Saturday, March 8, 2014

The 200 Foot Elephant

I was going to initiate this blog with a rundown of the Part 15 rules and regulations, seemed like the natural way to start it off... But really, anyone who actually might have interested in reading this blog, most certainly, already are quite versed on the subject.
So instead of trying to educate the educated, I'm just going to rant..

There's one thing that has always irked me; "The 200 foot rule"
If you google "Part 15 radio"  and on the very first search result is found a FCC guide entitled "Low Power Broadcast Stations".. Upon reading that page you will soon come across this notorious statement:

"Unlicensed operation on the AM and FM radio broadcast bands is permitted for some extremely low powered devices covered under Part 15 of the FCC's rules...
On the AM broadcast band, these devices are limited to an effective service range of approximately 200 feet (61 meters).  See 47 CFR Sections 15.207, 15.209, 15.219, and 15.221...

WTF??.. 200 foot?.. Who approximated that?

If you have a Part 15 AM radio station with a half mile or so listening range, then anyone who happens to read that statement would probably think you're a law breaking pirate.
It's on the FCC website, so it must be true..

Some refer to this as the "200 foot rule",
I like to call it the 200 foot elephant in the room. Everyone realizes what it says there, but ignores it, but not because their just turning a blind eye...

The fact is, it simply is not true, - at least not when it concerns the AM band operating under regulations defined in 15.219. So why then would it say that?.. One can only speculate. Most likely, it's a means of discouragement to keep  too many of these tiny stations from popping up all over the place

What first must be realized is that the “200 feet” reference is NOT a FCC regulation or rule. It is just came from an official who contributed a public statement in an attempt to clarify the actual rules for the sake of the common Joe..

The problem is that some of the wording in these types of notices and bulletins tend to at times get interpreted as being part of the rules.

The 200ft statement is just that, a general statement. The actual Part15 law applying to unlicensed use of the AM/FM broadcast bands is given in FCC paragraphs 15.209, 15.219 and 15.239, with some additional mention in 73.3550 (in reference to call letters).

But it's not a matter of what it says; the approximation is actually accurate when it comes to certain devices, but it's what it doesn't say, that makes it an untrue statement..

There are two primary governing options of part 15 in relation to this matter:

 ~ One is based on field strength only
    (ie; 200 foot) with no limits on power or antenna length. ( 15.209 )

 ~ The other is based solely on power and antenna length,
    but has no field strength limitations. ( 15.219 )

This alternative option is clearly outlined in Section 15.215: 
Additional provisions to the general radiated emission limitations.
(a) The regulations in §§ 15.217-15.257 provide alternatives to the general radiated emission limits
for intentional radiators operating in specified frequency bands.

This is why most part 15 broadcasters do not operate under 15.209, but use the AM band operating under the alternative rules of 15.219 as it has been provided by the FCC, because it specifically has no range limits applied to it:

§  15.219   Operation in the band 510-1705 kHz.

   (a) The total input power to the final radio frequency stage (exclusive
   of filament or heater power) shall not exceed 100 milliwatts.

   (b) The total length of the transmission line, antenna and ground lead
   (if used) shall not exceed 3 meters.

The 200 foot limit is not written into law, it is only an illustration cited in a public notice on the subject and states an estimated range, which by the way, particularly under 15.219, that approximate estimation is wholly inaccurate.

Blog Addum 2/5/2016: And to further emphasize the point, look up most any NOUO investigation that's ever been issued on an unlicensed AM broadcast, and you'll find this fact again confirmed in the FCC agents own reports.
What influences the agents to specifically acknowledge the alternate rule in their reports? It is because that is specifically what it tells them on page 4 of their official FCC field operations manual.. which states the following..
 "..There are two exceptions to this rule (15.219 and 15.221) and because there is no field strength limitation associated with operation under 15.219, an inspection is generally required to determine with absolute certainty that an AM broadcaster is in violation of Part 15..."

The 200 foot elephant has left the building...

Finally here's a quote from the Chief Engineer of the FCC John Reed concerning the above FCC Public Notice:
"..Yes, I know that a Public Notice was released saying that unlicensed AM and FM transmitters have 200 feet of range. On the practical side, however, you're lucky to even get 30 feet in the FM band. I did see one experiment achieve 400 feet of range when operated in a remote area with a low background noise level and no other FM stations any where near the selected frequency, using a very sensitive FM receiver with a good antenna, and transmitting in a mono mode with 75 kHz of deviation applied to the modulation.
This is why our rules do not specify a range - it's a relative term that is completely dependent on the environment. The same applies to range estimates for operation in the AM band. (That same Public Notice also incorrectly stated that you can have 50 mW ERP in the AM band and 10 uW in the FM band. The 250 uV/m at 3 m limit in the FM band translates to an ERP of 11.4 nW or 0.000,000,014 W. A field strength level of 24 uV/m at 30 m, as permitted under Section 15.209 at 1000 kHz, translates to an ERP of 10.5 nW. The non-technical author of the notice should have checked with the engineers before writing this. Note that the numbers in this Public Notice are not binding - the equipment must meet the standards in the actual regulations.).."

The 200 foot elephant has left the building, and he ain't coming back...

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