Tom's argument about l/c energy storage networks would result in misleading ammeter readings, I.e. Are those amps going somewhere or just circulating back and forth? "Regular" radials would have the current on the meter "going somewhere" (real power that does work, in this case the "work" would be radiating a field). An energy storage network, such as Tom mentioned regarding a coil, would have circulating currents that don't "go anywhere". Circulating currents are reactive power and have associated losses and heating of wiring but reactive power does no actual work. Just using an rf ammeter wouldn't distinguish between the two.
While I'm more familiar with this kind of measurement in power systems (where it's related to power factor), you have to measure the current *and* voltage and derive meaning from the phase angle. Basically you need both magnitude and phase measurements to be able to figure out what is going on in such a system. You could make these measurements with a scope using a voltage probe and current probe on different input channels. As soon as you have ac running in non-linear systems (anything more complex than a pure resistive load), all the measurements become a lot more interesting. It's also a lot easier to make measurement errors or get confused by obscure inaccuracies in test equipment (rms vs. Non-rms ac voltmeters are a classic example of this). -Bill [Sent using Blackberry Messaging] ----- Original Message ----- From: [email protected] <[email protected]> To: topband <[email protected]> Sent: Wed Aug 01 23:41:33 2012 Subject: Topband: Fw: FCP model Very interesting discussion. Can't we quantify our ground systems by placing RF ammeters at the feed point? It would seem to me that once the current in the ground wire - whether it be attached to a ground stake, ground radials, elevated counterpoise, resonant radials or whatever - is equal to the radiator current no further improvement is possible. ----- Forwarded Message ----- From: Tom W8JI <[email protected]> To: topband reflector <[email protected]> Sent: Thursday, August 2, 2012 5:57 AM Subject: Re: Topband: FCP model Let me throw this out for comments. I think I found a valid test for the theory the FCP does not radiate, and thus does not have ground loss. My countering statement was it cannot be a counterpoise, and cannot have current, without E and H fields. Even if we null farfield radiation (which is an electromagnetic field, as opposed to E and H induction fields near the conductor) we still must have local fields, or current will not flow out along the conductor. Counterpoises only work because they have fields. I modeled an FCP with enough spacing to not violate segment rules. I made two FCP's at right angles, with one foot spacing, 90 degrees from each other. I connected them at the normal feed terminal to form a "dipole" of sorts, using one as the counterpoise for the other. I used lossless wire in the model. Resistance at the current maximum in freespace is 0.03 ohms. This very low resistance indicates very deep cancellation of farfield radiation. Efficiency was 99.2 percent. This indicates a very small model error of some type (probably because of close spacing between wires or failure to align segments) , because it should be 100%. I moved the wires over real earth at 45 feet height. Resistance now changed to 0.04 ohms and efficiency changed to 20 percent. This indicates nearfields are impinging on lossy soil, because that is the only source of loss beyond the initial 0.8% error. I moved the wires to 10 feet, and current maximum feed resistance increased to 1 ohm. Efficiency was then 0.4%. This indicates severe ground losses. Now the points of this are: 1.) 10 feet is too close to the "soil" used in this model. Elevated radials at 10 ft are not going to be good if soil acts like the model. 2.) 45 feet could be high enough to be reasonably isolated from wire E and H fields in this model. 3.) Cancelling radiation is the farfield has very little to do with local E and H field levels that cause loss. 4.) We can't make local fields go away or it will no longer be a counterpoise. Those are the fields that allow current to flow out on the open ended conductors. For example, nylon rope would be a good non-radiating counterpoise with no local E or H fields, unless we rub a furry cat along the rope. 5.) We reduce ground loss by spreading the fields out as evenly as possible over the largest possible area of lossy media. What we should not conclude is that fields are distributed the same when an antenna is connected. They are not. The E field in particular will move toward the antenna open end. (That's why we should put counterpoises below the flattop wires, so fields are less intense on lossy earth. When I was 12 or 13, I knew to put a counterpoise below the flattop wire. :-) This test does not quantify losses. It does not quantify anything. It only shows trends. It shows relatively intense E and H fields surround the wires, even though someone 20 miles away might not hear the radiation field. I think a test like this shows the difference between EM radiation, electric induction, and magnetic induction fields. 73 Tom _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
