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Field Contours

Ai4i

Ai4i

We hear a lot about how far LPAM's can "get out". Can anyone give me some hard feedback, not on how far stations can be heard, but how far in feet or meters a full hundred miliwatts into a properly tuned and grounded three meter vertical radiator over average conducting land in the 1610-1700KHz band can produce 25mv/m, 5mv/m, 2mv/m, 0.5mv/m, and 0.1mv/m. 5.0mv/m should usually provide quieting over skywave signals at night.<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>
 
Well ai4i, part15 AM is not only in feet but miles, I personaly seen the rangemaster do 4 miles "good listenable" up 80ft

and be legal, but I really don't the 1millivolt signal will be at but if this helps at 31/2 miles the signal was 220uV







> We hear a lot about how far LPAM's can "get out". Can
> anyone give me some hard feedback, not on how far stations
> can be heard, but how far in feet or meters a full hundred
> miliwatts into a properly tuned and grounded three meter
> vertical radiator over average conducting land in the
> 1610-1700KHz band can produce 25mv/m, 5mv/m, 2mv/m, 0.5mv/m,
> and 0.1mv/m. 5.0mv/m should usually provide quieting over
> skywave signals at night.
>
 
I knew I would get answers like that, so I will rephrase my question.
How many milivolts per meter could I expect the above described station to produce at a quarter mile, a half mile, a full mile, and two full miles, over a typical range of dry earth conducting surfaces?<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>
 
I, too, would like to know how strong my Part 15 signal is using real-world measurements. As soon as I can get my hands on a frequency-agile field strength meter, I'll be more than happy to pass the information on.

Friend Lee
 
> We hear a lot about how far LPAM's can "get out". Can
> anyone give me some hard feedback, not on how far stations
> can be heard, but how far in feet or meters a full hundred
> miliwatts into a properly tuned and grounded three meter
> vertical radiator over average conducting land in the
> 1610-1700KHz band can produce 25mv/m, 5mv/m, 2mv/m, 0.5mv/m,
> and 0.1mv/m. 5.0mv/m should usually provide quieting over
> skywave signals at night.
>


Ok... here's a try...

The general equation for estimating transmitter field strength is calculated from the equation below:

Distance = (30*Pt) squared/E

Pt= transmitter power in milliwatts or watts

E= reciever sensitivity in field strength (usually 20 uV/m, but you may want to look this up on your portable reciever specs.)

This equation assumes that all the power in the transmitter, 100mw is transferred without loss to the antenna and that the antenna has a gain of unity. The result also assumes there are no losses incurred from transmitter to receiver due to probagation effects as well.

If there are losses due to the antenna not being correctly tuned... a variable of A1 (.005) is multiplied to the above to give the end result.

Distance (m)= (30*Pt squared)(A1)/E

The above can be proved by taking the reciever and going out the 'clear' distance calculated to the transmitter and checking the level of the signal recieved... it would also help if you could tap into the reciever and 'measured' the uV signal itself.

Hope this helps

Radiopilot
 
I was asking about measured field strength from an inneficient antenna over a typical earth ground, not how well different receivers would hear the station from a huge tower at distance over a pure stirling silver path.<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>
 
Hello AI4I

You ask a good question and I for one would also like to see
some technical data directly answering your question.

Someone out there must have the equipment to measure field
strength on a specific AM frequency.
 
I think I found my answer <a target="_blank" href=http://www.part15.us/modules.php?name=FAQ&myfaq=yes&id_cat=4&categories=MWA+Classic%3A+100+milliwatts+%26+more+Part+15+low+power+AM+FAQ>here.</a>

Q: What kind of range can you get from a 100 milliwatt AM transmitter?
A: ...under the best conditions...you might achieve a field strength of 1 mV/m at a radius of 1/4 mile.

So, this station would produce a competitive suburban signal of 5mV/m at about a tenth of a mile and a competitively strong interferrence free metropolitan night signal of 20-25 mV/m at a distance of almost one city block depending on the city.

In other words, place your station on the roof of, across the street from, or in the parking lot of, a highrise condo or apartment building and you should produce a strong signal throughout the property.<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>
 
> I think I found my answer here.
>
> Q: What kind of range can you get from a 100 milliwatt AM
> transmitter?
> A: ...under the best conditions...you might achieve a field
> strength of 1 mV/m at a radius of 1/4 mile.
>
> So, this station would produce a competitive suburban signal
> of 5mV/m at about a tenth of a mile and a competitively
> strong interferrence free metropolitan night signal of 20-25
> mV/m at a distance of almost one city block depending on the
> city.
>
> In other words, place your station on the roof of, across
> the street from, or in the parking lot of, a highrise condo
> or apartment building and you should produce a strong signal
> throughout the property.
>

Would that be one city block in a place like New York, NY, or a place like somewhere in west Texas between Lubbock & Abilene?
 
>
> Would that be one city block in a place like New York, NY,
> or a place like somewhere in west Texas between Lubbock &
> Abilene?
>
I have lived a secluded existance and the only city blocks I have known have been 1/10, 1/12, 1/16, and 1/20th of a mile. From my above refs, probably a sixteenth or a twentieth of a mile.<P ID="signature">______________
Proud 2 B a pioneering satellite radio subs¢riber
Ai4i is always on the trailing edge of technology
______________</P>
 
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