Total posts : 45366
I was only discussing the technical aspects of using an elevated antenna with an inductor in the ground lead, and not recommending its use. A high-Q choke coil would detune the transmitter so badly that the radiated power will be practically nil, and you will probably never attract the attention of the FCC. You would be better off using a 3-meter antenna at ground level. Neil’s comment above applies here.
The low-Q choke coil can work better than a 3-meter monopole above ground, but I think that its present use is based on a misunderstanding, and the choke coil does not do what it is advertised to do.
As for the variability of ferrites, this is not particularly relevant to the choke coil in the ground lead, since one coil would detune the transmitter as well as another; but it is a big problem for RF design in general. The only solution is to come up with a design that is insensitive to the variability. This is not easy, because there is no general approach. Another component that causes a lot of trouble in RF design because of its variability is the junction FET.
In response to an e-mail I received about this topic, I want to clarify that the the manufacturer that originally recommended using an inductor in the ground line recommends installing it at the transmitter ground terminal.