I’m a little confused about how satellite communication works. My understanding is that there is a Line-of-sight wave from the user to the satellite and then a Line-of-sight wave from the satellite to the destination. I also have heard that whether a radio wave behaves like a ground wave or Line-of-sight wave depends on the frequency of the wave. It’s not intuitive to me why this is. It’s also not intuitive why we don’t communicate with ground waves. Is it because they are slower in spite of the fact that you’re substantially increasing the distance that the data has to travel?
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Ground following waves have low frequency, we talk about 3MHz and below. So you have a total spectrum of 3MHz to transmit data it will be shared by all radio waves. The lower the frequency the better they floow earth
WiFi uses 20MHz or multiple of 20Mhz to transmit data so datarate you can manage at 3MHz is quite low.
The signal is also attenuated with distance because earth’s surface is not a preferred conductor. So you need high power. The signal will also travel a lot better of the sea than over land.
The required antenna size also depends on the wavelength and they will be in kilometers for low-frequency waves, antennas need in that size order too.
Ground waves have been used and are still used for long-distance communication. There was cross-Atlantic radio transmission for Morse code messages starting in 1901. The had high power, huge antennas and low data rate.
Because there are better alternatives it is seldom used today, There is still limed usage for communication with submarines that can receive signal underwater. Sometimes signals are sent that way to.
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