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Howdy,
Here we go again. I was perusing the FCC document “UNDERSTANDING THE FCC REGULATIONS FOR LOW-POWER, NON-LICENSED TRANSMITTERS”
The radiated emmissions table section for AM BCB:
Howdy,
Here we go again. I was perusing the FCC document “UNDERSTANDING THE FCC REGULATIONS FOR LOW-POWER, NON-LICENSED TRANSMITTERS”
The radiated emmissions table section for AM BCB:
Frequency Field Strength Measurement Distance __(MHz)____________(microvolts/meter)______(meters)
0.490 – 1.705 24000/F(kHz) 30
1.705 – 30.0 30 30As can be seen, Field Strength between 0.490 – 1.705 Mhz is frequency dependent., e.g., @ 1.6 Mhz it would be 24000/1600 = 15uV/meter
But @ 1.705 Mhz and upwards to 30 Mhz, it’s a flat 30 uV/meter.
Am I wrong or doesn’t this actually allow MORE radiated energy at 1710 Khz? Now, looking ahead to 15.219(c):
“All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator’s antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.”
… I can’t see any other way to interpret this except as meaning we could be allowed up to 30 uV/meter at 1710 kHz if the antenna is hardwired to the transmitter output.
… or am I all wet? Comments please …
Total posts : 45366So dampness is probably your constant companion but your reading of the regs looks like it merits some consideration.
Most of us depend on the alternate rule described in Part 47 C.F.R. 15.219, which says that by operating in the band 510-1705 kHz with a total DC input power to the final RF output section that does not exceed 100 milliwatts and by using an antenna and ground connection that together do not exceed 3 Meters in length we are considered compliant without taking a field strength measurement.
This is also why there is sometimes some discussion about working in 1710 MHz – that freq was not included in the alternate rule for some reason.
When trying to decide for myself how I want to proceed with experimental broadcasting, I use a Google advanced search on the FCC Enforcement Bureau Field Notices site to see if there have been any enforcement actions against what I’m considering.
While I’ve never considered operating a 1 watt FM transmitter, if I went to the FCC site I would see lots and lots of enforcement for operators exceeding 250 uV/M limit, so I would decide to not do that 🙂
Total posts : 45366Here is an interesting thought: Say your 1 watt transmitter radiates ONLY on your property and not on the outer boundries. Naturally you would need lots of land so that the signal never made it off your property. What if any FCC action could or would be taken? Who would complain? No one could hear it off your land. There is no interference to licensed broadcast. Just a thought.
Total posts : 45366As can be seen, Field Strength between 0.490 – 1.705 Mhz is frequency dependent., e.g., @ 1.6 Mhz it would be 24000/1600 = 15uV/meter
But @ 1.705 Mhz and upwards to 30 Mhz, it’s a flat 30 uV/meter.
15uV @ 30 meters is about an S7
30uV @ 30 meters is about S8
Total posts : 45366As far as I know, the FCC regulates all spectrum and so the ownership of the ground under the spectrum isn’t a factor unless you are applying the educational consideration under part 15 for college campuses, etc.
The only way the FCC knows to check is if they get a complaint and if no one is there to receive the signal the liklihood of a complaint seems remote at best.
Strictly speaking I guess the FCC could still tell an operator to shut off a non-compliant transmitter even if it only covered private property, as the FCC owns the spectrum, even over your own property – but the chances of that happening sure seem nil.
Total posts : 45366Well in my mind the f.c.c really cant claim the spectrum.
I don’t see how they can claim they own something we can’t see, feel, taste or hear.
I don’t know, i have a hard time wrapping my head around this.
They can regulate it sure, but own it?
Total posts : 45366While I might agree with you in principle, the U.S. Congress feels otherwise, I guess.
“The FCC’s jurisdiction covers the fifty states, the District of Columbia, and all U.S. possessions.”
And, they charge rent (spectrum fees to commercial broadcasters), fine people for “trespassing” in the spectrum (NALs) and otherwise act like they own it.
Total posts : 45366This is paranoid curiosity, but what if the occasional plane or helicopter is “scanning” and trying to pick out questionable radiations? That would overstep the idea of “my property.” Besides the “public airwaves” having been taken prisoner, so have the sky spaces up above us for motorized flying machines.
Total posts : 45366What does S7 and S8 mean?
Total posts : 45366I suppose it comes under that sort of government thing. But the difference is safety, of course. A radio wave is not likely to crash through your roof and kill you 😉
OTOH, how can a government agency under the authority of an un-elected official auction off bandwidth they do not own, nor ever granted ownership by Congress, for $$? … But as I understand it, that’s what’s happening.
Total posts : 45366Signal level as measured on a receiver S-Meter. S9 = 50 uV. Each S- Unit represents a 6 dB difference. For example, S6 = 16dBuV, S7= 22dBuV, S8= 28dBuV and so on. dBuV can be converted to voltage received at the antenna terminals. So accordingly, S6= 6.3uV, S7=13uV and S8=25uV. Hope this helps.
Total posts : 45366To Ken Norris’ comment about selling off the public airwaves. Yes, if they can sell “our” airwaves without our approval, we should at least be credited with the appropriate amount against our taxes so that we at the very least are recognized as “owners” of the frequencies now in the hands of big money. Further, we should profit from the money generated by use of our public waves.
But no attempt is made to fool us because, frankly, we have “let it happen.”
Now that I’ve scolded us, let’s return to reality and remain content with our meager milliWatts and miniature antennas. Toys for inmates.
Total posts : 45366IMO, issues around radio that affect how we can and can’t operate, via a short rant about the policies involved with radio, is entirely appropriate, as long as it doesn’t escalate into something else.
I’ll try not to do that, though, unless I can offer a possible solution along with it.
E.g., I’m hopeful about the relaxed rules of the latest Low Power Community Radio Act allowing more stations to be birthed and grow. I wish it would also include AM, though. I think the LPAM group may have engineering documents from the first attempt to forge LPAM rules processing still around somewhere.
Total posts : 45366OK, thanks John … As I mentioned, I do know few things about audio engineering, but radio is relatively new for me.
Total posts : 45366The Communications Act of 1934 set forth that radio spectrum is considered a federal public trust and used for the safety and convenience of all the citizens of the United States. The act formed the Federal Communications Commission and set forth federal policy for the use of radio spectrum in the states, territories and protectorates of the U.S.
Since that time, regulation has been a concert of efforts from the Commission, Congress and the Courts. The F.C.C. has even been given the power to administer its own administrative court system and to make rulings on a case by case by basis.
As with any legal question, the time to consider it’s scope and consequences is before you embark into the area the regulations pertain to. In other words, If you don’t understand how it works, don’t play with it until you do.
And finally, in 1989 the F.C.C. passed through Congress an updated Communications Act that deals with updates in the realities of modern day radio communications and technology.
I would strongly suggest reading Parts 1, 73 and 15 of CFR 47. If your library doesn’t have a copy, they are available on-line and through the Government Printing Office. Like most legal texts, we must consider the regulations in the totality of all the F.C.C. rules and regulations.
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