Is it in compliance?

[Tom Wells]

A thread on a different board related to part 15.219 530-1710 antennas made me begin to wonder about whether
ANY elevated AM antenna/transmitter combo sold for "legal" part 15 operation can be legal if an earth ground is connected.

I visited this site,

http://www.am1000rangemaster.com/index.html

Certainly currents in the ground line result in radiation, and fall under the "total length" of radiator permitted?
I see nothing in the photos of the transmitter or diagrams to suggest they've eliminated RF in the earth line.
The Rangemaster site shows pictures and diagrams, all suggesting elevating the antenna and grounding it.
One particular claim of 4 miles for a woodsy location, would probably be the one in a picture that shows something like a fire-watch tower.

Are these manufacturers trying to sneak one by people who don't know any better, any will then be liable for fines?

Does this sound like it is in compliance?

 

[Turntable]

It's pretty hard to get a part 15 setup to do much, no matter how much height or how much gain the antenna has. If it truly is part 15, and meeting the lower-than-low power requirements, it would be pretty hard to create any interference or arouse any FCC attention. I know, I've tried

Actually I should probably clarify that... I didn't try to create interference or arouse FCC attention. I tried to get coverage-- and pretty much failed.

-A

 

[rfry]

Certainly currents in the ground line result in radiation, and fall under the "total length" of radiator permitted? ... Are these manufacturers trying to sneak one by people who don't know any better, any will then be liable for fines? Does this sound like it is in compliance?

The concept used to justify this by some Part 15-ers and OEMs is that an "r-f ground" exists at the top of a large OD conductor whose other end connects to conductors buried in the earth. Therefore they only include the length of a short, smaller OD wire that leads from the tx ground terminal to the top of the large OD conductor in the 3-meter total length of the radiator plus ground lead that is defined in 15.219. They consider the short wire as the ground lead, and the connecting point at the top of the long wire as ground.

Another approach is to define the large OD wire to function only as safety ground, for lightning protection.

As you point out, unless r-f current is prevented from flowing in the total length of the exposed conducting path from the tx ground terminal to the earth, such current will produce radiation. It is possible (and likely) that the radiation from that conducting path will be many times greater than from the ~3-meter radiator that they consider as the complete antenna.

But with no ground plane reference, the ~3-meter radiator connected to the Part 15 AM tx r-f output connector would have no return path for current to exist in the 3-meter section. System radiation efficiency would be close to zero.

Paper 3 at http://rfry.org/Software & Misc Papers.htm uses NEC analysis to develop this in more detail.
//

 

[Tom Wells]

How can a change of conductor size qualify as anything other than a tiny LRC discontinuity?
The discontinuity iself is a loss in the L and clearly the heart of their claim.

If they're going to claim it's a "bad" connection, poor performance Must result.
If they're truly trying to get the best result, it is in their interest to get as much RF current here as possible.

Looks like a classic case of weasel words and creative definition.

So I'll propose this....

What if your Xmitter is in the basement, your ground rod through the floor, connected short as possible.
We'll say it's 3 meters. Now the 100 mw output is turned on (both these we'll define as clearly compliant).

Now we'll define it as close-coupled, with a standard, compact presentation.

But if we open the tuning tank circuit and find a way to distribute L and C creatively over a large area,
can't this result in good radiation?
Yes, I know about the dangers and precautions.
Since this would be a TUNED CIRCUIT of the part 15 compliant transmitter, part of the ouput tank tuning for load,
it is clearly "not the antenna" but part of the transmitter proper.
I see no physical dimension limitations on the size, shape, placement of any parts of the circuit, or even a referernce to
the size of a transmitter. Or whether some components might not be remote from the rest of the circuit.

I've read about HF vertical-oriented loops, just never tried one.
I'd like to try a horizontally laid capacity plate in my attic as the C, with variable L at basement floor level.

Does anyone 'member when New Jersey was taxing AM towers in the Meadowlands, but some smart engineer stopped it?
He told Jersey that they were not station "property or structures". They were, in fact part of the radio circuit, and thereby not subject to their silly ol' tax, as written.

And what's this about states legislating radios law when authority is not given to states, but reserved
for the FCC nation-wide?