Carrier Current radio technology is described and regulated in various sections of the Part 15 FCC Rules, and there are various ways that carrier current is used, but this morning I conducted a search specifically to determine the frequency spectrum within which carrier current operates.
Carrier current rules describe applications spanning a range from 9kHz to 30mHz.
There is no mention of carrier current above 30mHz.
However, I would think that FM transmission by carrier current would fall under 15.239 Operation in the band 88 to 108mHz, where any type of antenna is allowed, the one restriction being the field strength. Thus using the electric lines as the antenna would be the intentional radiator of choice, and the signal strength would be the deciding factor as to whether is is legal.
'you shouldnt' and 'you cant' are the best ways to get me to do something i think i want to do.
when the manteca station was on the air, and when we were "scrutinized" by our friends, the carrier current unit i ran was checked and deemed ok. the entire rig was hand built for me.. soooo.. im gonna go with "its ok"
also; not a lawyer.
I'm glad you're going to go ahead with the CC plan, mir.
Anyway, I'm enjoying this side-trip into the murkier part of the rules, which nobody seems to know exactly.
If the Greek-mitter has 50-ohms output it should match fine into a coupler.
Now I'm interprepting the rules to say that it's o.k. to build your own, but that's different from a "marketed" unit, which I think is where the FCC has a control-hold.
Since my old LPB unit is right now broken, and I do want a back up even after it's fixed, I am going to explore building one.
This whole learning process is kind of fun... home school college, sort of.
I'd really be interested in a home brew coupler...
Way back before I discovered the AMT3000 and this website, I'm guessing in the 1980s sometime, I built an AM 2-stage transmitter from a schematic in a book. It had a tuning-slug in the coil and no modulation circuit, but it made a carrier.
The book of circuits shows some CC coupler sketches, not very well developed, but I started to make a coupler even to the point of winding wire onto some kind of a form. But I really did not know too much, having last worked with RF decades ago with tubes and just enough knowledge to get into trouble.
These professional couplers from Radio Systems and LPB are very nicely designed to cover a range of conditions. Not possible to achieve with simple home-made experiments.
rich,
carrier current fm, is the same rules as it is with free radiate (antenna) or leaky coax (100 miliwatts with 250 microvolts per metre at 3 metres, as it always has been)
i know this becuase i have talked to the fcc agents near dallas about it, plus they were checking every part 15 out in north texas one day a couple of years ago, and they told me that i was okay, ive been doing ccfm since i started part 15 5 1/2 years ago alot of people dont really do ccfm for many reasons why, which is why i asked the agents.
they were okay with it, i wasn't interfearing with anybody my transmitter power is less than 20 miliwatts field strength is legal when they checked it and haven't changed anything since then. so.
so long story short, its legal and okay, the rules and regulations on part 15 fm is still the same.
hope this answers your question.
Carl Blare: "However, I would think that FM transmission by carrier current would fall under 15.239 Operation in the band 88 to 108mHz, where any type
of antenna is allowed, the one restriction being the field strength. Thus using the electric lines as the antenna would be the intentional radiator of choice,
and the signal strength would be the deciding factor as to whether is is legal."
Andrew Bentley: "carrier current fm, is the same rules as it is with free radiate (antenna) or leaky coax (100 miliwatts with 250 microvolts per metre at 3 metres, as it always has been) etc"
The FCC specifically authorizes carrier current operations for the AM broadcast band (§15.221), but not for the FM broadcast band.
Assumptions about the legal use of FM carrier current systems always can be made.
Andrew, the FCC does not specify 100 milliwatts (or any other power) for an unlicensed FM transmitter -- only that the field intensity three meters in any direction from its transmit antenna cannot exceed 250 µV/m.
Just how practical is running 88.1 to 107.9 as CC?
On the subject of carrier current above 30mHz, I have located the applicable section of the Part 15 rules.
15.209 Radiated emission limits (e) carrier current systems... at frequencies above 30mHz the limits in paragraph (a), (b), or (g) of this section, as appropriate, apply...
(a) ... the field strength of radiated emissions (88-216mHz) from unintentional radiators at a distance of 3 meters shall not exceed 150mV/meter.
(b) and (g) apply to digital devices.
(a) ... the field strength of radiated emissions (88-216mHz) from unintentional radiators at a distance of 3 meters shall not exceed 150mV/meter.
The unit of measure in this FCC Rule is microvolts/meter (µV/m), not mV/m as shown in the clip above. The unit mV/m means millivolts/meter.
Note that the correct limit applying to this clip is 100 µV/m less than allowed by FCC §15.239 for unlicensed stations in the FM broadcast band.
Also the correct SI unit for megahertz (millions of hertz) is MHz. The term mHz means millihertz (thousandths of a hertz).
The Rules can be confusing, especially when the wrong units of measure are quoted 🙂
really? i was told 250 mv/m or maybe it was 150 mv/m.
rich where did you find it at, and i'll look at it, cause i was told something different, or maybe they told me what you said, i just want to double check land make sure and if what your telling me is the case, ill make the necessary corrections. so there wont any be any issues...
thanks for your input...
The m and M and u and milli and micro are always difficult for me to express correctly, so the above needs a few fixes to represent what the FCC has published.
However, my MAIN point still comes across, and that is to point out that carrier current above 30mHz, uh, MHz, IS IN FACT addressed in rule.
Previously it was questioned whether the FCC recognized carrier current in the FM region.
The lower permissable radiation level applies when the FM range of frequencies are injected as an unintentional radiational device, where radiation is not intended.
If radiation is intended using a carrier current FM system 15.239 can be applied.
ABMedia 1: "i was told 250 mv/m or maybe it was 150 mv/m. rich where did you find it at, and i'll look at it, cause i was told something different,..."
The reference was given in Carl's post #24: FCC §15.209 (a).
BTW the correct unit of measure in that reference is microvolts/meter (µV/m), not millivolts/meter (mV/m).
However, my MAIN point ... carrier current above 30mHz, uh, MHz, IS IN FACT addressed in rule.
FCC §15.209(a) addresses intentional radiators used in various parts of the radio spectrum, and states (bold font added for this post):
"(a) Except as provided elsewhere in this subpart, the emissions from an intentional radiator shall not exceed the field strength levels specified in the following table:" (omitted)
FCC §15.239 in the same subpart of the Rules containing §15.209 is an exception permitted by the words in §15.209a, as it permits a field of 250 µV/m at three meters, rather than 150 µV/m.
However the only place in Part 15 where unlicensed carrier current/leaky cable transmission is specifically authorized occurs in §15.221, and only for certain systems using the AM broadcast band.
IF this statement by Rich were true...
"However the only place in Part 15 where unlicensed carrier current/leaky cable transmission is specifically authorized occurs in §15.221, and only for certain systems using the AM broadcast band."
THEN all other parts of the Part 15 application of intended or unintended radiant devices using carrier current devices WOULD REQUIRE A LICENSE.
YET, there is no place found where such a license requirement is stated, EVEN THOUGH the use of such equipment IS DESCRIBED.
PERHAPS Rich can tell us about the license requirement section of the Part 15 carrier current regulations?