Total posts : 45366
The article you and others have cited is for a “licensed” radio service called Information Service Radio which is operated by government entities and agencies (not Part 15). This design, when used for a Part 15 ground system, will likely exceed current FCC rulings and cause NOUO’s. The 3-meter rule would, specifically for the Rangemaster, not allow for what would be a ground radial system and ground lead in excess of the maximum length (3-meters).
The transmitter and antenna are very nearly at the maximum already. Even tech tips on the Rangemaster web site recommend a ground radial system. However, in the last few months, an additional recommendation by Hamilton of adding a filter device to the ground lead to reduce the signal. Two different versions of the filter have been developed and available for sale. In the case of KENC, the FCC tech lab tested the device with findings that the filter didn’t reduce the additional radiation sufficiently to warrant keeping the transmitter on the air. The FCC ordered two transmitters out of three to be shut off. The SStran doesn’t seem to have the same issues with the FCC inspectors.
You mention resonance. Resonance is a technical term that means when a radio frequency circuit possesses zero reactance. That further means that the capacitive and inductive reactance cancel each other out, leaving just the pure resistance of the load, or radiation resistance. Because ten foot radials are so short, in comparison to the length needed to resonate, their efficiency is very low. However, even with a very low efficiency, the more short radials there are (to a point) the greater the signal launch from the antenna. If the intrinsic ground conductivity of the area is very low, the signal beyond several hundred feet will be poor no matter how extensive the ground system is. The amount of power radiated by a real world Part 15 antenna is realistically in the single digit nano-watt range under average conditions. And finally, resonance is NOT impedance matching the transmitter output to the antenna feed point. Matching simply brings the individual impedance values closer to each other for the purpose of better energy transfer from one to the other.
The effect of a good ground radial system for the Rangemaster transmitter (from my own experience) is a very solid near-filed signal (within several hundred feet), improved audio quality, higher modulation with less distortion and sharper, more defined peak tuning.
“…ground radials are a waste of time, pointless, and of no benefit.” Nothing could be further from the truth. In Part 15 broadcasting with a Rangemaster transmitter, there is a balance each operator must find between what the FCC requires to be legal and what improvements can be made to have a useful community-wide AM signal. Recent history has demonstrated that a good faith effort on the part of the station/transmitter operator may not be enough to keep it on the air. So, I am forever optimistic about the future of low and micro power unlicensed operation, balanced by the presence of the FCC and the ever present possibility of the NOUO.
My mention of the gauge or thickness of the wire used is merely to assist in not spending a pile of money on copper wire that simply isn’t necessary. By using the minimum gauge of wire, you save money and get the job done safely. Copper is very expensive at today’s prices. You ever wonder why radio station transmitter sites are vandalized and the copper is taken? It’s expensive.
I have built very extensive grounding systems for 100 kilowatt FM and 50 kilowatt AM stations where there is a lot of stray electricity. A good ground system is for more than just getting the signal out there. Why “over build” a ground system for one tenth of a watt?