Our teacher want to make us a long range AM Transmitter. I try to search it on the internet and I found one simple AM Transmitter circuit in YouTube channel Afrotechmods. But I try this and not working with this OP AMP TL072. Found the revised version and my AM Transmitter is now working using LF347N. But the range is very short (about few centimeters) and our teachers want a long range AM Transmitter for our final project. I add a fixed inductor 220uH and the antenna used is 1 meter stranded wire but not improved at all.

This is my schematic diagram I create: AM Transmitter Schematic Diagram

My Can I make a long range (100 meters or more) AM Transmitter using this circuit?

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    \$\begingroup\$ Welcome to EE.SE. You might edit your question to add details of your antenna and your detector (e.g. an AM radio). 100 m isn't long range in AM radio! Half-way around the world is! \$\endgroup\$ – Transistor Oct 2 '17 at 23:35
  • \$\begingroup\$ The length of the antenna will be an important detail. Add this information and again add the receiver information into your original question so that all the information is in one place. \$\endgroup\$ – Transistor Oct 2 '17 at 23:46
  • \$\begingroup\$ May also want to consider using a ferrite rod or loop antenna \$\endgroup\$ – sstobbe Oct 3 '17 at 1:38
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    \$\begingroup\$ That is one of the worst designs I have ever seen. It's a miracle that it works at all. Don't just copy any old rubbish you found on Youtube. Do some proper research to learn how AM transmitters work, then find or design a circuit that uses established principles. \$\endgroup\$ – Bruce Abbott Oct 3 '17 at 3:30
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    \$\begingroup\$ As with your other question, electronics.stackexchange.com/q/334698/4512, we are not here to do your homework for you. \$\endgroup\$ – Olin Lathrop Oct 16 '17 at 11:53

This isn't a direct answer to your question, but too long for a comment.

You are going about this completely the wrong way. Your teacher assigned you something so that you will learn about it. You are not only trying to get away with just copying something, but in addition, you clearly don't understand the fundamentals behind what you are trying to do. This is not how to learn electrical engineering, or anything else for that matter.

The circuit you happen to bump into is crap, but that's really beside the point. You need to understand what a AM transmitter needs to do, and how a circuit can accomplish that.

Learning why the circuit you have is a bad example might be useful, but you're not really asking about that. You just want someone to hand you a finished result. That's not how things work.

Either get serious about learning electrical engineering, or find something else to do and stop pretending.

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    \$\begingroup\$ @Chr: You're not listening to anything I'm saying, so I'm giving up. \$\endgroup\$ – Olin Lathrop Oct 16 '17 at 11:52

Try winding wire around a toilet roll, and join a variable capacitor in parallel with the coil. connect the output of the transmitter to one end, and the earth output to the other. Connect your antenna and ground, and tune till you get a strong signal on your radio. Experiment with different numbers of turns if you can not peak the signal. You might be surprised by the result. Stumbled on this when I used to play with little circuits when I was about 9 years old; nearly 60 years ago. The toilet roll will act as an aerial tuning unit, which makes the transmitters think that it is seeing an aerial of the correct length, or impedance. You must have a correctly tuned aerial for any transmitter to work to the best of its capability. In more more powerful transmitters, a badly matched aerial can burn out your output transistors.


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