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Well this is all nice and dandy but I don't quite get the point Rich, especially now suddenly with CC systems.
Are you trying to convince everyone that operating a CC system is only allowed on a campus?
WRONG!
Anyway I'm sure many appreciate the quoted sections out of the rule book. Probably some had no idea they were even there.
A 219 setup might be better, however history shows that those who have attempted an antenna setup on a campus found that even with the better field strength, that signal could not get through the buildings walls and was very difficult to control those field strength limits past the boundary of the campus. So in the end they discovered that going 219 was a waste of time and stuck with 221.
Reasonably so because these stations often operated 24/7 and skywave causes a problem at night on a college campus just as it does everywhere else. CC is not affected by skywave.
JFYI, my stations have been inspected twice, passed twice and will pass again. So relax, have a cup of joe or tall glass of favorite brewskey and realize that there are some of us out here who have all the necessary and recognized test gear to do our own measurements and be in compliance.
Thanks! 🙂
RFB
Appreciated your review, RFB, but my post was addressing a campus system using an intentional radiator, rather than carrier current.
Both types of systems are covered in different parts of §15.221.
Operating a system under the CC parts of §15.221 probably would produce even less field strength at most locations within the perimeter of that 5-acre plot than a system using the provisions of §15.221 for an intentional radiator.
Understood that CC systems can provide good service within one or more buildings, but their legal, radiated field strength is limited to a value that provides good service to consumer-level AM receivers only for fairly short distances (maybe 100 feet or so) from the a-c wiring of the building(s).
RE: A 219 setup might be better, however history shows that those who have attempted an antenna setup on a campus found that even with the better field strength, that signal could not get through the buildings walls and was very difficult to control those field strength limits past the boundary of the campus.
Just to note that there are no field strength limits for compliant, unlicensed systems operating under §15.219.
Quoting RFB: "Yet there are licensed stations violating rules left and right and no one seems to be concerned..especially the FCC."
If this truly is a problem for you, make a case against the stations you claim are in violation. Record their on-air signals after sunset, track their non-compliance with hourly IDs, EAS etc. Submit it as a formal complaint, backed with recorded evidence.
I once kept a Maryland AM'er held up in renewal proceedings for several months with a challenge I filed with the FCC. Since the Commission can't be everywhere, be their eyes and ears -- that's the only way they will take action.
"Just to note that there are no field strength limits for compliant, unlicensed systems operating under §15.219."
Absolutely true. However given the two most important specs in 219 call for a mere 3 meter antenna/coax/ground system fed by 100mW or less, pretty much puts a 219 systems field strength to a limit as well, though not spelled out in the writing.
Even with the increased allowance in field strength on a campus with an antenna, the signals were still too weak to be picked up reliably in buildings at the furthest parameters of the campus.
Worked well for the parking lots and outdoor areas. Some colleges did use a combination of 219 and 221. But there is no record of these free radiate systems being utilized on a regular basis like 221.
CC functions like that of a leaky coax system. And just like a leaky coax system, the signal, depending on frequency of operation, cannot exceed a certain amount of field strength at a specific distance. In the MW band, the limits are the same for a typical CC system feeding the power wires or one feeding a leaky coax. 157k/F 15uV/30m (47k/F 15uV/30m [meter formula]).
In the FM band it's 250uV/m @ 3 meters, be it from a wire, antenna or leaky coax or power wiring.
Now if my leaky coax or power wire runs 20 miles down road, my signal can travel along that length sending out a signal no greater than what is specified by the formula above for 221 FROM that wire or leaky coax. This is why the low section of the MW band is typically used because the rule and spec for 221 allows a greater distance from the wire or leaky coax.
You don't want to over drive a CC system for two simple reasons. One, obviously exceeding the 221 spec of 157k/F 15uV/30m. But the bigger reason is that you don't want to saturate radios close to the coupling point. Too much RF drive can cause hum, and cause inductive interference to other equipment like telco gear and cable and satellite distribution systems.
Here is some food for thought, from actual field tests and experiments.
Pushing 50 watts onto the power lines won't get you any increased far field range at all. The fact is this. Using actual commercially built coupling systems, even fed with 50 watts into that coupler, the maximum amount of high efficient coupling results in about 1 or 2 watts ERP off that power wiring. There is NO WAY that is going to throw ANY far field signal through power wiring running in metal conduits and stucco and brick and mortar.
In neutral coupling, same thing. A mere 1 or 2 watts ERP off that neutral line and that's with 50 watts being shoved into the coupler's input.
207 comes into play with maximum conducted RF energy back onto the power lines, which calls for 1000uV, which is MORE than enough to assure clear signal. In fact most CC systems never even approach that amount of RF injection. Most hit around 10 to 20 uV right at the coupling point for clear coverage of a typical large building. And extending that range to another building was done by installing more couplers fed by power splitters and repeater linear amps.
RFB
"If this truly is a problem for you, make a case against the stations you claim are in violation.:
No claim about it, they are in fact in violation. Anyone can look up the data.
And the FCC has PLENTY of evidence, documentation and recorded statements signed sealed and notarized. It was quite amusing seeing the field agent's expressions when informing and showing him how the ownership refused and continues to refuse to comply with the rules.
The time for more paperwork is over. It's time for the FCC to take action on what they have and start holding these licensed to violate stations accountable.
If they expect the public to obey the law, then they better start enforcing that law onto those who are granted a license under those same laws but violate them regardless.
Plain and simple. I nor anyone else does not need to do their leg work. They have no problem tracking down nanowatts and 10 foot long ground leads, but seem to have a major problem taking down licensed to violate offenders who have abused the public trust with the use of the public airwaves.
RFB
Read carefully, those two words look alike, but do not mean alike.
Another translation occurred in the past cheating us out of about 2-inches in antenna height.
At one time the rules allowed 10-foot vertical antennas for part 15 AM, but the federal potentates switched to metrics and rounded to the nearest whole number, leaving us with 3-meters. But there was no actual intention to shorten the actual legal length, it was just a kind of lazy short hand.
I am today adding 2-inches to each of my antennas.
Some day, sitting in jail, when asked "Why are you here?", I'll be able to say, "Two inches."
FWIW, a total radiating length of 120" rather than 118" for a base-fed, 1700 kHz vertical monopole with a 15-ohm coil loss and a 35-ohm r-f ground connection loss would add 0.15 dB to the radiated field. Probably not a sufficient motivation for a jail term :<)
"FWIW, a total radiating length of 120" rather than 118" for a base-fed, 1700 kHz vertical monopole with a 15-ohm coil loss and a 35-ohm r-f ground connection loss would add 0.15 dB to the radiated field. Probably not a sufficient motivation for a jail term :<)"
Any improvement, even a couple of inches on the radiator helps, just like adding more ground radials or extending them further out from the antenna, improving RF transfer efficiency to that system from the TX. It all adds up as they say.
I'm glad to read that post by Rich. There is a margin for error or margin for real world conditions or margin for a wee lil mo flea fling than the printed rule.
Wiggle room is what allows for experimentation and discovery. And is at the heart of this hobby and any sort of technical field or other.
To add a little correction in a previous post, most CC systems hit around 30 to 50 uV at the coupling point when adjusted for adequate clear signal, not 10 to 20. The 10 to 20 uV range is what a proper CC system will hit at it's 157k/F 15uV/30m point.
It's a good day indeed. 🙂
RFB
Part 15 is a franchise, a right granted to each individual by the federal god head.
Because every U.S. resident has a part 15 franchise, but the majority of the people don't use their's, I suggest that it would be possible to collect unused franchises by simple agreement between consenting parties.
For example, I would ring the doorbells at each home located 400-feet from my address, in a circular pattern at all degrees of the compass, and ask each person to sign over their franchise to me for 1640kHz, with the guarantee that if they ever decided to become a part 15 operator, we would help them find a different frequency.
Each time we collected a franchise we could add an additional 100mW to our RF final stage and another 3-meters to the antenna.
Having one central part 15 station would be the equivalent of having many separate part 15 stations.
There are no flaws in my franchise plan so I'm already making the rounds.