Carl, While looking for other things, I stumbled across this little FCC study which happens to have some relativity to your topic at hand.
Below is pasted a slightly compressed version of the original full text found at http://transition.fcc.gov/ftp/Reports/rpts4002.txt
I found this document by the way, within the "Collected Engineering Documents"
from the Audio Division, Media Bureau - under the category 'AM Expanded Band (1610 to 1700 kHz)' This same category also provides other documents in reference to radio interference.
I don't know if you find an answer to your (a)(b) conundrum there but if you want to explore further, take a look around: http://transition.fcc.gov/mb/audio/decdoc/engrser.html#AMEXBAND1
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TELEPHONE INTERFERENCE SURVEY
May 2, 1994
Prepared by
Field Operations Bureau
Federal Communications Commission
The Federal Communications Commission (FCC) receives 25,000
complaints per year from individuals who are unable to use their
telephones because nearby radio stations interfere with the proper
operation of the telephones. Whenever the radio stations are on
the air, the telephones pick up the stations' transmissions which
then override any ongoing telephone conversation.
For about three years field offices have submitted narrative
reports indicating that interference to telephones is an increasing
problem among consumers. Because of those reports, FOB began a
detailed sampling of calls and letters. The sampling is an actual
count of specific complaints and inquiries, conducted one week
each month by all offices. This sample is the basis of our count
of 25,000 telephone interference complaints per year and is the
most accurate measure of compliant categories now available.
The FCC's Field Operations Bureau (FOB) has done an informal survey
to obtain information about telephone interference such as:
-which telephones are affected
-what type transmitting stations are involved
-the power levels at which the stations were transmitting
-whether commonly available filters would be effective in
eliminating the interference
-whether specially designed telephones would be effective in
eliminating the interference
Procedure
Thirty-five FCC field offices across the country participated in
the survey. Each office was to choose three recent complaints of
telephone interference on a random basis, and then to investigate
the complaints.
At the transmitting station FOB staff would determine the type of
station (i.e., amateur, citizens band, broadcast, etc.), measure
the station power, and obtain information on antenna height,
antenna gain, and distance from the complainant.
Types of Transmitting Stations
FOB inspected 108 transmitting stations which were involved in the
telephone interference complaints, as follows:
Citizens Band . . . . . . 47
Amateur . . . . . . . . . 27
AM Broadcast . . . . . . . 23
FM Broadcast . . . . . . . 10
International Broadcast . 1
Types of Telephones
FOB tested 241 telephones found in the complainants' residences. Of
the 241 telephones 68 percent received interference. Attachment 2
lists the telephones tested. FOB did not observe interference on
32 percent of the telephones it tested. These telephones are
listed in Attachment 3.
Types of Filters
FOB tested the effectiveness of the AT&T Z100B1 filter on 138
telephones receiving interference. After connecting the filter to the
telephones, 62 percent of the telephones continued to receive
interference. The filter did eliminate interference on 38 percent of
the telephones. A number of other filters were also tested on 82
telephones receiving interference. As a group these filters
eliminated interference on 29 percent of the telephones. They did not
eliminate interference on 71 percent of the telephones. Attachment 4
lists the filters which eliminated the interference.
"Interference Free" Telephones
FOB tested "interference free" telephones at 52 locations where the
individuals were receiving interference to their telephones. The
"interference free" telephones eliminated interference at 96 percent
of the locations.
Conclusions
The transmitting stations most likely to cause telephone interference
are citizens band, amateur, and broadcast stations. Citizens band
stations accounted for half the telephone interference cases. Amateur
stations and broadcast stations accounted for the other half.
The power levels used by the radio transmitting station did not appear
to be a significant factor in causing telephone interference. Power
levels of 10 watts or less caused telephone interference in a third of
the cases.
A large portion of the residential telephones appeared to be
susceptible to interference from nearby radio transmitting stations.
Although some telephones did not receive interference, the limited
nature of the testing performed in conjunction with this survey would
not support the conclusion that they would always reject interference.
Filters cannot be relied upon to eliminate telephone interference: in
two out of three cases in the test sample, they did not work.
Manufacturers can, however, design telephones to be interference-free.
The "interference free" telephones were immune from interference
virtually all of the time.
A Final Note
Notwithstanding the 25,000 reports of telephone interference the FCC
receives annually, it is FOB's experience that, as large as this
number is, it probably represents only a fraction of the actual
instances in which this interference occurs. Given the enormous
numbers of instances in which this type of interference is experienced
by consumers, it is our hope that this survey, notwithstanding its
informality, will serve as a catalyst for affected parties to
productively address and resolve this problem. As always, FOB remains
ready to assist in that effort.Mon Feb 14 1994
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Complete text at http://transition.fcc.gov/ftp/Reports/rpts4002.txt
But as RFB says; Don't dig so deep you cant get out!
"But as RFB says; Don't dig so deep you cant get out!"
Maybe person (b) can run interference for person (a) before that happens! 😀
RFB
heh, heh..
Splendid work, splendid!
The FOB seems to have the problem fobbed off on them.
Don't you think the telephone interference problem should be solved by the phone company and radio stations?
Maybe the FCC would like to come over here and solve some of my problems.
They could do your lawn and perhaps light hauling.
It's good work though, really, inspecting things outside the office. Plenty of secretary's phone numbers to go around.
Ok so after all that, does (a) and (b) make more sense now?
Has anything changed in the issue of interference and what the FCC does not do about it?
First things first...get rid of the notion that government is there to solve all our problems. Do that and then you can clear A LOT of confusion.
Second, it never was the FCC's responsibility to solve interference problems. The FCC's job is to regulate the radio spectrum and issue licenses and new rules. Even when doing inspections of interference, they cannot solve them, only recommend to whomever is causing the interference to do something different. It is not up to an inspecting agent to declare judgement or make orders on site.
In short, it's up to you to solve it, by changing frequencies, re-orienting the antenna, discussing the issue with the other party, work it out. And the FCC will tell you that if you call them, they prefer folks handle their own pitty party problems. They have bigger fish to fry.
The only quick fix your gonna find to solve everything with
interference is to simply ban everything.
So start shutting down stuff and boxing it up and tossing it all out the window. Then there will be no more interference.
:/
RFB
Sure is a lot of info in this thread, it's going to take me some more time to sift thru it.
But, I also don't see a conundrum, but, yes, it could become one depending on how you choose to operate.
This isn't rocket science, in fact, not much science at all. I'm sure the FCC has dealt with this thousands of times, yet the rule remains. Why?
Because it's so simple. For our purposes, Part 15 radio cannot cause and must accept interference to/from other radio. It simply means you have to broadcast on an empty frequency, and not bother your neighbors, reception or otherwise.
I do not want to cause interference nor will I ever cause interference but I think if I'm not allowed to cause interference, no one should be allowed to cause it.
The rule (b), saying we must accept interference, is the same as saying that someone else is allowed to cause the interference that I must accept. Well, that's not fair. If I can't cause interference they shouldn't be able to either. I want them stopped.
On another thread RFB said
"Every radio receiver made has to be certified under the Part 15 rules since they use and generate radio frequency energy within. Thus they have to comply with our two favorite (a) and (b) people.....
..(a) this device must not cause harmful interference.
..(b) this device must accept any interference including interference that may cause undesired operation."
AHA! This gives us Conundrum No. 2! (b) (paraphrased version) ALL RADIO LISTENERS MUST ACCEPT INTERFERENCE.
Well then NOBODY has grounds for complaining about interference but NOBODY may cause interference.
Am I getting through to anybody?
Why do I get kicked out of every sports bar on Tybee Island?
Oops. That last part was my imagination.
The (a) and (b) are really two different things and MEAN two different things.
For example. A transmitter rarely receives interference..but must not cause interference. (a)
A receiver rarely transmits interference, but must accept interference to be compliant. (b)
Either way you slice the pie, your subject to both.
Now let's get down to the nit grit dirt here. Even receivers filled with zinc plated loose tolerance valves and canisters had incredible sensitivity and filtering to prevent them from generating interference. But since they do contain oscillator circuits which generate RF energy, they have to comply to (a). Their high quality also helps prevent receiving interference by design. Who wants to buy a crappy radio receiver? And unless intentional, interference is extremely rare under normal circumstances of operation.
So (b) in this case, and in others too, rarely shows its ugly face anyway. So why fret over irrelevant nth decimal point pointless points? Your only driving yourself insane trying to squeeze blood out of that non-existing turnip.
RFB
I smell a turnip.
A turnip??
Oh oh oh.. I had to read RFBs reply again.. you smell the turnip that he is telling you doesn't exist.. I get it now.
Well Carl, you've heard of "phantom itch"?? - It's when amputees feel an itch on a limb that does not even exist.. It drives them nuts!
Their hand itches, but they don't even have an arm.. It's an itch they can't scratch because it's not really there.
I too suspect that (a)(b) is just your phantom itch.
Superregenerative receivers! You used to be able to hear other RECEIVERS from 1/4 mile away when you were trying to hear radio stations! Maybe that's when the FCC worded that part of Pt. 15!
I don't think ANY superregen set could have complied! (I'm showing my age here again....anybody else ever have one of those noisy monsters?)
"I smell a turnip."
Well I smell Collard Greens cooking in the kitchen, a lot of fireworks going off for the pre New Year Blast Bring-In thing they do here..(yes even in the 8* freezing weather), enjoying a Root Beer and TSA banned cupcake plotting the next major incursion to bring about a new era for Part 15.
Who's with me? :p
RFB
Carl, while reading the following document I couldn't help but to repeatedly keep thinking about your INTERFERENCE saga. So I compiled a few choice excerpts - well, actually it's kind of long, but much shorter than the whole paper, and a worthy read:
(by the way rlkocher, I've never heard of those supergenenertavive receivers, but I'm sure I will end up doing a little searching out of curiosity!)
Ok, now for some interference from...
Unlicensed and Unshackled: A Joint OSP-OET White Paper on Unlicensed Devices and Their Regulatory Issues
Unlicensed wireless devices are products that are permitted to emit radio frequency (RF) energy, but require no specific device or user authorization, either through registration or grant of a license.
This area of communications has become a province of continuous change....
>>>On Page 4:
It is generally easier to explain unlicensed devices in terms of what they are not, rather than what they are. To that end, let’s first
explore the primary characteristics of licensed devices and services..
In order to prevent harmful interference, the Federal Communications Commission (FCC) grants licenses to operators permitting them to broadcast at a particular power level, at a specified location, and in an assigned frequency band. These licenses are normally exclusive with respect to all of these dimensions, and they last for a finite period of time. The licensee can expect to be free from harmful interference which will disrupt the normal operation within the licensed service area. The amount of protection granted to licensees varies from service to service.
In contrast, unlicensed devices have no exclusivity even in the bands within which they are authorized to operate. Part 15 of the FCC rules permits the operation of authorized low power radio frequency (RF)devices without a license from the Commission. The technical standards contained in Part 15 are designed to ensure that there is a low probability that these unlicensed devices will cause harmful interference to other users of the radio spectrum. Part 15 intentional radiators, i.e., radio transmitters, are permitted to operate under a set of general emission limits or under provisions that allow higher emission levels in certain frequency bands....
In exchange for operating on an interference sufferance basis, unlicensed devices are free from the burden of the normal delays associated with the licensing process and, as a bonus, spectrum use is free of charge.
In the end, consumers reap the benefit of lower costs, less hassle (no need for a license to operate the device), and more rapid development cycles. Because they are free from the delays inherent in the licensing process, unlicensed devices can frequently be designed to fill a unique need and be introduced into the marketplace rather quickly. The availability of spectrum for use by unlicensed devices has spawned a variety of new applications...
>>>On Page 7:
In the late 1980’s, as technology made possible the introduction of devices designed to operate at higher frequencies than the rules had to date contemplated, the general field strength limit was again becoming too restrictive. In response to petitions for rule making, the FCC completed an omnibus revision of its technical and administrative provisions for the operation of Part 15 devices. In this rulemaking, the FCC standardized the emission limits in various bands and established a number of general usage frequency bands placing limits on peak emissions.
This revision also gave structure to the Part 15 rules which, until that time, had been revised on an ad hoc basis each time a new device was introduced. First, the revision re-classified unlicensed devices...
Intentional Radiators are devices that intentionally generate and emit RF energy by radiation or induction.
Second, the revision created general categories that allow intentional radiators to operate at very low powers in any band except where expressly prohibited. Greater emissions were permitted in certain bands where the FCC deemed such operation would not result in production of harmful interference. After this re-write, the FCC continued to modify the Part 15 rules in a more orderly fashion as advances in technology dictated.
>>>Also of note, that I want to throw in, while not actually referring to our broadcast frequencies, on page 9 there is reference to the use of multiple transmitters:
2. Current Issues
70-80-90 GHz. In an effort to anticipate future needs, the FCC has underway a proceeding in which it seeks to promote the commercial development of spectrum in the 71-76 GHz, 81-86GHz and 92-95 GHz bands. Specifically, the Notice proposed to make the 92-95 GHz band
available for unlicensed use and suggested rules for unlicensed operation in that band...
The FCC is reviewing comments filed in response to its proposal. Potential uses of this spectrum may include high- speed wireless local area networks, broadband access systems for the Internet, and point-to-point or point-to-multipoint communications systems. These
applications are especially well suited for higher frequencies primarily because, as noted earlier, transmissions on frequencies this high travel for shorter distances, making it possible to locate several transmitters in close proximity with less risk of receiving or producing harmful interference.
>>>And more concerning interference on pages 10 and 11 a couple interesting quotes:
2. Adopt quantitative standards to provide interference protection: interference temperature. The Task Force recommended the creation of a quantitative standard for acceptable interference that provides both greater certainty for licensees and greater access to unused spectrum for unlicensed operators.
On of the most notable of the Task Force’s recommendations, from an unlicensed device perspective, is that it urges the adoption of an “interference temperature.” The new metric would allow the FCC to quantify and manage interference on a band-by-band basis, by establishing limits on the noise environment in which receivers would be required to operate. To the extent, however, that the interference temperature in a particular band is not reached, the report argues,
users who emit energy below that temperature could operate more flexibly – with the interference temperature serving as the maximum cap on the potential RF energy any device could introduce into the band.
>>>>And lastly, still on interference.. On Page 45:
B. Interference Concerns for Unlicensed Devices
At the heart of all spectrum concerns lies the question of interference. A certain amount of interference between devices is acceptable; however, beyond a certain limit interference can be considered harmful and, unless locally correctable, may require some form of external intervention. The Task Force recognized that a better construct for this limit would prove advantageous for unlicensed devices.
Interference which may be intolerable in one service might be perfectly acceptable in another. In essence, interference imposes a cost for the user who must protect himself, but for certain lowcost
unlicensed devices, the burden imposed by interference may be considered trivial. For example, while interference that causes excessive break-ups or dropped calls would be considered unacceptable by the average cell phone user, a walkie-talkie user, who pays only a
pittance for the device and pays no monthly fees, may be willing to accept that interference.
Another analogy is that of the automobile. The system of roads in the United States is open to common access by all. However, since not every driver can use the road at once, some drivers may be required to wait in line sometimes. In densely populated areas such as cities and at times like rush hour, the road system becomes so congested that users experience delays. In contrast, in more rural areas there are fewer cars and thus less congestion. All drivers intuitively understand that when traveling in a city at rush hour, one is likely to experience traffic. Similarly, users of unlicensed spectrum may grudgingly be willing to tolerate “rush hour” congestion in densely populated areas or times when usage is high.
This congestion is one economic means of rationing the resource when it becomes scare... An ever- increasing fraction of today’s radio applications have ranges measured in yards rather than miles. As radio ranges become smaller, more devices can be used in any given area without ill-effect. As usage patterns evolve, a better definition of what constitutes interference may be necessary. In refining such a definition, a compromise may not fit all users in all areas. In more densely populated areas, spectrum users may be expected to tolerate some congestion before it is considered harmful interference. At the same time, because congestion may not be a problem in rural areas, it would be unfair to impose the same restrictions for rural users that city users incur.....
The interference temperature, if implemented by the Commission, can be complemented by the use of radio devices that have a certain amount of built- in “smarts.” For example, unlicensed devices could employ frequency agile, intelligent radios capable of identifying unused or
underused spectrum, adjust their power level, or in real time bid for the exclusive right to broadcast before emitting any RF energy into the band. In this way, the interference temperature in any particular geographical area emission band could be dynamically self- regulated by the spectrum users. However, this concept has its detractors.
Because unlicensed devices derive much of their benefit from being inexpensive, small, and designed for a particular use, one could
argue that including such smart technology will add significant cost, thereby reducing the attractiveness to consumers....
The above makes the point that the introduction of interference temperature as a concept must be handled carefully. The Spectrum Policy Task Force concedes that studying the feasibility of
implementing interference temperature would be time-consuming and expensive. However, it believes that the benefits of undertaking the task would be well worth the effort expended.
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By the way, while this document that I selected these exceprts from was referenced with a link from the FCC website - the link was bad and I had to find it elsewhere, I found it here: http://www.doc-txt.com/Unlicensed-and-Unshackled-A-Joint-OET-OSP-White-Paper-on.pdf