JUST TO WIP UP THE TROOPS

[ellenparks]

Ok, concerning part 15, suppose for arguments sake I build a part fifteen station with a transmitter capable of creating no more than 100 milliwatts output. I then connect a verticle antenna no longer than 3 meters to it. This transmitter is powered by an internal battery. Also associated with this transmitter is a receiver capable of picking up some sort of audio signal from a source other than on the frequency my transmitter operates on ( an STL). the receiver is also battery powered from within . I then attach a group of 8 horozontal radials maybe 20 feet in length each give or take to the chassis of the transmitter so as to create a ground plane. I then elevate the entire apparatus on a PVC plastic pipe maybe 75 feet in the air ( ya I know PVC won't go that high but indulge me here ). There would be no electrical ground and no lead to ground from the elevated apparatus the entire thing would be isolated from earth ground but at the same time rf currents could circulate due to the horozonatl radials.

My question is: Using the above which appears to adhear to FCC rule 15.219, would my signal extend farther than the limits set by 15.209. If so how much? Would the commission find my installation to be illegal due to precident as opposed to letter of the law?

Mr. Fry would you like to weight in on this one?

 

[rfry]

Mr. Fry would you like to weight [sic] in on this one?

IMO, such conjecture may or may not be viewed by the FCC as compliant with 15.219, for the parameters you posted.

 

[ellenparks]

That's certainly a safe answer LOL but will it create a stronger signal than placing the whole thing as discribed at ground level?

 

[ellenparks]

Let me rephrase that: will it create a larger coverage area than at ground level?

 

[RPowers]

Using the above which appears to adhear to FCC rule 15.219..

Does it?

 

[rfry]

...My question is: Using the above which appears to adhear to FCC rule 15.219, would my signal extend farther than the limits set by 15.209. If so how much?

Earlier this year I modeled a system isolated from the earth, that used base radials (link below). This model produces about 56% more groundwave field intensity at a distance of 0.31 miles than if the same system was installed with its base at earth level, used no radials, and its r-f ground terminal was connected to a buried ground rod having 35 ohms of r-f resistance.

Elevating the version with base radials to 75 feet above the earth (about 0.13 wavelengths at 1700 kHz) would not affect groundwave coverage significantly. There may be a tendency to expect that, considering that height above the earth does affect the space wave coverage of FM/TV stations.

All of the systems described above would outperform a system compliant with 15.209, whose 1700 kHz groundwave field at 0.31 miles would be on the order of 0.8 µV/m.

Would the commission find my installation to be illegal due to precident [sic] as opposed to letter of the law?

That is an FCC matter. Suggest you send your proposed system concept to them, and ask for their comments.

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

 

[ellenparks]

I notice that your model is located 9 inches above the ground. Is is possible to chart the field strength level at a fixed difference as the model is raised above earth? Is there anything of significance to be noted as the model passes through various wavelength distances as it is elevated?

 

[rfry]

Is there anything of significance to be noted as the model passes through various wavelength distances as it is elevated?

There would be for a space wave, when the transmit system elevation above earth was a significant fraction of a wavelength.

But the useful radiation from "Part 15" monopole radiators in the MW band is via the ground wave, not the space wave, and the groundwave from a MW monopole using base radial wires as in my model essentially would be the same as shown in the model even if that system was elevated to 75 feet.