the good signal, too.
In cases where radio transmitting equipment is operating (especially broadcast), noise in the power system, as well as radiated EM energy, establishes enough of a presence in antenna and feedline structures to penetrate the transmitter's stages, mix with the transmitting signal, and generate some pretty awesome noise (transmit intermodulation) at the amplifier's output. If the amplifier is feeding through a bandpass filter, this out-of-band racket is basically absorbed by the filter, turned into heat. SOME of it will get through the filter, out to the antenna, and broadcast a LONG way.
In the realm of NON-radio tx/rx, this exact same racket can cause some screwy stuff in computers, remote-control systems, just about anything with microprocessors. A strong-enough signal will be interpreted as logic contrary to what exists, and an even-stronger signal will turn a chip into a fuse...
I'll say this (probably to the chagrin of many professionals), and it is true:
--There is no such thing as a 'good' ground. There's bad, and better.
--Grounding has characteristics. Like a wire conductor, the earth succombs to 'skin effect', and that effect has everything to do with resistance, inductance, and capacitance.
--AC grounding assumes 50 or 60hz AC.
--DC grounding assumes some relatively-fixed DC voltage.
--Lightning doesn't care what YOU think... there's a whole lotta DC there, and since you're parked inside a little VanDeGraaf generator, banging on a huge electromagnetic bell- you're gonna get AC at every possible frequency and amplitude, at least for a minute period of time.
--RF systems use common AC power, DC power, and considerably higher RF AC signals and power. The intention is to both transmit and receive AC signals that are typically substantially HIGHER than AC used in power systems. While they use the grounding system for AC and DC safety, fire protection, and equipment protection, they ALSO usually need to use the grounding system as a reference point (aka Counterpoise) for receiving and transmitting. The nature of this action is MUCH more demanding than the requirements of safety, fire protection, and equipment protection. An ordinary pair of grounding wires, connected per NEC code, using common techniques and bearing inspectors' approvals, can work fine in the power system, but very easily become a diode at RF frequencies.
--AC systems that generate garbage OUTSIDE of their regulated frequency shouldn't, but they do. An 'effective' grounding system (note that I didn't say 'perfect') will do a good job at quenching accidental, unavoidable garbage... and will also do a good job keeping RX/TX systems from being subjected to it.
[aside note- I've noticed that many wire tables and info now include 'skin effect' ratings. Generally, anything running at frequencies in the AC power distribution range experience very little propensity of 'skin effect', but I'm glad that they're starting to consider the effects of frequency on a conductor's capacity. Frankly, if you're delivering 60hz AC power through a wire, and skin effect is of great concern, you've got SOMETHING that isn't designed properly (there's noise on the line that shouldn't be there).]
Last, but not least- your question about counterpoise size versus radiating element.
Transmitting signals are either coupled as a balanced or unbalanced load. When using a ground as your counterpoise, you're transmitting into a radiating element AGAINST the ground, the transmitting load is UNBALANCED. In the case of balanced loads, you're transmitting against two radiating elements, neither of which is the ground.
Effective transmitting REQUIRES that your radiating element and it's counterpoise have a suitable resonant frequency, bandwidth, and impedance to match your transmitter and feedline. If ANY of those characteristics are incorrect, you'll have a mismatch, which equates to loss... heating on the feedline, antenna, or final amplifier, very high RF voltages (and low currents) appearing where they shouldn't, very high currents (and low voltages) where they shouldn't, and stuff smoking, burning, popping, etc.
In terms of a simple free-air dipole or ground-plane antenna, the counterpoise will have approximately the SAME 'rf length' (Xc/Xl predicate, and don't forget there's air adding capacitance). It is the combination of angle, surface, RF length, etc., that makes a basic 'ground plane' antenna an unbalanced transmit point that is within itself, a balanced load... it is a 'balun' by electromechanical design. The silly thing is... the antenna's counterpoise (in both balanced and unbalanced applications) is most effective at resonance... but in the world of good grounding, resonance is very undesireable- it's counterproductive... you don't want the earth-ground to oscillate, you want it to serve as an absorber.
In ANY event, a ground-referenced transmitting system will always be happy to have MORE counterpoise surface than less. Likewise, if you're running multiple bands (my system reaches from 400khz to over 10Ghz), there's never a concern about having too much ground-bonding or counterpoise area. By adding copper to the ground in long strips, all tied together, the resistance of the ground goes down, making it more effective.
Okay, did I break the forum? Everybody okay?
Dave Kamp, KW0D