How do Frequencies NOT COLLIDE?

[frc]

Hello.
I am confused with radio frequencies working...

Consider a radio with 50 Mhz and another radio with 100 Mhz.
I think one of every two signal of the radio with 50 Mhz collide with the other radio with 100 Mhz. Do they really collide?

Please someone clarify this issue, thanks.

 

[andre_luis]

Taking the point of view of a detector, Yes they collide, once all these signals will excite antenna on receiver. However, according to the physics, once these signals are modeled as wave, no mutual interference occurs.


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[Tunelabguy]

Hello.
I am confused with radio frequencies working...

Consider a radio with 50 Mhz and another radio with 100 Mhz.
I think one of every two signal of the radio with 50 Mhz collide with the other radio with 100 Mhz. Do they really collide?

Please someone clarify this issue, thanks.

The two signals add linearly over the transmission medium. They remain added linearly through the receiving antenna and through any linear amplifier that may be connected to the receiving antenna. The signals do not affect each other unless they run into something that is non-linear, like a diode. But in the receiver they are separated by frequency-selective filters before that can happen.

 

[Audioguru]

Is cancellation of two signals a collision?
Two signals that have opposite phase will cancel.
Multipath interference occurs on FM radios. Part of the original signal is cancelled by a reflection from a building or from an airplane.
Audio signals cancel each other too. Stereo speakers playing the same signal but when one is closer to you than the other it makes the signals have opposite phase at some frequencies and they cancel those frequencies. A reflection from a floor, wall or ceiling will also cause cancellation.

 

[dick_freebird]

If you are only, exclusively, concerned about frequency
domain and everything is perfectly linear then the
frequencies are unique and idealized theory applies.

But if your circuit is by nature time-domain, or has some
nonlinear elements, then it may indeed respond to (say)
zero-crossings from either "tone", or may make new ones
by mixing, etc. And the behavior may also depend on the
relative phase of the two tones if it has to do with zero
crossings, crest amplitude or so on.

A lot of work goes on in RF-land to make the assumptions
of linearity and independence of tones, real.

"In theory, there is no difference between theory and
practice. But in practice, there is".

 

[Audioguru]

Sound and RF work like waves in water. When they "collide" they add or subtract their total level.

 

[andre_luis]

All opinions stated above converges to the same conclusion, differing only to minor details concerning to personal model adopted for describe it, but predominantly explains the same thing.



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