How would the FCC look at these things? There is even a patent-pending design for a self-resonant version (watch linewraps):
How would the FCC look at these things? There is even a patent-pending design for a self-resonant version (watch linewraps):
http://www.google.com/patents?id=yRgGAAAAEBAJ&printsec=drawing&zoom=4#v=onepage&q=&f=false
This antenna is not suitable for Part 15 AM, not becausw of FCC restrictions, but because a 3 m folded unipole will not work in the AM BCB if it is only 3 meters high. The folded unipole is a quarter-wave resonant antenna. The actual height at resonance is a lot lower than a quarter wave if the skirt diameter is very large, but this is only of interest for licensed broadcasting, not Part 15. The antenna just has to be too long for resonance. If the skirt diameter is 40% of the antenna height (which is HUGE), a height of about 0.1 wavelenth is required. 3 meters is a maximum of 0.017 wavelength in the AM BCB. A 3 m folded unipolepole in the AM BCB works much worse than an ordinary 3 m vertical rod above ground.
Thanks for the explanation, Ermi. I expected it wouldn't work ... similar to CFR antennas.
Ermi is correct in his analysis of the use of the folded unipole system. However, a short unipole can augment the efficiency of a short AM BCB antenna system and allow for a minimum of tuning components.
I have designed, built and licensed several AM BCB folded unipole antenna systems with demonstrated success. Some of the systems have been in use for almost 25 years. They are all based on a nearly quarter wave radiator. I suggest learning about this antenna system researched and developed by a graduate student at the U.S. Naval Academy.