Part 15 it can't be legal because:

[CaptBob92]

I'm curious, as I understand it a fair amount of people are running part 15 stations. They believe the definition in the FCC rules that ( paraphrasing here too lazy to look it up ) the antenna length " and Ground lead " together can not exceed 3 meters means to the ground point.

The problem here is in the definition of the " Ground lead " which these guys take to mean the distance to " a grounding point "
If the transmitter happened to be sitting atop a hundred foot tower ( which is grounded ) they believe the actual length of their ground lead would be the distance from their transmitter to the top of the tower. But as every engineer knows, the tower itself becomes the grounding lead because it is between the transmitter and actual ground. Or then tower and the antenna on top of the transmitter ( probably about about 8 feet long ) end up being an antenna being fed ruffly in the middle .

There is no way this can be deemed legal. the only legal way is to place the transmitter within a few feet of actual ground ( maybe a ground rod ) which results in a usable signal traveling only a hundred feet if that. I've tried it.

So, how is it so many people are getting away with coverage over a couple of miles? Or are these stations illegal. Can anybody show me a legal way to get that kind of range with part 15?

 

[KR4BD]

I'd like a good explanation, too. We have a billboard, supposedly running 100 mw here in Lexington, Ky transmitting the UK fight song 24/7 on 1630 which can be heard for several miles. I've tried using 100 mw transmitters and about 100 feet seems to be "the limit".... What am I missing?

 

[rfry]

Part 15 AM is legal when transmit systems functionally observe all of the limits given in 47 CFR Part 15.219. However when they do, the useful coverage area they provide is not as great as when they exceed those limits. This leads some to promote and use systems that functionally are not compliant with Part 15.219, while claiming that they are.

CaptBob92's comment about the effect of using long, radiating ground conductors with some "Part 15 AM" setups is absolutely correct. And the FCC has been issuing NOUOs to the operators of some those systems.

One manufacturer of Part 15 AM transmitters has introduced an optional r-f choke to be inserted where the ground lead connects to the transmitter ground terminal, to limit the effective length of the radiator to 3 meters or less.

But if that choke provided just a 20 dB reduction of radiation from the ground conductor, then the transmitter with its 3-m whip may as well be installed with its chassis a few inches above the earth and used without the r-f choke, because its performance likely would be better than when using an effective r-f choke in the ground lead of an elevated system.

This is shown in the analysis at the link below, which compares the coverage radius for four system setups, with other parameters held constant.

http://i62.photobucket.com/albums/h85/rfry-100/150_microvolt_per_meterRadius_Part_.gif

RF

 

[CaptBob92]

That's what I thought. Back in 2000 I ask an FCC inspecter out of the Detroit office what he would do if he found one of these operating and he said he would write a NOUO. His example was one located atop a multistory office building in Cleveland where the whole building was radiating. But then I read these stories of inspectors saying it's alright to ground to the top of such a thing. I wondered if the FCC interpritation of the law had changed. I would think not.

 

[WCWalker]

I'm curious, as I understand it a fair amount of people are running part 15 stations. They believe the definition in the FCC rules that ( paraphrasing here too lazy to look it up ) the antenna length " and Ground lead " together can not exceed 3 meters means to the ground point.

The problem here is in the definition of the " Ground lead " which these guys take to mean the distance to " a grounding point "
If the transmitter happened to be sitting atop a hundred foot tower ( which is grounded ) they believe the actual length of their ground lead would be the distance from their transmitter to the top of the tower. But as every engineer knows, the tower itself becomes the grounding lead because it is between the transmitter and actual ground. Or then tower and the antenna on top of the transmitter ( probably about about 8 feet long ) end up being an antenna being fed ruffly in the middle .

There is no way this can be deemed legal. the only legal way is to place the transmitter within a few feet of actual ground ( maybe a ground rod ) which results in a usable signal traveling only a hundred feet if that. I've tried it.

So, how is it so many people are getting away with coverage over a couple of miles? Or are these stations illegal. Can anybody show me a legal way to get that kind of range with part 15?

Utilizing this logic one could surmise by definition that the Mississippi River is actually part of the Gulf of Mexico. While both may be considered bodies of water, they are by definition and design, two distinct components that operate independently of one another, despite the fact they are connected.

If you understand how the regulations are written you'll note there is nothing in the Part 15 rules that limit the height or placement of a transmitter. And by definition, a mounting pole whether it be made of wood or metal, by definition is not necessarily a part of the antenna. Bear in the mind the transmitter itself also radiates signal too but it is not by definition a part of the antenna or ground.

The FCC has neither the manpower or the money to shut down all of the stations that you and others like you would like to see shut down. They are busy going after the high powered FM pirates and licensed stations that operate as pirates. It's no different than a cop sitting taking radar at the side of the road. A bunch of cars go by doing perhaps 1 to 8 mph over the speed limit and he won't bat an eye. But a car doing 12 mph over the speed limit goes flying by and he'll go after it.

I think the FCC recognizes that they would rather have a bunch of people using the AM band to operate Part 15 AM stations than have to deal with hundreds and perhaps thousands more true pirates on FM. Part 15 AM is a safety valve that prevents an even bigger problem from occurring on the FM band.

 

[WCWalker]

I should also add that any licensed broadcaster with some common sense will realize that not one single Part 15 AM radio station, regardless of its range is going to be a serious challenge for its listeners or revenue streams.

The following is your biggest threat and I suggest you find a way to put a stop to this otherwise you'll see thousands of licensed stations leave the air.

http://www.noperformancetax.org/

 

[rfry]

... Utilizing this logic one could surmise by definition that the Mississippi River is actually part of the Gulf of Mexico. While both may be considered bodies of water, they are by definition and design, two distinct components that operate independently of one another, despite the fact they are connected.

Note that the above analogy does not apply to a short "ground lead" (the Mississippi of the analogy) connected to another, long conductor leading to a functional r-f ground --typically, something buried in the earth.

A short ground lead connected to a long ground conductor do not operate independently of each other. They function together as a single conductor, and together they contribute most of the radiation from an elevated Part 15 AM setup.

Physics shows that an r-f ground cannot/does not exist at the top of an exposed conductor of any configuration even when the bottom of that conductor is attached to buried grounding rods, radials, water pipes, etc. That long conductor can take any form: a "massive ground wire," a metal flagpole, a tower, a TV mast, a water tower, the steel frame of a billboard or high-rise building, etc.

That is the reason why such conductors of all configurations radiate when used with elevated "Part 15" AM systems, and mean that such systems functionally do not meet Part 15.219(b).

RF

 

[WCWalker]

This is a case of one or more people that are attempting to redefine not only the name but categorization of the working components of not only a Part 15 station but also, licensed stations.

This is like saying the hair on the top of your head is actually part of your chest or arms. Yes, it may physically connect by the follicles that are inside your head but that does not mean by definition it is also part or another part of the body. Utilizing your logic one could surmise the entire antenna and transmitter is also a ground because they are all interconnected. Or, in the case of a 1kw AM for example, the entire tower should be considered a ground because it is connected to the ground system of the tower.

This same rationale applies in this case. There may or may not be a conductive environment that exists beyond the short ground lead being tied off on another object, but by definition that object that it is tied off to is not a ground.

 

[CaptBob92]

William,
The question I raised here was whether or not the part 15 stations are operating legally not the philosphy of if or why they should.

Actually, I would rather see the commission clearify the laws and make it possible to operate part fifteen for a reasonable distance of a mile or two with the criteria being a maximum field strength at a prescribed distance instead of how the transmitter is installed. ( minus interferrence to licensed stations of course ) As long as you would meet that criteria you were legal and they would leave you alone.

No, they are no threat to licensed stations and yes the upcoming law may put all music stations under and we should work against it but that's not what I ask.

It is clear to me that the argument that the thing the transmitter sits upon is not a ground lead is not valid no matter how you slice it.
Therefore if you place your part 15 transmitter high in the air and ground it to the object it sits upon ( assuming it's not a nonconducting thing like a plastic mast ) the thing it sits upon becomes the ground lead.

Can anybody think of a way around this that would get better radiation without the ground?

 

[rfry]

Utilizing your logic one could surmise the entire antenna and transmitter is also a ground because they are all interconnected. Or, in the case of a 1kw AM for example, the entire tower should be considered a ground because it is connected to the ground system of the tower.

It is the opposite. My post above, and physics both state that the "entire antenna and transmitter" and an AM tower are NOT ground.

That is the reason why they radiate.

RF

 

[WCWalker]

William,
The question I raised here was whether or not the part 15 stations are operating legally not the philosphy of if or why they should.

Actually, I would rather see the commission clearify the laws and make it possible to operate part fifteen for a reasonable distance of a mile or two with the criteria being a maximum field strength at a prescribed distance instead of how the transmitter is installed. ( minus interferrence to licensed stations of course ) As long as you would meet that criteria you were legal and they would leave you alone.

No, they are no threat to licensed stations and yes the upcoming law may put all music stations under and we should work against it but that's not what I ask.

It is clear to me that the argument that the thing the transmitter sits upon is not a ground lead is not valid no matter how you slice it.
Therefore if you place your part 15 transmitter high in the air and ground it to the object it sits upon ( assuming it's not a nonconducting thing like a plastic mast ) the thing it sits upon becomes the ground lead.

Can anybody think of a way around this that would get better radiation without the ground?

Considering that there are thousands of these transmitters already in use and more going out every week, it is not likely the interpretation of the rules by the people that set the rules is going to change any time soon.

This matter is less of a technical one and more of a legal one. By definition the transmitter is not a ground.

 

[WCWalker]

Utilizing your logic one could surmise the entire antenna and transmitter is also a ground because they are all interconnected. Or, in the case of a 1kw AM for example, the entire tower should be considered a ground because it is connected to the ground system of the tower.

It is the opposite. My post above, and physics both state that the "entire antenna and transmitter" and an AM tower are NOT ground.

That is the reason why they radiate.

RF

But some people also claim the entire structure right on down to the ground is a antenna. Again, we've got people that are trying to redefine components that work together but also separately from one another.

I've talked to numerous engineers that don't agree with your assessment of the situation.

 

[Goat Rodeo Cowboy]

Utilizing this logic one could surmise by definition that the Mississippi River is actually part of the Gulf of Mexico. While both may be considered bodies of water, they are by definition and design, two distinct components that operate independently of one another, despite the fact they are connected.

Excellent logic. An ocean is an ocean. A river is a river. (OBJECTS)

Further logic. An antenna is an antenna. A building is a building. The earth is the ground. (OBJECTS)

Logic hits brick wall: In transmitting, grounding is a FUNCTION, not an OBJECT.

Confounding logic: A barge can navigate ocean. A barge can navigate river. (FUNCTION)

Confounding logic: Barge traveling ocean = barge traveling river = transportation. (FUNCTION)

Confounding logic: Radio wave traveling ground wire - Radio wave traveling supporting structure = transmission of radio engergy. (FUNCTION)

 

[rfry]

But some people also claim the entire structure right on down to the ground is a antenna.

If one accepts the rather standard definition that an antenna is any structure that radiates r-f energy, then all of the long "ground" conductors I listed earlier are part of the antenna system of an elevated Part 15 AM setup.

Calling that long conductor "ground" does not prevent it from functioning as a major, radiating component of the antenna system.

RF

 

[ChiefEngineer]

This comes down to 2 things : 1) Good Engineering practice; and 2) interpretation.

A famed consultant when talking a client through mounting his omni fm on a water tower (non da) explained he should fully explain and describe (along with drawings) the antenna. This was obviously affecting the rf signal and made the station directional. It was granted a non da license and served parts of it's service area WELL and other areas not at all. His question: Is it good engineering practice? No. But it is accepted because the purpose (haha) wasn't to make the station directional it was simply to mount the antenna. Same logic applies to any FM mounted on a 10 foot plus tv tower.

The Part 15 process is so dubious because of the time and efficiency of the gov. All the wireless internet providers unlicensed because they mount their amps on the tower. All the wireless routers. Same principle. Same process.

Not an easy answer but some common sense must come into play.

 

[WCWalker]

Another issue that comes into play is the UL laws. These Part 15 transmitters have been designed and built to meet UL laws and also FCC regulations.

 

[rfry]

These Part 15 transmitters have been designed and built to meet UL laws and also FCC regulations.

... IF they are installed in such a way as to functionally meet those laws and regulations.

That doesn't happen merely by act of ownership.

 

[WCWalker]

These Part 15 transmitters have been designed and built to meet UL laws and also FCC regulations.

... IF they are installed in such a way as to functionally meet those laws and regulations.

That doesn't happen merely by act of ownership.

Yes, we know. You've been going on about this ad nauseam year after year after year after year after year...

 

[rrsounds]

These Part 15 transmitters have been designed and built to meet UL laws and also FCC regulations.

... IF they are installed in such a way as to functionally meet those laws and regulations.

That doesn't happen merely by act of ownership.

Yes, we know. You've been going on about this ad nauseam year after year after year after year after year...

The reason Mr. Fry must repeat himself is that people keep finding new ways to re-interpret physics to suit their desires.

Any knowledgeable engineer involved in the industry will tell you that he is completely and unarguably right, in the both the legal and electrical theory senses.

He is also very patient with people who have a poor understanding of how radio works, but not so patient with people whose agenda is to circumvent the law with bogus claims.
You go, Richard!


Kind Regards,
David

 

[ChiefEngineer]

There has never been an FCC investigation of any of the Part 15 devices that are out there for wireless internet, or for example Sirius XM that has the ability to wipe out our local FM in it's primary service area.

Several years ago the FCC determined our tower didn't meet FAA regulations because it wasn't properly painted. 800 feet tall. The tower owner refused to paint it. The cost would have bankrupt them. The Bank One Tower was in fact never painted and some common sense prevailed.

A tower or billboard is grounded by regulation and good engineering practice.

Hamilton suggests you add a standoff ground wire which will radiate. I see a problem with this.

If your ground lead is grounded to the tower (which is grounded) you didn't install the tower to be a long ground wire. If your house is on the 12,000 foot hill outside of town (which is also grounded by earth) at a higher height does this mean you should dig a hole or move?

External grounding wires that are added for the purpose of expanding coverage are issues but the use of existing facilities don't seem to be remarkable.

Sirius XM have money so they aren't under the same Rules we are.