Ron H said:Pardon me for shouting, but YOU DON'T NEED SINGLE SIDEBAND! It would only make your job more difficult. SSB removes the carrier from the signal. You would have to reinsert it in the receiver. How would you do that?
If you do transmit DSB, once DSB has been received, SSB is totally useless in the receiver. Are you under the inpression that one of the sidebands is the final output of your receiver? It is not. You must demodulate the received signal, and to do that, you need the carrier.
The purpose of SSB is to conserve power and bandwidth in a transmitted channel. If you are transmitting ultrasonically, channel bandwidth is unimportant.
Go to Google and read everything you can find about SSB.
epilot said:ok, i have buld the second circuit and it seems it works(i can see amplitude exchanges onmy oscope with modulated signal as input and a 40kHz square carrier wave generated with a 555 ic)
anyway i have a square wave in the output(hope it works instead of a sine wave)
ok i think you want me to removecarrier and one sideband in the reciever, and use from a DSB for the transmitter, is this correct?
Nigel, i think it is possible making a SSB using only one high or low pass filter, if so,why you are saying that "is a VERY different technique"?
i want to amplify the output of 1496, this means i want to amplify the AM signal, i want to use from an amplifier IC ans since i have some of LM3875(it can Handle more than 50W)i want to use them, what is your idea?
i connect the input of amplifier IC to output of 1496 IC and the ouput of amplifier goes to ultrasonic transmitter,is this a good idea to improve the output of 1496 IC?
Nigel Goodwin said:What are you using for a de-modulator anyway?.
audioguru said:The modulator IC isn't perfect. A little amount of the modulating signal goes to its output.
Maybe your power supply needs better regulation.
Maybe your amplifier produces even harmonics distortion which attenuates one polarity of the modulated waveform. So the amplifier is performing like an AM detector.
The lousy quality of AM produces noises. Noises are amplitude changes. AM is amplitude modulation.epilot said:i have the problem yet with alot of noises.
Maybe the audio input level is too high for the MC1496.if i cut the generator output wire, i have the clear voice(loudly)on the output of 1496
Ron H said:OK, here's my suggestions: Set the modulating voltage (the information signal) to 0.5V peak-to-peak. Change Re to 2k. Set the voltage on pin 4 to 3.8V by adjusting the 10k pot. You should get a waveform similar to this one. I used a 1kHz modulating frequency. You can make this whatever you want. Note that by varying the voltage on pin 4, you can change the depth of the modulation.
audioguru said:You hear a weak audio voice signal from the ultrasonic transducer that has 40kHz AM modulation because the transducer has even-harmonics distortion and is acting like an AM demodulator.
The 1496 also has even-harmonics distortion that could be cancelled if you use both outputs as a balanced signal to the amplifier.
Ron H said:Your "square wave" carrier oscillator does not produce a 50% duty cycle, which could cause problems. I would change the circuit, or double the frequency and then divide it by two with a toggle flipflop.
If the transducer moves in one direction a little more than in the other direction then it has even-harmonics distortion and its average movement follows the modulation.epilot said:i can not understand why and how it acts like a demodulator?!
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