> We can go on and on regarding this... if you look at the
> calculator and input the results you will see that the
> results give you a 'tower' height and NOT antenna length.
In commercial broadcasting the radiating part of an AM transmit antenna is not a device attached to the top of a tower. For MW broadcast, the entire height/length of the tower IS the active radiator. You are thinking of other kinds of antenna systems, such as FM/TV broadcasting, 2-way radio, etc where that situation exists. But not in AM broadcast. And the FCC program you are using is written so that whatever height you input defines the radiating height/length of the antenna for your model. It couldn't operate any other way. If you don't believe me about this, ask any broadcast consultant of your choice, or research it in antenna engineering textbooks.
> The calculator does not delegate if the antenna is a 3 meter
> or not... only the height of the radiating element... read
> again!
Your understanding of this is incorrect (see my comment above).
> ... the calculator does not distinguish
> between a commercial or part15 antenna... only the variables
> given to it... 100mw, 35 feet height, and 90 radials, 90
> feet long!
But the value "35" used as the height defines the electrical height/length of the total radiator, not just the height of a 3-meter isolated radiator above ground level. Therefore the answer you get will be based on using an antenna over 3X longer than Part 15 AM Rules define.
> > In fact what you are modeling when you input 35 feet into
> > that program is a Part 15 AM tx with a ~2.9-meter whip
> > attached, along with a ~7.7-meter-long conductor connected
> > between the tx chassis and the ground plane. This entire
> > assembly then constitutes the radiating part of the
> > antenna system. (rfry)
> This is true regardless if the transmitter is a SStran,
> Ramsey, or the FCC Certified Rangemaster! Any transmitter
> with any height and a ground will do this, this is why the
> groung lead needs to be as short as possible, it does not
> state the 'tower' or 'pole' needed to be wood, plastic, or
> metal! (Radiopilot)
No, but it does limit the length of the radiator to 3 meters, including the ground lead. It is an interpretation of some Part 15 operators that the only part of the path length to the ground plane that "counts" in the 3-meter length is a short lead from the tx chassis to another conductor leading to that ground plane, such as a "ground wire," a tower, a flagpole or whatever. But that doesn't stop that whole conducting path leading from the tx chassis to the ground plane from becoming part of the active antenna, which can greatly improve system efficiency over mounting the 3-meter antenna at ground level.
> > This setup is commonly installed by people believing it
> > meets Part 15 AM Rules, and the answer you can get might
> > be roughly valid for that configuration. But it also
> > produces 3X more field strength than a ground-mounted,
> > 3-meter Part 15 r-f system, other things equal. (rfry)
> Unfortunately it does meet the rule, otherwise the
> Rangemaster's certification or any other transmitter
> certified by the FCC would have to be revoked! (Radiopilot)
So you believe that the Rangemaster was certified on an elevated mount using a long conducting path from chassis to the ground plane? Probably not, but hopefully Keith Hamilton will tell us exactly what the configuration was. And if it wasn't, then installing/using it in that configuration would not comply with the conditions of its certification.
> So it's your interpretation only and yours truly that all
> must abide? You think other's here don't have the
> engineering knowledge as well to interpret the results as
> well?
My postings are based on engineering equations from recognized sourcebooks, FCC data and field experience. I don't attempt to interpret the results any more than I try to interpret 2 + 2 = 4. Mistakes are possible in my postings, although I try hard to avoid them. I hope that you or anyone who can prove that I have made a mistake will let us all know about it with some factual data giving the reason(s) why.
>> Right now I get 4+/- miles of range with my setup...
>> now THAT goes contrary to what you posted earlier as
>> far as field distances... now how can that be? Could
>> it be that your calculations or calculator you use could
>> be wrong? I'm not the only one getting good range that
>> somehow puts your calculations to question!
I went back to my original post, and modified the efficiency of the radiator to equate to an elevated 3-meter whip on a 1700 kHz Part 15 AM tx, having a ~ total radiating structure of 10.7 meters (35 feet), including the conductor from the tx chassis to the ground plane. Here are the results:
Field Strength > Distance
2 mV/m > 0.287 miles (good signal)
1 mV/m > 0.55 miles (fair)
0.5 mV/m > 1.03 miles (noisy)
0.05 mV/m > 5.6 miles (very noisy)
So yes, depending on your idea of a usable signal, a range of 4 miles or more can be possible from an elevated "Part 15" AM system. But most likely that is the result of using a radiating structure that effectively is more than 3X longer than Part 15 AM defines.
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