Mobile radio install, regardless of frequency..
Coax shield comes loose at the radio. No or poor range. RF is thrown everywhere inside the vehicle. Light bar goes off, siren goes nuts, lights in the dash flash, all kinds of crazy stuff. Retighten the connector at the radio, problems go away..
No earth ground involved. There is a d.c. path to the radio and antenna but that doesn't matter. We're dealing with RF..
A magnet mount antenna. No physical connection to ground at the antenna end but is coupled to body ground through capacitance. Same issues if the shield was removed at the source..
The coax is a circuit of its own and needs proper impedance at both ends to contain the RF inside of the shield. If this is achieved, the coax is just a pipe to send RF power to a radiator. The more that it is unbalanced, the more RF it emits from the shield.. (V.S.W.R.)
Well folks, when it's certified by the FCC and the vendor is telling you it's perfectly legal-it's no wonder it's all so confusing.
InfoSpot is a system built around the I A.M. transmitter/ATU. From the Infospot information:
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Technical Specifications
Transmitter
FCC certified.
Operating under FCC Rules Part 15, section 15.219.
Frequencies 530-1700 kHz, front panel selectable.
Antenna & Tuner
Adjustable tuner matches transmitter to antenna for maximum range.
Tuner housed in lockable weatherproof cabinet with threaded antenna mount.
3-meter whip antenna.
Tuner connection to transmitter – RG6 coaxial cable.
Coax maximum length – up to 300 feet.; 25 feet provided.
Antenna System
InfOspot is the only system of its kind to allow for separation of the transmitter and antenna/tuner by way of standard coaxial cable. This permits the antenna to be mounted in an optimum location for transmission, while the control cabinet containing the transmitter and digital message player remains conveniently located for control and maintenance. The gravity-mount roof stand with mats and mast is the most popular antenna mounting option.
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Seems they are implying placement of the antenna on the roof at the end of at least 25 feet of coax up to 300 feet.
So 12voltman, yes there are thousands of these in use and we have one high profile individual served an NOUO. And yes, properly terminated coax shouldn't radiate. He wasn't using coax.
And yes Rich, the bottom side of the antenna is connected to the coax shield so common mode current most likely will flow on the outside of the coax and radiate. And I suppose just because it's unintentional doesn't make it an un-intensional radiator. The FCC certified its use.
Rich himself said the FCC position on some of this is unknown and I don't see them addressing any of this other than to execute the rules as they interpret on a case by case judgement.
What was the question...
I have known many attorneys. One dear and wonderful woman attorney of my aquaintence served as an aid to a state judge. While he golfed and porked long lunches she was tasked with composing his opinions. She shared this as a way of confiding that you don't really know who writes laws and judgements. Whatever she wrote was probably good because she was good, but that's not always the case.
Many wordings in law are deliberately left open to interpretation. That provides a device by which inspectors and investigators can make their own decision about whether to find for or against a suspect.
FCC Rules Part 15 are not only pertained to RF devices, the language is loaded with legal devices so that users of the technology can be found innocent or guilty, based on the mood or special interest of the inspector.
The government does not exist to help individuals. It exists to flock them like chickens or other livestock.