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“High SWR at the antenna input has few effects on the received signal for a configuration of a transmit antenna connected directly at/to the output connector of the transmitter. Those effects require a rather long transmission line between the transmitter and the antenna input, so that the reflected energy has undergone a significant r-f phase shift when arriving back at the transmitter.”
15.239 does not specify that a certified transmitter with a permanently attached antenna be used to comply with 15.239. The reference to a permanently attached antenna, or antenna with a special connector not common place in electronic supply stores only refers to units being tested for FCC certification and sold within the US. It does not mean that one must use a certified transmitter with a special antenna connector or permanently attached antenna to be compliant with 15.239.
15.239 also does not say a coax cannot be used. 15.239 does not say that a transmitter with more than 0.000011 nanowatts cannot be used.
15.239 does not specify anything other than 250uV at 3 meters of field strength from the transmit antenna. If someone can measure for that 250uV at 3 meters field strength from a system using an outdoor antenna system fed by a coax, there is no violation whatsoever, or worry about being in compliance.
Thus there are in fact some setups..like mine for example, that does use an outdoor antenna system being fed by 25 feet of RG-214 coax which is being fed drive from a Ramsey FM 100 (25mW TPO) through a 7 pole low pass filter, then into an attenuator box, adjusted so that the field strength from the antenna mounted 20 feet up measures about 270uV at 3 meters. And to put the icing on the cake, the inspecting agent was perfectly fine with it. The antenna is a turnstile C-Pol antenna built out of scrap TV rabbit ear whips, which isn’t very stable in the wind. I plan to rebuild it using 1/4 inch copper tubing and PVC pipe fittings..probably this summer sometime.
I do transmit in stereo as I don’t believe in transmitting mono audio in the 21st century..even on my AM 15.221 CC system, which transmits in C-QUAM AM stereo. Therefore I have the FM system very well built and tuned to prevent any return VSWR from mucking up that nice stereo sound. I don’t care that it fades out 300 feet down the street or that the stereo fades to mono a little before 300 feet, nor do I care that the stereo sub carrier occupies a little bandwidth.
If done properly, a C-Pol antenna, outdoor setup and use of a coax with appropriate power and if necessary, attenuation, is not “a bit cross purpose”. It is all in the spirit of building a system to be proud of and especially proud of when an inspecting field agent smiles and impressed by it’s compliance and use of recognized measuring equipment (Motorola R2012D) to ensure compliance.