Re: It appears that we are off the graph
> > > > >
http://www.fcc.gov/mb/audio/bickel/figure8.html
> > > > >
> > > > > Found this calculator and was having fun filling in
> > > > > different values for ground radial lengths, antenna
> > > > height,
> > > > > transmitted power, ERP, and Predicted Field
> > Strength...
> > > > >
> > > > > Any questions about it's use, feel free to discuss,
> > but
> > > it
> > > >
> > > > > will tell you basically how well your signal is
> going
> > to
> > >
> > > > > reach your listeners based on what you do to your
> > > system.
> > > > >
> > > > > Good find, unless you've been there already.
> > > > >
> > > > > Radiopilot
> > > > >
> > > > Hi,
> > > >
> > > > Looks like it is a real stretch for part15 stations.
> In
> >
> > > > Figure 7, at 1500 KHz. you are almost off the graph on
>
> > the
> > >
> > > > left (.05 wavelength for a 3 m. antenna). In Figure
> 8,
> > it
> > >
> > > > is off the graph.
> > > >
> > > > Maybe you saw something I didn't. If so, how did you
> > use
> > > > the information and did it agree with your experience?
>
> > > >
> > > > Neil
> > > >
> > >
> > > Neil,
> > >
> > > I plugged in the numbers as follows for 1550khz (feet &
> > > miles):
> > >
> > > 50 feet height
> > > .0001kw power (.100mw)
> > > 96 feet for the length of the radials (must input that
> > > length for the freq.)
> > > 120 radials
> > >
> > > results should be:
> > >
> > > Predicted Field Strength from Figure 8, Section 73.190:
> > >
> > > (Metric units)
> > > Theoretical Field Corrected Field
> > > At 1.00 kW: 251.891 222.923 mV/m @ 1 KILOMETER
> > > At 0.00 kW: 2.519 2.229 mV/m @ 1 KILOMETER
> > >
> > > (English units)
> > > Theoretical Field Corrected Field
> > > At 1.00 kW: 156.518 138.518 mV/m @ 1 MILE
> > > At 0.00 kW: 1.565 1.385 mV/m @ 1 MILE
> > >
> > > So 100mw looks like I should get 1.385mVm at 1 mile
> > >
> > > I did not look at the graphs as it will not tell me
> > anything
> > > the calculator won't tell me....
> > >
> > > Radiopilot
> > >
> > Hi,
> >
> > Apparently I missed something. I'll take another look.
> >
> > I assume the 0.00 kW is rounded off. 100 mW = .0001kW.
> Is
> > this what you entered or did you scale the numbers?
> >
> > Neil
> >
>
> Hi,
>
> I took another look. Here's what I got when I entered 10'
> height, .0001kW, and1500 KHz.:
>
> "# Tower Height above Base Insulator [ in feet ]: At a
> frequency of 1500.00kHz, the tower height must be greater
> than 32.8 feet tall and less than 442.5 feet tall.
>
> Effective Radiated Power (ERP) [ kW = kilowatts ]:
>
> Average Length of Ground Radials [ in feet ]:
> # Average length of ground radials must be greater than 0.15
> wavelength = 98.4 feet .
>
> Number of Ground Radials [ 90 to 120 ]:
> # 90 radials minimum. More than 120 radials will give same
> result as 120 radials.
> # Ground radials are assumed to be evenly spaced."
>
>
>
> I point out the notes: "the tower height must be greater
> than 32.8 feet tall",
>
> and "Average length of ground radials must be greater than
> 0.15 wavelength = 98.4 feet"
>
> and "90 radials minimum. "
>
> It looks to me that we are off the graph and out of the
> range of the calculator for a typical station. I noticed
> the numbers you entered and would ask if you think a 50'
> height and 96' radials is realistic for a part15 station?
>
>
> Neil
>
Neil,
The 50 foot height is what I was playing with because that is where my antenna is at, the 96 min. length is what the calculator needs and also the minimum 96 radials to perform the calculation. The entry for the power for 100mw is .0001kw and the result is rounded off as you said 0.00kw....
I did not say that this was for part15, only that it was useful to see what a theorectical situation for a part15 100mw signal would be like with that many radials and length, sure not everyone can have 120, 100 ft. radials or 50 foot heights, but they can adjust their system to get the best signal out of the transmitter if some of these rules are followed... some here on this board and the other part15 board have no clue why you need radials, how many, what length, etc. this is just another tool to help them.
It would have been decent of the FCC to provide a similar version for lower power transmitters, but that is not the intent of the FCC to give us those tools that help part15 broadcasters and cause unnecessary backlash from the NAB.
Radiopilot
