Part 15.219(b) rule

[Hamilton]

Subpart of Part 15.219:
(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.
There has been much controversy about this simple rule. But objectively interpreted by someone in the engineering field, the meaning seems clear. We know what a transmission line is, basically the coax cable in a transmitter, antenna system. So legally a transmitter – Coax - Antenna system seems to be out of the picture since a system with a coax cable of any length would violate this rule. Next is the Antenna. In most systems the Antenna is where your 3 meter length is. Now we come to the infamous term “Ground lead.” In research on the term “Ground lead” I have found that the term seems to always refer to a “wire” that connects an electronic device to a local ground. An example would be a wire that grounds an oscilloscope to the frame of a test bench, or whatever else was being used for Ground. This definition has also been the interpretation of the “ground lead” by many in the FCC itself for years.
It is a ridiculous stretch to interpret “Ground lead” as the entire conductivity between the ground terminal of the transmitter circuit board and the dirt in a transmitter system.

For some reason that I don’t understand, some months ago some people seem to decide to define “Ground lead” this way. This interpretation is a far stretch and just doesn’t seem to fit the 15.219(b) wording, and changes Part 15.219(b) into something it is not.
Does the intentional signal get into the local ground and somehow, sometimes get radiated by ground systems? Sure. But the problem is that Part 15 says nothing about additional radiation. In the past if part of the ground system is obviously designed to radiate then usually the agent would ask that it be removed.

My units (RangeMaster) have been inspected many times in the past mounted on the top of poles with a ground lead connected to the pole, (and other ground configurations) and passed FCC scrutiny with no issue.
The job of the FCC agent is to enforce the law, not to interpret it, it shouldn’t be thrust upon the field agent to do any interpretation. Any uncertainty about interpretation is difficult for the public and field agents. Interpretation and enforcement should be consistent and uniform across the board.

Part 15 LPAM has been a great benefit to many. Schools, non-profit organizations, churches, hobbyists, those who can’t get an LPFM all benefit from the service. This “circuit board to dirt” interpretation of “Ground lead” that has been suggested would cause these organizations to have to reengineer their Part 15 installations. In many cases the only choice could be placing the transmitter in a vandalism prone area, or the entity may have to disconnect the ground from the transmitter. In the case of our RangeMaster transmitter disconnecting the ground from the transmitter is a hazard to life and property since doing so disables the lightning protection.
If you approach an engineer that knows nothing about part 15 and show them the rule I have found that 100% of the time the term “Ground lead” is clear, the wire from the transmitter to the tower, mast or other local ground. When I mention that some people are trying to interpret “Ground lead” as “the entire conductivity between the ground terminal of the transmitter circuit board and the dirt” some of these engineers have gone ballistic on me trying to explain to me how ridiculous that is. It is ludicrous that someone in NYC has to feel that to be legal with their Part 15 they are going to have to drill a hole down to the dirt, and mount their transmitter out on the sidewalk. Not to mention many Part 15’s are not even designed to be installed outside. People are going to be tripping over all these Part 15’s!

 

[rfry]

Hamilton wrote "It is a ridiculous stretch to interpret “Ground lead” as the entire conductivity between the ground terminal of the transmitter circuit board and the dirt in a transmitter system.... Does the intentional signal get into the local ground and somehow, sometimes get radiated by ground systems? Sure. But the problem is that Part 15 says nothing about additional radiation. In the past if part of the ground system is obviously designed to radiate then usually the agent would ask that it be removed."

Part 15.219(b) does limit the length of the antenna, feedline and ground lead to 3 meters. And why does it do that? Because the FCC intends to limit the radiation from Part 15 systems. Other things equal, radiating lengths longer than 3 meters produce greater signal strengths. This is a reality of physics that should be easily recognized and accepted by any competent r-f engineer. Antenna engineering textbooks show why.

One type of radiator used by some broadcast stations consists of an UNinsulated, vertical steel tower. The tower legs are bonded to a buried ground system of 120 radial wires each about 1/4-wave long. The tower is fed through a wire from the transmitter connected at some physical height above the earth where the impedance is suitable.

The radiation efficiency of this shunt-fed tower is the equal of a conventional, insulated (series-fed) radiator of the same height and with the same buried radials.

Yet by your definition of what comprises a ground, Keith, this structure would all be at ground potential, and radiate nothing. This example shows the fallacy of such an argument.

Unless r-f current is decoupled from them, all conductors connected to the ground terminal or chassis of a Part 15 AM transmitter become part of its antenna system, whether or not they reach a "dirt ground."

If r-f current flows along an exposed conductor, that conductor radiates. Period. It's that simple.

All of the r-f current flowing through whatever you wish to define as a short "ground lead" attached to a "massive ground wire," flagpole, tower, billboard steel or whatever also will flow along those conductors. Hence they will radiate, and can extend the effective length of the "Part 15" AM antenna system beyond the limits of 15.219(b).

A true r-f ground does not radiate. That's the definition of an r-f ground. Recognition of this reality is the reason for the posts that describe this relevance to Part 15 AM antenna systems, and the many posted beliefs that don't recognize this.

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[Hamilton]

Fry,
All that you say just doesn’t matter, you don’t seem to get it, read the rule. Follow the rule. Like I have said before the FCC doesn’t need your help in this matter, I’m sure they were aware of all these concepts when they wrote the rule and took all that into account.

Fry said “Because the FCC intends” Fry, Are you the FCC director? Do you even work for the FCC? How is it you are the privileged among us to know what the FCC intends? I wonder why some on this board purport creative interpretations of a simple rule that is so damaging to the Part 15 world. What exactly is your motivation here Fry?

 

[rfry]

...I wonder why some on this board purport creative interpretations of a simple rule that is so damaging to the Part 15 world.... How is it you are the privileged among us to know what the FCC intends? ... What exactly is your motivation here Fry?

You are creatively interpreting Part 15.219(b) when you post that it doesn't matter what the short wire you define as THE ground lead connects to.

Physics shows that if it connects to an exposed wire or other conductor (grounded or not), that conductor will radiate, effectively adding to the 3-m legal length of the antenna system.

My motivation is to state the physical reality of these systems so that Part 15 AM users will understand how such systems truly function.
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[Hamilton]

Fry said “My motivation is to state the physical reality of these systems so that Part 15 AM users will understand how such systems truly function.”
Fry, I think the only entity qualified to do this fully is the creator.

Where in Part 15.219 does it specify what the “ground lead” connects to? You must agree that is does not specify.
“could you go back and read my original post carefully” Personally I would assume that the “Ground lead” connects to “Ground”.

 

[rfry]

Personally I would assume that the “Ground lead” connects to “Ground”.

Where we differ here is whether or not a radiating conductor such as "massive ground wire," flagpole, tower, billboard steel or whatever is a true r-f ground.

A true r-f ground will not radiate -- that's the definition of an r-f ground. ALL exposed conductors such as those named above that carry r-f current will radiate. Therefore they can not and do not function as an r-f ground, no matter what we call them, or how much we wish otherwise.
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[WCWalker]

Whether or not it radiates seems to be irrelevant at this stage. What matters is WHAT precisely is the definition of the ground wire. That seems to be the 18" wire that comes out of the transmitter (Rangemaster) and then gets tied off on an object. The FCC seems satisfied to see it tied off to "something" as long as the wire is not one continuous lead to the ground. Even then, I've heard in more than one instance where the FCC ignores a ground lead that extends beyond the 18" maximum with the Rangemaster transmitter.

R. Fry, you obviously have a different definition of the ground wire than the FCC. At one time perhaps, the definition you are using might have been relevant. But times change and so does technology and its a sincere shame to see someone with some obvious book smarts acting so oblivious to the facts and FCC's interpretation of its' OWN rules.

Here's a corny but good analogy: A paved road suddenly becomes a dirt and gravel road. By definition the dirt portion may still be called a road but it cannot be called a paved or improved road. Yes, you can still drive on it or walk on it but it is no longer a paved road even though you can move along it in the same manner but perhaps a bit more slowly.

 

[rfry]

Whether or not it radiates seems to be irrelevant at this stage. What matters is WHAT precisely is the definition of the ground wire. That seems to be the 18" wire that comes out of the transmitter (Rangemaster) and then gets tied off on an object. The FCC seems satisfied to see it tied off to "something" as long as the wire is not one continuous lead to the ground. (etc)

That's a lot of "seems," which is not the most reliable approach toward this subject. People can have honest differences about what seems right to them.

My goal in posting is to base my comments on sound, unequivocal engineering principles that can be verified by anybody wishing to do. I'd rather write about things that are true, rather than just seem true.
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[WCWalker]

That is your opinion. By FCC definition, based upon my personal experiences and that of others,the ground comes to an end when the ground lead from the transmitter is tied off to another object. That may seem like an opinion to you but it is clearly a fact that I and countless others have used this method to pass FCC inspections of our part 15 AM radio stations.

You have too much spare time on your hands. Why not find something constructive to engage in?

 

[Hamilton]

Thanks William,
It is a simple thing, read the rule.

 

[rfry]

It is a simple thing, read the rule.

But also understand that any conductor connected to that short ground lead carries the same r-f current that the ground lead does, which means it will radiate.

Part 15 AM users and even some FCC inspectors may not realize this, but physics shows that the radiating, conducting path does not end where the ground lead is "tied off" to another elevated conductor.

The FCC may pass such systems, and as per some recent citations -- they may not.

It's up to the user to choose how s/he wants to operate.
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[WCWalker]

Uh, yes I do understand this. Hence, the analogy for the paved and dirt road. The signal/car may still be able to travel along the same path, albeit at a diminished speed/power level, but once it leaves the paved road/copper wire and enters into another object, it is then defined as something dififferent.

 

[WCWalker]

Here's a better analogy and one that should make my point crystal clear.

Long Island Sound is not part of the Atlantic Ocean even though it is filled with salt water. Granted it is connected to the Atlantic Ocean and by all outward appearances does seem to be the Atlantic Ocean but it is not. The Connecticut River empties into Long Island Sound. Brackish water at the mouth of the river soon is replaced by freshwater just a few miles up river. Even though each of these bodies of water are fully connected and integrated to some degree, that does not mean each body of water, because of their design, is defined as one and the same.

This same logic applies to the ground lead from the transmitter. Yes, even if it is tied off after a foot and a half it may still radiate some r-f but by definition, just like the CT River or Long Island Sound, it is no longer considered the ground lead. Get it?

 

[rfry]

Yes, even if it is tied off after a foot and a half it may still radiate some r-f but ... it is no longer considered the ground lead. Get it?

Let me ask, please -- considered so by whom, and by what rational process?

Call it whatever you wish, but it remains a fact of physics that the conductor(s) connected to the ground lead or chassis of a Part 15 AM transmitter easily can radiate more than the 3-meter radiator and "ground lead" combined.

If the FCC doesn't care how much "coverage" an unlicensed Part 15 AM setup provides, why would they have rules limiting the power input of the transmitter, and the length of the radiating structure?
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[WCWalker]

Surely you gest.

The Connecticut River is your ground lead.
The Brackish water at the mouth of the river leading into Lond Island Sound is your Surge Arrestor or tie off point.
The Long Island Sound is your mast.
The Atlantic Ocean is your ground plane.

Yes, the water or in this case the rf continues to flow top to bottom through the system. But by FCC DEFINITION, not mine and not yours, they consider the ground to end where it is tied off. How many times do we have to tell you this?

You seem to be trying to apply broadcast principles from licensed full power AM stations to Part 15 AM. And yes, you've sounded like a broken record when stating that the same principles apply regardless of the size of the station. But the design of the antenna and tower and ground system of a Part 15 AM transmitter like the Hamilton is not at all like a full quarter wave antenna with a ground system at the base. Enough.

I should also add that UL requires grounding for such devices otherwise they are in violation of a Federal regulation. If lightning strikes the unit it must be properly grounded for the energy to dissipate into the ground.

 

[rfry]

Yes, the water or in this case the rf continues to flow top to bottom through the system. But by FCC DEFINITION, not mine and not yours, they consider the ground to end where it is tied off. How many times do we have to tell you this

If that is the FCC's position, then why the recent citations for elevated Part 15 AM setups with long, radiating ground leads?

I should also add that UL requires grounding for such devices otherwise they are in violation of a Federal regulation. If lightning strikes the unit it must be properly grounded for the energy to dissipate into the ground.

There are ways of providing an electrical ground to a Part 15 AM setup without allowing the ground and other conductors to radiate (except for the 3-m whip). I believe Keith Hamilton makes them available to those who ask.
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[WCWalker]

If you look at one my earlier posts you'll note that I mentioned a surge arrestor in the chain. And some station's find other ways to tie it off.

And, I also mentioned that tying off the ground lead after a foot and a half satisfies the FCC requirement for ground length. Conversely, I make no mention that a ground lead exceeding a foot and a half is acceptable in the eyes of the FCC.

YOU are attempting to redefine the definion of a ground lead. A TV mast or Surge Arrestor is not a ground lead, even if the ground lead is tied off to that object. You sound like Bill Clinton trying to redefine the word "is.

 

[rfry]

A TV mast or Surge Arrestor is not a ground lead, even if the ground lead is tied off to that object.

The r-f current that causes radiation from a "short ground lead" does not end where it electrically connects to a "massive ground wire," TV mast, flagpole etc. With no means to stop it, it continues to flow along the massive ground wire, mast or pole until it reaches whatever constitutes the _functional_ r-f ground, such as buried radials or ground rods. By definition, a functional r-f ground does not radiate.

There is a common belief that the "tie off" connection of a short ground lead to the top of a "massive wire" etc is to being made to a functional r-f ground. But of course if it was a functional r-f ground (and not just called that), then that massive ground wire/mast/pole would not radiate. Yet it does, and effectively extends the radiating length of the antenna system beyond the 3 meter limit.

These are points of physics that continue to go unrecognized, or at least unacknowledged in much of the Part 15 AM world, possibly even including some FCC inspectors.
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[Hamilton]

Fry,
You keep repeating the same sort of thing, the cry is "it radiates! it radiates!" and the we say "we don't care! we don't care!" I think you just like to hear yourself type.
Again, the rule just simply says nothing about radiation, Where does it mention ground radiation?

I'm sure that the engineers that wrote the rule full well know what they were doing, what the ground would do when the ground lead was attached, took all that into account, and simply wrote a simple easy to follow rule that MOST folks could live with.

What is the problem?

 

[rfry]

Again, the rule just simply says nothing about radiation.

No, but it does say that the transmission line, antenna and ground lead (if used) cannot exceed 3 meters.

Some have decided that only a fraction of the length of the conductor(s) connecting the Part 15 AM transmitter to a functional r-f ground needs to be included in that 3 meters.

Physics shows otherwise. That entire conducting path is the "ground lead," and if excessive, can be cause for an FCC citation -- as per some recent examples.
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