Sine and?

audioguru said:

An inverting opamp is a perfect mixer because one signal does not affect the other. Many signals can be added.

You can add signals then use the added signals to modulate a carrier frequency. That is how radio stations play music and how television signals do it.

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Thank you very much audioguru for your good explanation, this thread is very informative to me.

Can you explain the last paragraph?
As far as I know the AM transmitters transmit a modulating signal with a carrier so that the modulating signal is an audio signal. Is there any other signal inside the modulating signal which would be modulated with the carrier signal too??

If you want a signal like the one posted by on1aag, all you need is two resistors to sum the sine waves from two signal generators.

kchriste said:

If you want a signal like the one posted by on1aag, all you need is two resistors to sum the sine waves from two signal generators.

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No, I know what my friend needs now. He needs a Mixer to ADD those both signals, whether he finds a suitable transducer or not.

wizard said:

Can you explain the last paragraph?
As far as I know the AM transmitters transmit a modulating signal with a carrier so that the modulating signal is an audio signal. Is there any other signal inside the modulating signal which would be modulated with the carrier signal too??

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The carrier is the high frequency signal that is amplitude modulated by the audio. I don't know if AM stations broadcast stereo anymore.

audioguru said:

The carrier is the high frequency signal that is amplitude modulated by the audio. I don't know if AM stations broadcast stereo anymore.

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Yea That's right and I knew it. But you lead me to think that the radio and TV stations transmit an ADDed signal to the modulating signal and the the carrier frequency will carry those summed modulating signals (I.e. the audio and a second signal which I don't know what it is?).

wizard said:

Yea That's right and I knew it. But you lead me to think that the radio and TV stations transmit an ADDed signal to the modulating signal and the the carrier frequency will carry those summed modulating signals (I.e. the audio and a second signal which I don't know what it is?).

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An orchestra is one hundred musical instruments all playing at the same time or an opera is one hundred people all singing at the same time. Their sounds are added together in a mixer and the result is the modulation that modulates the high frequency carrier.

An FM broadcast station has mono audio, left minus right sidebands, a 19kHz pilot signal, storecast background music and some data all added together and the result is the modulation that modulates the high frequency carrier.

A TV station has all kinds of signals added and used to modulate the high frequency carrier.