Total posts : 45366
Rich and others,
I agree with your “physical” science assessment of how a RF ground works. The Isotron is, by design, a tuned L-C tank circuit, resonating within itself. The characteristic impedance of the device over ground produces the propagated radio signal. Other hams have tested this antenna (transmit only) on wooden supports with ferrite line isolators and they work nearly the same as mounted on a metal pole or mast. I know that theoretically it shouldn’t, but in practice it does.
Also, just a note: I have engineered and constructed several licensed AM broadcast “Unipole” or folded monopole antennas that seem to work just fine over a non-existent or greatly diminished ground system. Theoretically, it shouldn’t, but in practice the measured field strength is significantly greater than a conventional 1/4 wave tower with NO change in the ground system itself. No real explanation why.
The FCC has gone around and around the proverbial scientific pole with broadcasters for decades regarding how to define the different “kinds” of grounds. Your explanation of the workings of the ground path is correct. However, I have no scientific reasoning to explain the operation of some operational radio antennas and associated ground systems, in reality or practice.
To confuse the issue even farther, the FCC, with the assistance of some creative engineers and expensive FCC attorneys, have bent the regulatory interpretation that there is a difference in RF ground, tuned-ground, service ground, safety ground, EMP ground and lightning ground systems. They are all grounds, but according to “accepted” engineering practice, (FCC terminology) they are all different even though they may be intergrated into the same system. Sometimes, FCC rulings get muddled in legal, political and government process and physical science loses out. That is where the term, in broadcast enginering compliance, was authored, “wiggle room”.
Rev. Marshall Johnson, Sr.
Senior Pastor, President
Rhema Christian Fellowship, Inc.
Rhema Radio – The Word In Worship
AM 1660 – FM 93.5