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# multiplier

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#### electronspeed

##### New Member
How 2 signals can multiplies using transistor as active component, say the 2 signals to be multiplied are one with frequency=1KHz and other with freq=1MHz.

#### Papabravo

##### Well-Known Member
You need to understand a circuit called a doubly balanced mixer. It multiplies two signals together and produces components at the original two frequencies, (1 kHz, 1 MHz.). It also produces components that are the sum and difference of the two frequencies. These are called the upper and lower sidebands. They are at 1.001 MHz. and at 0.999 MHz.

Bob

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#### Papabravo

Give Mr. Bob Scott a kewpie doll, a long cigar, and...oh say $64,000. Actually I know you know the answer, I was kinda hoping the OP might make the effort. Last edited: #### Njguy ##### Member You need to understand a circuit called a doubly balanced mixer. It multiplies two signals together and produces components at the original two frequencies, (1 kHz, 1 MHz.). It also produces components that are the sum and difference of the two frequencies. These are called the upper and lower sidebands. They are at 1.001 MHz. and at 0.999 MHz. Now, for the$64,000 question -- what happens when you run the upper sideband at 1.001 MHz. and local oscillator of 1.000 MHz. through the multiplier? What comes out?

Like the pulsating of two sounds just barley out of frequency I'm guessing.

#### Nigel Goodwin

##### Super Moderator
Like the pulsating of two sounds just barley out of frequency I'm guessing.

Hetrodyning (or Heterodyning) is the term you're looking for.

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