@Cyberwiz.Yes, technically, FM is better than AM. A radio station piggybacks radio signal to broadcast over a another signal (called carrier, and the process called Modulation). A receiver demodulates the composite signal to seperate the main signal from the carier. In AM broadcast, the varying quantity is the Amplitude, whereas in FM boadcast, its frequency. In both cases the composite signal is susceptible to degradation when it travels far. The difference is that, degradation in apmlitude is more prone to loss than the frequency. Hence, the loss in quality in case of FM transmission is much less than in AM. Obviously, FM generally produces much better sound quality than AM.@netfreak>> I don't think Line of sight goes to 100 or 200 KM. Radius of Earth is 6378.16 KMs. 100 KM divided by 6378.16 KMs is 0.015678 %. Flat enough? 100 KMs is perfectly LoS, when it comes to Earth.>> 1. It has stereo transmissionWhere did you get that from?FM is just a broadcast technology. Whether a radio station uses it for Mono broadcast or stereo, is entirely upto the radio station. Tomorrow, Some radio station may want to broadcast Dolby encoded 5.1 program material in 2 channels stereo over FM. Will that make FM a 5.1 broadcast system?FM is not stereo. FM is usually stereo. It is stereo, if: (1) You are tuned to a station broadcasting in stereo (2) You have a stereo capable receiver (excuse the 35 buck handsets) (3) You have good enough reception for the demodulator to demultiplex the stereo signal. If not, it will act as if the signal were Mono~ Ranjeet Rain