Interesting Topic huh?
I think I know how they do it, but I don't want to spoil it for others.
they run leaky coax around the prison and feed it with this but 500mW is not nearly enough to properly feed a short run of leaky cable. on average it requires 2-3 watts to put a good signal within the building and radiate 250uV/m@3m away from the facility walls. i think with prisons their perimeter is actually considered part of the main building structure IE the yard and cell blocks are all considered part of a large building and the FCC treats the prison perimeter as if it was a structural wall for a building. i believe the distinction is made that prisons are a governemntal entity and not public or even semi public area where as a campground or apartment complex is a public / semi public area and a private entity. government gets a little more latitude as far as FCC rules than the general public does.
Those who make the rules tend to exempt themselves.
It is interesting that the view of the transmitter shows it is constructed with through hole parts. Most of the world has transitioned to surface mount which is less expensive. Perhaps they did not produce enough to justify tooling for surface mount.
Neil
Rated at 5 mW uses an antenna.
Yup 500mW would surely cover an entire prison if they use a rubber duck in the center of it. But leaky coax or carrier current FM would work far better. I still like Bill's take on how its 250 uV/M from the property line. With that in mind even a FM tx such as a 500mW one into a rubber duck could be legal if you put it in the center of the building.
... I still like Bill's take on how its 250 uV/M from the property line. With that in mind even a FM tx such as a 500mW one into a rubber duck could be legal if you put it in the center of the building. ...
Anyone may have a "take" on Part 15. But that doesn't necessarily mean that such a take was, is, or ever will be permitted by the FCC.
AFAIK, 47 CFR Part 15 has no provision either for campus broadcasting or leaky cable systems using the FM broadcast band, no matter where such systems might be installed/operated in geographic areas subject to FCC jurisdiction.
FCC §15.239 is the only Rule applying to unlicensed FM installations in 47 CFR Part 15, and it does not authorize either campus, or leaky cable operations.
Have a cracker, Polly
5 mW not 500
OK 5mW is just a bit more than the Whole House 3.0 puts out into a rubber duck. That makes more sense now. Nowever your signal is gonna be more than 1775 uV/M @ 3 meters. You would actually have to square root that to find out what 5mW would put into a rubber duck.
"You would actually have to square root that to find out what 5mW would put into a rubber duck."
I don't understand the theory behind this statement. What does the square root have to do with a rubber duck?
Neil
Confuded as well.
Get your rubber duckies in a row.
Enjoy
Chuckle Out Loud!
We started so seriously talking about prisons, and now we have soap suds and duckies.
Talk about quick rehab!