Good day,

I have been confused about this term for a long time and praying someone can explain it to me to understand.

What is the center Frequency of a signal ? Is it the same thing as a carrier frequency that carries the message signal ? Is the center Frequency the frequency where an unmodulated signal is transmitted and received on ? What role does the low and high cut off frequencies play in the signal ?

 

The term's meaning depends upon what type of signal your are referring to.
What type of modulated signal?
What high and low cut-off frequencies?

 

Usually, we are assigned a channel from our local Telecommunications Authority. It has for example: Channel 1 with a Go Center Frequency (10715MHz as an example) with a channel bandwidth of 40MHz.

This channel assignment has to be the range of frequencies that the message signal can contain ( 10715+20Mhz & 10715-20MHz). The center Frequency of 10715 is the frequency that the message signal is transmitted on. This still has to be modulated with a carrier frequency to be transmitted ?

Please let me know if my understanding is right or where did I go wrong/confused about. Appreciate the help!!

 

Okay.
So the center frequency is the middle of the channel and is the carrier frequency.
The bandwidth accommodates the frequencies generated by the modulation signal.
This is assuming that this is standard double-sideband AM or FM modulation system.

 

Okay.
So the center frequency is the middle of the channel and is the carrier frequency.
The bandwidth accommodates the frequencies generated by the modulation signal.
This is assuming that this is standard double-sideband AM or FM modulation system.

Great explanation. Let me see if I have down now. If I purchase a microwave radio and receive the assigned licensed frequency for the microwave radio from the telecommunications authority, the local oscillator in the radio will produce a carrier frequency to match the center Frequency of the channel provided to me from the telecommunications authority ?

When the LO produces this carrier frequency it will mix with the message signal and all modulated signals will have a frequency between the low and high cut off frequencies of the channel to be transmitted and received ???

 

Can someone validate if what I said is correct ? Thanks?

 

What you are describing is a baseband converter which converts the carrier frequency directly to the modulation frequency sidebands.
More typical is a superheterodyne converter which uses a local oscillator to convert the frequency to a fixed IF frequency where the bandwidth filtering occurs.
Without knowing what radio you are buying, I can't say which technique it uses.

 

Here https://www.sigidwiki.com/wiki/ATSC_Broadcast is something that's really wierd. ATSC modulation. Here center frequency is the )upper-lower)/2 and it's not even shown. I do have an ATSC tuner that does use that center frequency. User display is typically virtual channel number, but when adding a channel, center frequency is used.

You can also have modulations that can have their own pieces with a "center frequency" such as FM stereo.