If I have an SSTran AMT3000 that puts out 100 mw, and if I know somebody who could increase the power up to 500 mw, how far could I reach with mediocre soil?
Disregarding the obvious fact that this would be illegal under Part 15, the answer to your question is that no one but you can really answer this question. It really depends on your particular location, antenna, ground system, etc. This is true, even at 100mW.
If I remember correctly, if you were to increase the power 4x, you would double the range (theoretically). Someone correct me if I'm wrong. This assumes that everything else in your installation is the same.
It is very unlikely that your SSTRAN unit puts out 100 mW. The 100 mW number usually refers to the maximum power allowed to the input of the final RF amplifier for Part 15 operation.
At a given distance the field strength in volts per meter is proportional to the square root of the power.
So, if nothing else changes, except power, going from 100 mW to 500 mW is a 5 times increase in power from which I would predict that your range will increase by a factor of 2.23. To gauge your range, take your range at 100 mW and multiply by 2.23.
I also predict that you will be exceeding the legal limit for final RF stage input power by a factor of five. The choice is yours.
Neil
If you are bent on increasing the coverage area of your station, the only legal method currently is multiple transmitters. The transmitters are spaced in such a way as to "beat" frequency with each other. This also requires properly phase correcting the audio. You could visit the Rangemaster site for a better explanation.
Please understand, the direction your questions are taking will set you up for a visit from the FCC. The FCC won't be the people to "turn you in". It will be your friendly hometown AM/FM broadcaster. They don't like the competition. The smaller the town, the more critical this issue becomes.
By using multiple transmitters, with improved ground radial systems and assymetrical modulation (125% positive peaks) from a real AM audio processor, you can become a credible radio station for listeners. Being a "pirate" radio station will not attract listeners long-term or enhance your station's credibility in the community. Stay legal.
By the way, who cares how far the signal goes. If the folks who can potentially hear your station already don't listen regularly, you have a bigger problem anyway. Build listeners with the signal you have now and then let listeners drive the expansion of your station. It makes a lot more sense, doens't it?
Marshall Johnson, Sr.
Rhema Radio - The Word In Worship
http://www.rhemaradio.org
The field strength at a given measuring location will change by the square root of the change in radiated power (other things equal).
However a power increase does not "move" a given field strength value further away by that same factor, because in addition to the inverse distance lossses, ground losses continue to accumulate as the wave propagates over the surface of the earth on that longer path.
Here is a re-post of my earlier data for a Part 15 setup "in Alabama," showing the additional distances for 500 mW of applied power from that near-perfect system:
INPUT DATA:
Loading Coil Resistance ~2 ohms
Frequency = 1,600 kHz
Conductivity = 3.0 mS/m
RESULT:
Contour level > Distance with 80 mW > Distance with 500 mW
5.000 mV/m > 0.0322 miles > 0.0805 miles
2.000 mV/m > 0.0805 miles > 0.1677 miles
0.100 mV/m > 0.9448 miles > 1.785 miles
So for example instead of the 0.1 mV/m contour being extended by the square root of 6.25 (2.5X), it is extended only by ~1.89X.
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Follow Marshall's advice. Stay at or below 100mw and stay legal. The last thing Part 15 operators need is to be labeled as "Pirates" because some operators decided to run much more power then is legal. The FCC can take away the Part 15 rules if people don't follow the them, and that hurts everyone. Just don't do it.
If you want a better range, webstream via Live365, SHOUTcast, or another service.
Sorry if I seem harsh, but I don't want a good thing to go away.
Yours Truly,
Mark Shannon
AM 1690 WOQ, Omaha's Fun Station
The last thing Part 15 operators need is to be labeled as "Pirates" because some operators decided to run much more power then is legal.
To clarify this a bit -- a Part 15 AM tx operating with 100 mW DC input power still can be part of a "pirate" operation if it is used with an illegal antenna, even though the tx may have a label saying it is Part 15 certified, and an applicable FCC ID number.
If the tx was FCC-certified, that certification was based on the antenna used in the certification process. Using that tx with a different antenna voids that FCC certification. Compliance with Part 15 then is the responsibility of the user.
Using a tx with 100 mW input power with an antenna system having a radiating length longer than the total 3-meter legal length produces the same result as increasing the power output of a 100 mW tx used with a legal-length antenna. This is the common end result of "elevated" Part 15 AM systems.
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I'm talking strictly about power levels, not antenna length, as this post is about.
Yours Truly,
Mark
AM 1690 WOQ/Omaha's Fun Station
I'm talking strictly about power levels, not antenna length, as this post is about.
But the FCC doesn't care whether or not your excessive field strength is related to your excessive tx power alone, to the excessive radiating length of your antenna system, or to both of these in some combination.
You may get nailed, in each case.
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