Marv, since when is 20 MHz ( 88 MHz to 108 MHZ ) considered "narrowband" ??? There is NO antenna made that will offer a linear gain curve for that wide of a bandwidth. One could build a design with a low Q ( maximum bandwidth but with lower overall gain ) and tune it for the middle of the band or "peak it" for maximum gain at one end of the band or the other.
As to your comments about "dedicated" FM antennas increasing the selectivity and rejecting out of band signals to a greater extent than "broadband" TV antennas, that IS a falsehood. An antenna that was specifically resonated for FM would also be HIGHLY susceptible to amplifying the 4th harmonic that was originally generated within the CB band. Since hundreds if not thousands of watts are in use on that band with little to no filtering in the amplifiers, high level 4th order harmonics ARE a reality. As such, a higher gain antenna at that frequency could actually INCREASE out of band interference and its susceptability to such things. That is, UNLESS the antenna was highly directional and pointed right at the FM transmitter and the offending CB'er was not in the pathway.
This is not to mention that many earlier cordless phones, baby monitors, etc... are transmitting around 49 MHz. As such, their second harmonic is occuring pretty much smack dab within the FM range.
With those things in mind, optimum performance for anyone that is located at distance from the majority of transmitters would be realized with a large directional yagi array on a rotor mounted as high as possible. Since the majority of citizens don't want to deal with something like that, simply installing SOME type of antenna on one's roof or in the attic would do wonders compared to an indoor wire dipole or rabbit ears. As to the "specialized" FM designs like the Fanfare and Magnum antennas, they are both base loaded designs. Anyone that works with RF knows that base loading is pretty low in efficiency. The main benefit of this design is that it offers less wind load and is not quite as ugly as a top or center load. Nonetheless, this design should offer pretty reasonable performance as long as they are vertically oriented and mounted out in the open. The use of a tuned counterpoise underneath them would also benefit them quite a bit.
Simply using the "homebrew" center fed dipole mounted vertically that i detailed how to build in a previous post might also solve a LOT of reception problems for less than $5. Sean
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