Difference Between High Frequency Signals & Low Frequency Signals

[AL2448]

What is the difference between high frequency signals and low frequency signals in terms of the distance that can be travelled by the signal, the power required to transmit the signal (for a certain distance), and susceptability to interference (EMI)?

 

Thanks!

[Cap'n Refsmmat]

By "signals" you mean radio signals, I presume?

 

Well, I suppose you can generalize. FM radio, with a high frequency and shorter wavelength, only has a range of a hundred miles or so (barring weird atmospheric conditions.) Shortwave radio, with a lower frequency and longer wavelength, can travel thousands of miles because it skips off the ionosphere. And the US Navy uses incredibly low frequencies (huge wavelengths) for communicating around to world to operating submarines.

 

As for power required and interference, I don't know. Interference usually depends on the way you modulate the signal, not solely the frequency.

[YT2095]

you also have to factor in harmonics when considering Earth based transmissions along with time of day and solar activity (seasons).

higher frequencies will pass through the ionosphere and off into space where they will travel onwards forever, lower frequencies will bounce off it and be reflected downwards again at an angle, often doubling the line-of-sight distance, this is called propagation or Skip.

 

this may help: http://en.wikipedia.org/wiki/Radio_propagation

[dwella]

The low frequency range being lower than the high frequency range, wherein said splitter applies a low-pass filter to the transmission signal to generate the low frequency signal, wherein said splitter determines a difference between the low frequency signal and the delayed transmission signal to generate the high frequency signal, a first coder for deriving a first coded signal within the first frequency range from the low frequency signal, and

a second coder for deriving a second coded signal within the high frequency

range from the high frequency signal.

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dwella

Edited September 17, 2008 by YT2095
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