The G0ICC 'Wondercoil'
has been used successfully over the years and has given surprising results.
On one occasion the antenna connection broke and the wondercoil and the earth
served as an effective radiator of RF until the problem was discovered. SWR
did not give any clues because it appeared normal!
The wondercoil works on 160 and 80m because it provides 50 Ohms at around 2 MHz and about 100 Ohms at 4 MHz so whatever you put on the end will, at varying degrees of efficiency, radiate due to the match at the end of the feeder and the mutual relationship due to the bifilar wound nature of the coil - ie it matches as well to earth as it does to whatever is above it.
It will also work as a balun, again due to the phase relationship, for dipoles. Due to the harmonic relationship that the 'classic', rather than the WARC bands, have it has also been known to work on higher HF frequencies.
The most typical application though is for space saving as loading coils for verticals, longwire antennas and �shortened� antennae where the mismatches and potential for RF flying around from the feeder and everywhere else in the case of the G5RV is deemed undesirable.
The �Wondercoil� does not replace the ideal case of a full size and correctly
positioned antenna; however, not everyone can accommodate these due to densely
populated areas yielding postage stamp sized back yards! If you make and use
one of these, why not let Richard G0ICC
know how you got on?