Inverse square law really only pertains to an omni directional point source. If you focus the energy it doesn't directly apply anymore. Since we are not using a true omni directional antenna, the inverse square law doesn't really apply.
Greg_E wrote: "Inverse square law really only pertains to an omni directional point source. If you focus the energy it doesn't directly apply anymore."
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Hi Greg,
A directional transmit antenna pattern radiates more power in some directions than others, but that does nothing to change the propagation characteristics of whatever that radiation may be.
So when describing the power density radiated by an antenna with any radiation pattern (isotropic or directional) -- the inverse square law still applies. The key point here though is that the inverse square law does not apply to field strength in any case.
Going back to the equation for the field strength from a 1/2-wave dipole that I posted earlier, the only variables in it apply to the radiated power and the path distance. The equation shows that for all radiated powers over the short propagation paths of Part 15 AM systems, field strength changes are inversely proportional to distance from the radiator, not inversely to that distance squared.
Rich
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I just wonder what will pass an inspection anymore,I read so many different things,I'm afraid I dont know what to believe.Check out this discusion at:
http://groups.msn.com/GospelRadio/part15goodnews.msnw
Tower mounted and radial systems,Oh MY! What is one to think???
Put it up,keep my nose clean and pray not to get the "knock"?
Or be happy with my 200 feet of coverage?
And ,unless I am mistaken,it is illegal to use a fake callsign? I see so many write ups with them I dont know what is legal or not. The rules state you may id,but not with anything that resembles a commission authorized call sign. I dont see any enforcement actions for that.
Regards,Lee
My enforcement action was in 1997, NOUO for an FM operation.
I was using KFIR (Friendly Information Radio, K-fir, the tree!) and one of the paragraphs of the NOUO was focused specifically on using license-like calls.
The problem, from the FCC's perspective, is that using license-like calls implies licensing and implies that the call user might be entitled to things they are not entitled to, like concert tickets, music CDs, press passes, etc.
I personally believe content very much a part of the unofficial enforcement picture. Licensed stations pay spectrum fees to the federal government to broadcast. A sort of payment for the use of the airwaves. I personally believe this creates the impression in the minds of the licensees of ownership of the spectrum and that spills over into ownership of listeners. In my opinion this results in demands for enforcement when a licensee feels threatened.
If your content is engaging and informative a licensee WILL feel threatened, and will feel that you are accessing HIS listeners and demand enforcement.
The problem that creates is that if a field officer doesn't shut the station down, the licensee is calling his congressman and screaming that the FCC isn't doing their job.
Another reason I use NOAA weather radio for content 🙂
and that I recommend against using anything that's remotely like a licensed call.
Hence SCWIS 🙂
Experimental broadcasting for a better tomorrow!
Here is the rule on that:
Users of nonlicensed, low-power
devices operating under part 15 of this
chapter may use whatever identification
is currently desired, so long as
propriety is observed and no confusion
results with a station for which the
FCC issues a license.
47 CFR 73.3550(l):
Earlier Rich wrote:
Note that r-f power can be conducted from one place to another via a coaxial cable with its shield grounded, and still radiate essentially none of that power directly via that coax. This is the common configuration for AM, FM and TV broadcast antenna systems, where the tx is in a building near the tower(s), yet the r-f power entering the coax also appears at its termination (less I^2R loss in the coax), where it is radiated by the antenna.
That is obvious, the point I was trying to make is that from an extreme interpretation of Part 15 (b) that no ground could exist except for dirt. I also just meant that there would be some radiation from the coax shield even if it was a good power transfer system.
I are not in the business of interpreting FCC law, I just recommend that people follow the law and cooperate with the FCC. Contact the FCC for law interpretation. I may try to let people know what other customers have done successfully, and what other agents have passed, but in no way am I purporting breaking any law. six foot pole, ten foot, twenty foot, fifty foot, who knows? Only the FCC agent that comes calling and how HE chooses to interpret the law, nobody else.
I think scwis is right, a lot of enforcement is driven by broadcasters. If a Part 15’er isn’t getting rating points in his town, then I would think local broadcasters would not consider him competition.
The good thing like I have said before is that if you do get a visit from the FCC, I have found that without fail they are good guys, they will work with you to find a solution and will cut you a break when they can. I have never heard of one of our units being shut down, if an agent sees something he doesn’t like typically he will give you a paper detailing out how to correct the issue, and typically allow you to operate until he returns to approve your changes.
Regarding scwis's statement:
"The problem, from the FCC's perspective, is that using license-like calls implies licensing and implies that the call user might be entitled to things they are not entitled to, like concert tickets, music CDs, press passes, etc."
Well, technically that wouldn't be an official problem unless they felt you were representing yourself as a licensee and as such it possibly constituted fraud. But even if you're very clear about being pat15 and explain how short your range is (in the case of FM definitely), some bands still may offer CDs of their music because *any* station that will play them can look good listed in the promo pack they use for getting gigs. There are also other ways to get press passes, for example if you're a reporter who writes articles regularly for a church or other group's newsletter then that group may elect to provide you with ID that qualifies as a press pass and might even be labelled as such. But if one is trying to do basically "social engineering" and claiming to be from Wxxx or Kxxx and talking as if it's a radio station in the usual licensed sense? Then it could qualify as misrepresentation at the least. Conspicuous use of something that closely resembles call letter for licensed BCB might be somewhat misleading. But so far as I know, music CDs from bands wanting any exposure they can get and to be able to say they're getting airplay somewhere, press access, and being passed into concerts or other events can all be done legitimately and honestly and are not something a part 15 might not be "entitled to" as much as anyone from a licensed station.
The concern I would have with using Kxxx or Wxxx type identifiers are that even if they aren't in use when you start using them, how would you know when/if a license *was* issued for them? You could start using them when they're unassigned and then be surprised a couple years down the road when you get shut down or fined for unauthorized use of a call sign belonging (now) to a station a thousand miles away. Or even if you did somehow keep up on things like that, you could be using them for a few years and suddenly have to come up with something else when they get assigned and etc. Say you also had a website, stationary for correspondence, and a newsletter going that all used that identifier or promoted your station. You'd have to change it on all of those as well as dealing with the resulting confusion.
Now so far as the Talking House and its ATU.. I think the point is that it was approved as a unit apparently both with and without the external ATU. There is nothing in part15 that says the FCC can't approve a manufactured unit that doesn't happen to fit all of the conditions of 15.219(b). That TH is very tight-lipped about the use of the ATU and they apparently will only give user support to those who buy the equipment they sell directly from tham may be more than just paranoic sales practices, it may be part of the agreements that allow them to market the TH with or without the ATU. For example they may have promised the FCC they wouldn't sell their ATU except for use with their own units and that they would discourage its use with any other transmitter. So it's very possible that it is legal when used with a TH, but wouldn't be legal hooked up to gear from another manufacturer since that combination was never approved.
Just my thoughts on the matters.
Daniel
I have been re-broadcasting a local FM station on my AM transmitter for test purposes. From what has been said here, I would assume this is a no-no. If I broadcast some music, then I would likely be in violation of copyright rules. What should I use as a test source - suggestions?
Gerry
What I'd suggest Gerry, is go HERE and look for things in genres you like that fall into a creative commons category that fits your station/transmissions and what sort of use you're making of it. Like some allow commercial use, some
are only noncommercial, etc. You can find an explanation of those HERE .
Some of it is def "not ready for primetime" (in my opinion), some is quite good. Depends on your tastes and etc. But it's sound more interesting to listen to than a test tone, for sure. It's at least a fairly easy place to start with finding material for broadcast that is allowed and where the owner of the copyright is allowing it to be used without RIAA and etc royalties.
Bon apetit
Daniel
You could rebroadcast the weather, either the NWS broadcast or the Canadian equivilent. That should work well for testing.
Frank
www.easthillradio.com
Daniel and Frank - thanks for the info.
Gerry
It's public domain, it's interesting and informative and includes a time check, and it REALLY sticks out on the dial so you can clearly tell where your signal (and your harmonics) are showing up.
Experimental broadcasting for a better tomorrow!
I know that this thread is five years old, but I also know what the issue was on this case.
I believe that this transmitter was reported by a licensed broadcast station. If my memory of this is correct, then it would have been reported after the broadcast station located the "Part 15" station and measured their signal.
The broadcast station would have then reported the "Part 15" station, not because of the quality or content of the "Part 15" stations broadcast, but after measuring the "Part 15's" signal strength, it was determined that the "Part 15" station signal was exceeding the allowed transmit power as measured near by the antenna (where ever that measurement may have been).
Now I do not remember the end results of the case investigation, but there was considerable conversations in the office as to why this "Part 15" station (as well as other transmitters in use by the manufacturer of this "Part 15" station) was exceeding "Part 15" emission limit regulations. Agent Dombrowski even had conversations with the FCC engineer that wrote the "Part 15" rule.
The consensus, in the Langhorne FCC office (technically the Philadelphia FCC Office), was that the ground wire leading up the the antenna was also radiating the signal of the broadcast station, as was the antenna. It was believed that the ground wire had in effect become part of the radiating antenna.
This caused the "Part 15" transmitters signal to exceed the authorized "Part 15" emission level and thus was considered to be an unauthorized, unlicensed broadcast station.
there is/was much much more to this story than just a licensed station reporting this guy.
i was directly involved with this and the guy is friend of nearly 10 years now.
i came in and readjusted and remounted his tx to make it legal. he now gets out better than when it was on the mast and is now legal.
"there is/was much much more to this story"
What is interesting is the certification and how it was set up. If that TX was certified while mounted 20 feet up on a pole, then why do all other certified units get tested on a table 1 meter off the floor? And that certification data is available for reviewing, while certain others are not..along with the field handbook.
And it's no surprise the operator got better range with the TX mounted near the ground. The system is working like it should, and mounted accordingly like the big licensed stations. We don't see 420 foot towers suspended 20 or 100 feet in the air! We don't see their feed point at the top of the tower or anywhere else other than at the base. At most the base of the tower sitting on a cement slab might be 3 to 5 feet above the dirt.
Imagine taking a dipole antenna and putting the top element 20 feet in the air, and your ground element at the floor. Won't work very well will it!
Well MW antennas and the ground system ARE just like dipole antennas. And you certainly do not have 20 feet of space separating the main radiator element from its counterpoise element!
RFB
Back in 2007 kc8gpd said, "A local and unnamed station wanted him off the air for some reason."
Why can we not know the name of the complaining station?
Now, 2012, kc8gpd adds, "There is much more to this story than just a licensed station reporting this guy."
Does that mean a licensed station didn't report him? Anyway, it makes a good first sentence toward explaining what happened.
Where is the rest of the story?