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As Part 15ers we strive to accomplish our mission within the rules. For me, it works, as I only expect to cover house and yard and this has been achieved. But I am very interested in those who are trying to reach a community, and these ideas are toward that objective.
It has been established that several Rangemaster AM 1000s can be spread around the neighborhood and operated in synchronization, but what a complicated undertaking that is. Theoretically a group of ten AM 1000s could be synchronized in one close-packed location and be either coupled together into a single 3-meter mast or a ten-conductor coaxial cable containing insulated wire which would allow separate vertical antennas for each transmitter, tightly grouped to achieve maximum phase agreement. Would 10X power from a single location cover a useful distance? If it did, this would no doubt be legal.
Home brew transmitters are another matter because one may only operate five of them and they cannot be synchronized. But, if one transmitter had 5-outputs, each driven from the same RF and modulation, would it count as one transmitter or five? Whichever, there would be a gain of 5X either into 10-separate verticals or coupled into a single vertical.
Total posts : 45366I haven’t read anything that says home built units can’t be syncronized – it would normally be hard to do, however.
I have read, in a variety of sources, that as far as the FCC is concerned we are operating “intentional radiators,” which are devices that emit radio waves on purpose rather than a device that also emits RF, like a desk top PC.
I think we are really limited to five intentional radiators, so even the multiple output approach would seem to run afoul of FCC enforcenment if the number of “outputs” exceeded five.
There is an interesting apporach outlined in one of our books in the Library that I feel is FCC compliant. This approach uses five intentional radiators and all five can keep DC input at 100 mW and be easily synchronized with no special construction techniques.
Read the information on this approach, using 100mW repeaters, here
Total posts : 45366Thank you scwis, the link on 100mW repeaters is very much on point. It seems I may have inadvertently described somewhat the same thing, but with a different way of arranging it in physical space. The “repeaters,” which I envisioned as “outputs,” look like a great way to enlarge a system within available rights-of-way while preserving the frequency established by the “master” transmitter.
Total posts : 45366you can run as many synced transmitters your budget will allow so long as they are type accepted.
but as bill blew found out you can’t run them within close proximity of each other or the fcc will cite you under composite rules.
i would say they need to be at least 1 wavelength apart to not be considered a composite setup.
putting them on the same tower though is certainly considered clustering by the fcc.
Total posts : 45366To find the official OET opinion about multiple Part 15 transmitters:
(1) log onto http://www.fcc.gov .
(2) At the top of the Home page, click on “E-Filing.”
(3) Cick on “OET Knowledge Data Base (OET).”
(4) Click on “Knowledge Data Base Search.”
(5) Type “708832” in the search space.
Total posts : 45366There are no specific regulations that address the use of multiple Part 15 transmitters. In 1987-1989, the Commission revised its rules for unlicensed operation (GEN Docket No. 87-389). In the original Notice of Proposed Rule Making, the Commission proposed to prohibit the use of multiple transmitters to extend coverage area. However, the final Report and Order in this proceeding did not adopt that prohibition. In paragraph 137, the Commission stated that it concurred with the comments that multiple devices should be permitted provided, the individual transmitters comply with the rules and any emission resulting from the simultaneous operation of the individual, non-coordinated transmitters complies with the rules.
but, when transmitters are placed on the same tower the FCC philly office will get you under composite rules.
they state it has something to do with class b compliance.
you would have to find out where wsjl / bill blew disappeared to and ask him for the details, but he was cited for having 5 rangemasters on the same tower.
maybe keith hamilton has more info on that situation.
Total posts : 45366On one hand, there appears to be no information of any kind regarding anyone being contacted by any office of the FCC in any state regarding the operation of multiple transmitters. A Google Advanced Search for Khz, Bill Blew, WSJL, Philadelphia, tower or rangemaster comes up empty.
There is also no reference to any low power transmitter needing to be certified in order to be used by an experimenter. The only reference to certification is in the context of sales, repeat – there is no reference for certification being required for the use of any experimental low power transmitter. Anywhere. Ever.
Furthermore no one has ever been cited for simply using a transmitter that is not certified. Ever.
There is also no reference for “composite set up” and no requirement for any metric referring to separation measured in wavelengths.
Per Google
Your search – “composite rules” site:http://www.fcc.gov – did not match any documents.
There is one result for multiple transmitters, having only to do with the health hazards of closely spaced high power RF emitters
http://www.fcc.gov/eb/FieldNotices/2003/DOC-252523A1.html
Any futher details would be most helpful.
Emil’s instructions take the user here:
Publication Number: 708832
Rule Parts: Publication Date: 04/05/2007
Keyword: Multiple, Low Powered Transmitters
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First Category: Radio Service Rules
Second Category: Part 15 General
Third Category:
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Question: Are multiple transmitters addressed in the Commission’s Part 15 Rules?
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Answer: There are no specific regulations that address the use of multiple Part 15 transmitters. In 1987-1989, the Commission revised its rules for unlicensed operation (GEN Docket No. 87-389). In the original Notice of Proposed Rule Making, the Commission proposed to prohibit the use of multiple transmitters to extend coverage area. However, the final Report and Order in this proceeding did not adopt that prohibition. In paragraph 137, the Commission stated that it concurred with the comments that multiple devices should be permitted provided, the individual transmitters comply with the rules and any emission resulting from the simultaneous operation of the individual, non-coordinated transmitters complies with the rules.
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Total posts : 45366I found the word “composite” used in 15.31(h), which deals with the testing of intentional radiators that have more than one radiating source. This is the only Composite Rule I found in Part 15. If there are other Composite Rules, I would expect them to be in Part 2.
Publication 708832 uses the term “non-coordinated,” which may mean “not composite.” So, it appears that multiple transmitters are allowed as long as they are not coordinated to act as a single (composite) transmitter. It would appear to me that any group of synchronized transmitters is “coordinated” or “composite.” The FCC seems to be arbitrarily drawing the line somewhere. They are allowing Radio Sandy Springs and WLOY, but not several Rangemasters on the same pole.
Total posts : 45366thats it. thats how they got bill b. of wsjl when he was running 5 rangemasters in synchronization on his tower.
thats why he started placing them around the jersey shore and was sending audio via uW stl.
Total posts : 45366I looked trough all of the sections related equipment authorization in Part 2 of the Rules, and did not find the words “composite” or “corellated ” in any of them. So, the only applicable rule I know about is Section 15.31(h). This rule relates to testing for certification.
The Rangemaster has not been tested or certified as a composite transmitter comprising several individual units. Also, it could not have been certified as a composite of several individual transmitters, because the limits of Part 15.219 would not have been met.
Total posts : 45366Sorry folks, but could someone please help me understand what the phrase in this quote from the FCC cite which states “the individual transmitters comply with the rules and any emission resulting from the simultaneous operation of the individual, non-coordinated transmitters complies with the rules. being “non-coordinated transmitters” means? What is a co-ordinated transmitter and how can I get one? This is just nuts!
Neil
Total posts : 45366From the way I see it (since this is not explained anywhere), a coordinated transmitter is one that is coupled, synchronized, or phase-locked with another transmitter for the purpose of combining its radiated power with that of another transmitter. This could involve keeping the transmitters in close proximity with each other to increase the radiated power in all directions, or maintaining a particular phase relationship between antennas in order to form a directional array.
It could be argued that simply providing the same program material to all of the transmitters is a form of coordination. However, dispersing the transmitters to various locations without attempting to form a directional array reduces the amount of coordination. Using simply frequency, rather than phase, synchronization reduces the amount of cooordination. Using different output frequencies for different transmitters reduces coordination further.
When Publication 708832 mentioned multiple transmitters to extend coverage area, it is obvious that all of the transmitters have the same program content (otherwise coverage area would not be extended at all). So, for sure, all of the transmitters are allowed to be coordinated by having the same audio input. Any additional amounts of coordination that are allowed are open to question.
Total posts : 45366Thanks, Ermi, for your take on this. You are probably correct. My “nuts” comment earlier refers to how a perfectly understandable sentence can be made vague by the inclusion of an undefined (at least in the context) word. Seems to happen a lot in the language of law.
Neil
Total posts : 45366All the comments made on this thread have been instructional and opened, at least in my mind, whole new ways of employing Part 15 AM. And this new idea grows out of it all:
Has anyone ever filled up ALL the open spots on your local dial with the same programming on all stations? In one’s immediate vicinity your programming would virtually blanket the dial while the feeble (hi power) stations would only have one spot apiece.
It would not increase the range but it would increase the odds that nearby listeners would find it.
It would also look impressive on the web page as if you were the BBC or some major conglomerate.
Total posts : 45366Carl,
I did something like this in my early “radio pioneer” days. My first transmitter was contained in a 78 RPM turntable which someone gave me because it didn’t have a speaker. They didn’t realize that it had a one tube line powered AM transmitter and sent a good signal several hundred feet with only a integral short wire antenna. I discovered that it produced a strong second harmonic so I carefully chose the operating frequency so the fundamental plus the second harmonic fell in the BC band on clear spots.
When I obtained my KnightKit broadcaster I was now on a third frequency. I didn’t do this for long because I was concerned about the higher harmonics from the “78” transmitter, but it was fun to know I could be heard on three different AM frequencies.
Neil
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