Why can't low frequency radiation be used for communication?

Question

Why do we use microwaves for talking in the phone? What impact does the high radiation have?

Answer 1

Bell labs built some devices called carrier bays almost 80 years ago. They used a carrier frequency of about 8000 hertz with double side band surpresed carrier. They filtered out the upper side band, and sent the lower side band over telephone lines. A small amount of the side band radiated, but that did not matter as that low a rf frequency still has near zero uses. One reason we don't use such a low frequency is an efficient antenna needs to be hundreds of miles long. The other reason is only two low fidelity audio channels are possible at that low a frequency. The carrier bay had 4 channels staked up to about 21,000 hertz, Probably the first frequency multiplex system which was used until about 1960.

Answer 2

Low frequency radio can be used for communication. In fact, extreme low frequency (ELF) and super low frequency (SLF) radio waves are used for communication with submarines that are hundreds of meters below the surface. The drawbacks are that these frequencies require huge antennas and the message bit-rate is very slow, which means that it takes a long time to transmit a message.



See the links below for more information...

Answer 3

Two applications of low frequency radio communication come to mind.



1) The US. NBS broadcast WWVB time standard at 60 kilo hz.

2) The US Navy use Very Low Radio to communicate to the Submarine Fleet.