Question:

Hello Keith,
I have a question on Rangemaster ground wire length and Part 15 operation.
If the transmitter is located on a rooftop and the ground wire goes directly to an 8 foot stake at the side of the building, the combined antenna
 and ground lead length will exceed 3 meters. Is the transmitter power then reduced accordingly below
100 milliwatts to the max. field strength level? Or am I misunderstanding the interpretation of Part 15?

Answer:

Hi,
Part 15 is a vague murky world… I could talk for hours about it. If all part 15’s were held to the strictest interpretation, then we would have z
to pull tabletop indoor part 15’s outside and mount them on the dirt, and people would have to take
other extreme impractical measures with the 100’s of thousands of units that are already out there.

Generally I think what happens is transmitters are operated in the manner in which they were designed to operate. For example, an indoor Part 15
table top would use the house electrical system for it’s ground, (which strictly could be included in the 3 meter limit) but since the unit was certified
 that way, then there is an apparent allowance for the unit to operate that way. Also it is a matter that that house wiring system it is connected to is
 a negligible radiator and apparently is not included in the 3 meter limit . See this link to show how a typical tabletop transmitter is grounded

In our case the unit is designed to be a rooftop or pole mounted device, suggested mounting and grounding examples were demonstrated in the manual
 and were carefully gone over together between ourselves and the FCC. This information was to be in the manual as a condition of certification. The lightning
 safety protection is very important as is the safety grounding to allow the protection to work. Also the tuning and power
 set information. All this information was gone over and is part of the approval package.

I hope all that  is helpful.

Something else, in your question you are assuming that the entire ground connectivity is included in the "ground lead" The definition I have understood
from the FCC generally pertaining to all Part 15 transmitters is that the "ground lead" is the short length of wire that connects the transmitter to the local ground.
 What the local ground is isn't clearly defined. It does seem clear that the FCC does not want the local ground, what ever it is, to radiate.

For example look at this link This indoor transmitter connects it's radio ground directly thru to the house wiring, so you could wonder if the house wiring
was part of the "ground lead". Since the house wiring is an obvious poor radiator, is not designed to be a radiator, and just plain doesn't
 radiate, but serves as a "safety ground" then it doesn't seem the house wiring would be included in the 3 meter limit.

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