hello! How to calculate or converte Difference in the depth of modulation ( DDM) to uA and to feets or meters. I have only results in wikipedia http://en.wikipedia.org/wiki/Instrument_landing_system but how they calculated that?thanks

I believe that because the DDM's are tones modulated on top of the two carrier frequencies that the tones have to be appropriately commissioned to correctly fit the sideband 150 uA and converge to equal on the centerline. But ultimately it would depend on the amount of power being transmitted to begin with, then the amount of voltage given to the tones as well as the receiver specs. The receiver specs are probably set, but I believe there are many difference between ILS transmitter options. Some countries will govern the radiation pattern, so I don't think all systems are alike.To convert to physical dimensions you would have to take the above information and then plot it out as you do in a survey.