- #1
medwatt
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Hello,
I have built an AM transmitter and now I can only receive signal within just 1m radius of the transmitter. I use a colpitt oscillator to get a carrier of 740khz. For the modulating signal I'm using a 1khz tone from a signal generator although I've also used an electret microphone. I am using the mc1496p IC with the circuit provided by the data sheet as a double sideband suppressed carrier am modulator.
I have tested every stage and observed a perfect sine wave for the oscillator with a peak amplitude of 0.5v. Similarly the modulated signal from the output of the modulator at pin 6 was about the same value.
The carrier signal was successfully modulated because I could see when the 1khz tone signal superimposed on the carrier from the oscilloscope.
My problem is I can only get the transmitted signal at a distance of about 1m which does not make sense and completely defies the who idea of the design.
What I have done unsuccessfully were to use a 1m long wire and use the areil from a radio as a radiating antenna which I connected to the pin 6. I noticed no change when I moved my radio about. I could only receive anything very close to the transmitter.
I hope someone can give me an idea what to do to improve the range so something like 300m which should be actually the minimum distance for AM signals.
Here is the modulator circuit if you wish to see it: http://www.unipa.it/laser/edt/MC1496.pdf
I have built an AM transmitter and now I can only receive signal within just 1m radius of the transmitter. I use a colpitt oscillator to get a carrier of 740khz. For the modulating signal I'm using a 1khz tone from a signal generator although I've also used an electret microphone. I am using the mc1496p IC with the circuit provided by the data sheet as a double sideband suppressed carrier am modulator.
I have tested every stage and observed a perfect sine wave for the oscillator with a peak amplitude of 0.5v. Similarly the modulated signal from the output of the modulator at pin 6 was about the same value.
The carrier signal was successfully modulated because I could see when the 1khz tone signal superimposed on the carrier from the oscilloscope.
My problem is I can only get the transmitted signal at a distance of about 1m which does not make sense and completely defies the who idea of the design.
What I have done unsuccessfully were to use a 1m long wire and use the areil from a radio as a radiating antenna which I connected to the pin 6. I noticed no change when I moved my radio about. I could only receive anything very close to the transmitter.
I hope someone can give me an idea what to do to improve the range so something like 300m which should be actually the minimum distance for AM signals.
Here is the modulator circuit if you wish to see it: http://www.unipa.it/laser/edt/MC1496.pdf
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