Rich

Below is a chart showing the effects of using an antenna system with radiating conductors exceeding the 3-meter FCC limit allowed by U.S. 47CFR §15.219.

RE: Using a 130-ft horizontal wire as an antenna for “Part 15 AM” stations

A horizontal wire produces horizontally polarized radiation, which has very high loss relative to vertical polarization as it propagates along the surface of the Earth.  Also, it does not radiate equally well in all compass directions.

A vertical conductor (vertical…[Read more]

RE:  … if we or another party filled for a modification or amendment to 15.219, allowing the ground lead to exceed 3 meters (not the antenna) would you oppose it?

Not if the claims of the party or parties filing for the change(s) in Part 15 Rules are based on accurate, scientific principles with respect to the operation and performance of…[Read more]

RE: .. I live in a one story house. A thought Rich, coming from a Ferrite Filter Choke under the transmitter, going down the 13 feet, 1.48 inch meter pole, would a 6 gage insulated wire be sufficient to ground?

Not legally, because r-f ground potential does not exist along the exposed length of such a wire, regardless of its gauge (whether…[Read more]

RE:

… What about using a *shielded*ground lead from your location say 30 ft up?
A shielded ground lead? … You would be using center conductor as the actual lead and the shield would prevent radiation. The center conductor at ground level would directly connect to your stake or radials underground. …

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Unfortunately, while both c…[Read more]

RE: …The wire between the Ferrite Filter Choke and to whatever we choose to attached to use for a ground, be it a short 3 foot galvanized galvanized pipe driven into the ground, a short copper ground rod, or a cold water pipe, that wire would be dismissed as a part of the radiator, making it in compliance with Rule 15.219 because we are within…[Read more]

RE: I think how the Ferrite Choke Coil works is we take the copper wire at 10 inches from the Part 15 Transmitter, insert this ground wire going to the copper rod, this making the ground wire not be a part of the radiating part of the antenna for the transmitter, but “Only” for electrical grounding only in case the transmitter took a lightning hit…[Read more]

RE:

Wouldn’t ground conductivity come into play here as well as it did for us Licensed Commercial AM Broadcasters?

Yes.

It’s not really signal in my situation the problem, as I explained “sort of” in the beginning, it’s these severe thunderstorms we get here with lightning with such a charge that the transmitter antenna doesn’t have to tak…[Read more]

From an earlier post in this thread: “The problem is our Audio Division at the FCC sees the ground wire as a part of the radiator, thinking this increases field strength.”

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And with good reason, too.  Please refer to the graphic below.

RE:  But maybe Rich can weigh in on this.

As usual in engineering matters, accurate answers to apparently simple questions can require a deep understanding of the Physics involved.

Correctly understanding these topics requires the careful study of appropriate antenna engineering textbooks, such as ANTENNAS For All Applications 3rd Edition…[Read more]

RE: Is there a relationship between a wire cut to wavelength and a length of wire wound on a loop antenna to reach resonance?

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There is a relationship as far as the reactive terms of their feedpoint terminal impedance both approaching “resonance” (jX = 0) at some given lengths of straight or coiled transmit antenna conductors, on a…[Read more]

Below is a graphic page that can be useful in the discussion of this topic.

The concepts posted earlier sound simple, but much complexity exists when they are more fully evaluated.

RE:  I’m actually amazed that I’m getting a mile. It’s pretty noisy here. Since I’m using the buildings electrical system’s ground, I’ve noticed a huge difference in signal as I cross over the property line. Once I leave it, the signal drops off a lot.

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Below FWIW is a graphic with an analysis of the range/coverage of an unlicensed s…[Read more]

RE: Your idea by looking at the drawing is a savior! My wife has seen your drawing, but like me, she has no idea how long each radial has to be. ____________

Probably you are referring to the drawing in the graphic below.

Please note that the lengths of the buried radials are given as the 4th “bullet” in the list near the top of of that…[Read more]

A few comments about the post first above:

RE:  I have had to install a copper ground system for my Commercial AM Station I owned before I retired from that. In plumbing, copper is better than old gavanized pipe!

Just to note that almost all AM broadcast stations use one (or more) galvanized steel towers as radiators.  When used with good, b…[Read more]

Mark wrote: Seems logical that if you want to protect something don’t have it connected to earth to make it easy for lightning to hit it, in this case the transmitter.

Connecting the chassis/r-f ground bus of the transmitter via a low-impedance path to the electrical potential of the Earth helps to protect the transmit system, because it “…[Read more]

ArtisanRadio wrote: The safest and most legal way to run a transmitter…is to install it at Earth level, using a short ground lead to one or more buried ground rods. …If you locate the transmitter well away from any obstructions, such as buildings, you’ll get as much range as an elevated install.

The first sentence in the clip above is a…[Read more]

The title of FCC §15.231 seems appealing, but reading further into its following text brings disappointment (see below):

Below is a calculation of the performance of a “typical” Part 15 AM transmit system, from a spreadsheet using the appropriate equations appearing in antenna engineering textbooks.

The impedance of the antenna system “seen” by the transmitter there is the sum of the radiation resistance with the r-f resistances of the loading coil and the path to…[Read more]

Clearly Neil has taken the time to design, install, and optimize his transmit antenna system in order to achieve that 15-16 kHz audio frequency response at the output of his receiver.

Even if/when the transmitter itself has that modulating bandwidth, probably the r-f bandwidth of most Part 15 AM antenna systems, perfectly optimized, is narrower…[Read more]