Part 15 FCC Range

Hi,

I am glad that Keith Hamilton and I agree that the FCC doesn't object to good range. I told you this in my answer to one of your previous posts.

I am interested in any comments Keith might have made to you about the elevated ground issue.

Neil

Of course. But installing a Part 15 AM tx+3-m whip on an elevated mount with a long conducting path to the ground plane at physical earth IS a violation of 15.219(b), because that conducting path to ground radiates, and the length of the antenna structure then exceeds the 3 meters allowed by 15.219(b). This is a fact of physics that cannot be ignored.

Keith says about the elevated radials and he quotes:" Most I speak with (FCC) are fairly laid back and easy to get along with as far as the grey areas of the law (elevated ground radials) unless they sense that you are pulling sonething on them."

Quote=kint98
Keith says about the elevated radials and he quotes:" Most I speak with (FCC) are fairly laid back and easy to get along with as far as the grey areas of the law (elevated ground radials) unless they sense that you are pulling sonething on them."
________

"Elevated ground radials" are electrically different from the long, conducting path to the ground plane at physical earth that is used by many elevated Part 15 AM tx+3-m antennas, and as is shown in the drawing on the Rangemaster website. Antenna physics shows that symmetrical, elevated radials of equal lengths arrayed in the horizontal plane at the base of a 3-m elevated vertical, and used as reference ground don't radiate significantly in ANY plane.

OTOH, that long, vertical conductor from the elevated Part 15 tx chassis to the ground plane at physical earth will generate considerable radiation in the vertical plane -- often more than the 3-m section, itself.

Are you saying (or reporting) that the FCC doesn't care if the radiating structure exceeds 15.219(b) as long as you aren't "pulling something on them?"

Isn't a radiating structure that exceeds 3 meters in fact "pulling something?"

This is a Catch 22. Not everyone can mount there Tx on the ground, but the Tx needs to be grounded for lightning protection. Also you the transmitter up high reguardless of ground, but again it needs to be grounded for lighning protection. it's ridiculus. One branch of the FCC says one thing, the other says something else, The agents either approve or dissaprove. it's all a crapshoot. it's actually nonsense. they should just right that part out of the rules and just go with a attached 3 meter radiator and allow what ever ground you want. but this is just my opinion. I'm done anyway certified transmitter or not. the FCC got me running over the f/s limits for FM, so if they come back they are not likely to allow even my certified transmitter to pass. just to be hardnoses they'll find a way to make it illegal. the government needs to find something better to do, like actually catching terrorists.

Quote=kint98
Keith says about the elevated radials and he quotes:" Most I speak with (FCC) are fairly laid back and easy to get along with as far as the grey areas of the law (elevated ground radials) unless they sense that you are pulling sonething on them."
________

the desk jockeys in washington are laid back, some of these feild agents act like a police officer, actually a police officer shows more respect to the public than some of these agents.

It is very simple. Read the FCC rules on part 15.

For FM the maximum field strength is specified in the rules.

For AM, the alternative to the field strength rules is specified.

These rules are written in clearly understandable engineering terms based on the laws of physics. I am an engineer and I have no problem understanding the rules. The rules are not based on what you think should be so. You don't want me on the jury when you interpret the rules based on what you think they say and get busted.

I, and others on this board, especially Rich, have interpreted the rules based on engineering knowledge and physics with the intent of keeping you out of trouble. I receive replies to my posts about he said this, they said that, the FCC is laid back about enforcement and that somehow changes the law? You are free to do what you want but I believe that I and others have tried to educate you about the truth of the law and the engineering priniciples which apply. I am not the definitive authority on this, but I do know a few things about radio technology.

I do not accept that the FCC field engineers are being "hard noses" when they enforce the rules.

Neil

Of course. But installing a Part 15 AM tx+3-m whip on an elevated mount with a long conducting path to the ground plane at physical earth IS a violation of 15.219(b), because that conducting path to ground radiates, and the length of the antenna structure then exceeds the 3 meters allowed by 15.219(b). This is a fact of physics that cannot be ignored.

Remember that the FCC does give some latitude on the grounding taking note that grounding is also for protecting your antenna from lightning damage. Thus would not violate part 15.

I couldn't have said it better myself. Most of the FCC staff is pretty laid back and easy going and will not crucify anyone if you stay within the rules. Now if you obviously modify the parameters such as exceeding power limits and the height of your antenna, and you knowingly are breaking the law, then the FCC with play another tune that you would not like. For the most part the FCC is forgiving when you show good faith and intentions on your part 15 broadcasting and stay out of trouble such as the objectional program content, not interferring with other license broadcasters, and so on. Just use simple common sense on your part 15 and you will have trouble free problems with the FEDS.

I guess what Keith is try to say about "pulling on something" is that if you use the guy wires to hold up your tower and if the guy wires DO NOT have insulators on them, then the guy wires act as elevated radials and THIS is the grey area whether the FCC may or may not accept (depends on the mood of the inspector) and might ask you to either A.) remove the guy wires or B.) use insulators for tower support. This is a judgment call on the agent if or when you are inspected. Now using buried radials is ok.

Of course. But installing a Part 15 AM tx+3-m whip on an elevated mount with a long conducting path to the ground plane at physical earth IS a violation of 15.219(b), because that conducting path to ground radiates, and the length of the antenna structure then exceeds the 3 meters allowed by 15.219(b). This is a fact of physics that cannot be ignored.

Quote kint98: Remember that the FCC does give some latitude on the grounding taking note that grounding is also for protecting your antenna from lightning damage. Thus would not violate part 15.

You are stating that exceeding the 3-m radiating length of 15.219(b) is acceptable to the FCC if you say it's just for lightning protection? Can you cite any authority (FCC Rule, policy) for this statement?

There are methods of providing lightning protection for the antenna & tx system that do not require a permanent connection of the tx chassis to the earth, and will not add to the radiating length of the 3-m vertical.
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Hi kint98 and all,

Just a couple of comments about grounding antennas for lightning protection.

Local electrical codes require grounding of masts and grounded protection of lead wires (such as spark gaps or gas discharge tubes) at the point of entry of a building because this provides a path to ground in the event of a direct or nearby strike. The idea here is to protect the building and its contents, and NOT the mast or antenna. I wanted to make that distinction about the purpose of protective grounding.

A second advantage of grounding is that due to wind and other natural effects, a static charge can develop on an antenna which can cause noise in radio reception and damage to transmitters. A DC connection to earth ground such as through an inductor will drain the charge from the antenna.

Stay safe,

Neil

Several decades of taking care of AM broadcast station antenna systems has given me a healthy respect for "unwanted" electrical potential and discharge. I have spent hundreds of sleepless evenings putting antenna networks and transmitters back together after lightning and static discharge do their work. I have even repaired the destruction these forces can impose on FM stations as well.

" Local electrical codes require grounding of masts and grounded protection of lead wires (such as spark gaps or gas discharge tubes) at the point of entry of a building because this provides a path to ground in the event of a direct or nearby strike. The idea here is to protect the building and its contents, and NOT the mast or antenna. I wanted to make that distinction about the purpose of protective grounding." -Neil

I wish local electrical codes took into consideration what happens when you have RF potential at the end of a needle pointing into the sky. Simply put, they don't. I have wrestled for decades with code policy makers to understand the basic theory of adding high frequency RF energy into the equation. Discharge tubes, static chokes and other such devices, when used in an RF environment, become, at best, fuses that burn and arc themselves. Been there, repaired it, own the shirts. I have many stories (I won't bore you with them) about protection devices failing and spending hours finding why the transmitter won't go back on the air. Instead, you get the annoying "chunk-a-chunk-a" sound of the transmitter trying to reset. Broadcast techs know exactly "the" sound I mean.

Lightning, interestingly enough, does not propagate from clouds in the sky. Instead, a lightning strike intiates from an object on the ground. Knowing this should change how you deal with lightning. Many radio practitioners have no idea about how a lightning strike develops. However, they really should take the time, instead of just cleaning up the mess. Its all about saving time and money, isn't it?

The most reliable lightning/safety ground known to man is a 2-4 inch copperstrap from the antenna support to well-designed dissapative ground. Strap is used due to the low inductive reactance to ground. Lightning and static dischrages are very high frequency oscillating arcs. The grounding rules for Part 15 are short sided and incomplete not allowing for safe operation of an elevated "radio needle" charged with RF ready and willing to intiate a real disaster.

So, for someone who has had to deal, on many occasions, with the destructive power of mother nature, I suggest safety, in any venue, should be foremeost. And in CFR 47, this is referred to as "good engineering practice".

Marshall Johnson, Sr.
Rhema Radio - The Word In Worship
http://www.rhemaradio.org

Hello Marshall,

Thanks for your comments.

All my part15 stuff is indoors because I just didn't want to deal with the outdoor protection for the antenna and audio/power lines.

My ham antennas are outdoors and are grounded by means of the coax shields where the lines enter the house right to the electrical service ground stake two feet from the point of entry. Granted, one is a horizontal dipole 25 feet off the ground and the other is a vertical 25 feet up and they are and not space needles, but for 19 years and one direct hit to a nearby tree, I have had no damage to the radio equipment. The strike did take out several telephones, stereo equipment, and a computer modem, but both my transceivers survived.

My point is that simple effective grounding is necessary and probably saved me much grief.

Your statement about lightning originating from the ground agrees with my readings on the subject.

Neil