The following quote is from section 15.211 of the FCC OET63 bulletin ~Understanding The FCC Part 15 Regulations for Low Power, Non-Licensed Transmitters – http://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf
Tunnel radio systems
Many tunnels have naturally surrounding earth and/or water that attenuates radio waves. Transmitters that are operated inside these tunnels are not subject to any radiation limits inside the tunnel. Instead, the signals they produce must meet the Part 15 general radiated emmission limits on the outside of the tunnel, including it’s openings. They also must comply with the conducted emission limits on the electric power lines outside of the tunnel.
Ok, I get it.. no I don’t.
Now, let’s just stop here for a minute… and just in case your thinking that I’m quoting this portion of the FCC bulletin as a means of leading up to some kind of wonderful loophole we could utilize somehow or something… I’m not. Nor is this an attempt at pointing out some important or usefull information.
No, It just struck me odd, and I’m curious why the FCC made it a point to specify such permision to lift the radiated limits for Part 15 in a tunnel to begin with?
For what reason did they feel a need to bring this subject at all? Why??
To me, it just seems weird.
But even weirder, and kind of funny to me, is what they say in the next paragraph..
Buildings and other structures that are not surrounded by earth or water (e.g oil storage tanks) are not tunnels. Transmitters that are operated inside such structures are subject to the same standards as transmitters operated in a open area.
Well thank you very much for letting me know, becuase I thought they were tunnels, and was just getting ready to start broadcasting inside of an empty oil storage tank till you told me that.
Is it just me??.. Why would they ever even say such a thing!
There has got to be some kind of story behind it all.
And I really wanted to transmit in that oil tank too.
Rich Vein of FCC Ore
One loophole I see in this interesting FCC document, is that if it really means a lot to someone to be able to play with 50kW transmitters, what we need is a tunnel (meeting the earth and water specs).
The section on buildings not being tunnels is foggy, since buildings attenuate signals to varying degrees and the federal inspection measurements would be made outside the buildings in the case of private residences.
But we must realize that writing reasonable explanations of complex topics is most likely a slap-dash composition task between alcohol lunch and happy hour at five.
Frankly, my house is a tunnel because of the stucco screening which is almost an anechoic chamber.
Perhaps it would make sense for part 15 stations to draft a “Rule Interpretation Handbook” in which we could express what we think the rules are. In a way, some of us already do that here at part15.us.
You made me google anechoic
You made me google anechoic chamber.
It said buildings not surrounded by earth or water.. but didn’t metion fog.
You know, if they ever build a hadron collider in the US, maybe you could get a job there, then could legally broadcast 18 miles under part 15
My Car
I drive a 2007 Hadron Collider. It has good AM radio.
More To Say
It seems to us that a structure of RAMMED EARTH would qualify as a tunnel since such walls consist of highly compacted earth, such construc tion commonly found in low humidity desert regions, such as the south-western U.S.
FURTHUR, we envision a wall designed as a water-storage container so as to collect rain run-off for water recycling and conservation, idea copyright 2014 by Carl Blare.
A house built of water-filled walls would like-wise meet the tunnel designation.
Matter of fact the above ground long ground leads made possible by such specialized walls would be a further benefit for Part 15 evolution.