250mW 40 Meter AM Transmitter

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Post by Admin on Sun Dec 02, 2018 7:40 pm

Hi Joy,
I will get on with this one during the week in my lunch breaks.

BR Harry

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Post by dare4444 on Thu Nov 29, 2018 11:25 pm

Yes Harry you can.

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Post by Admin on Thu Nov 29, 2018 10:24 pm

Hi Joy,
This looks like a nice circuit. I will look more at this after the 160mW TX project is finished.
But it looks really interesting.

If you want I could add a short description about it?

Best regards from Harry - SM0VPO

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Post by dare4444 on Thu Nov 22, 2018 7:27 pm

Few years back I designed this AM transmitter for 7MHz. It uses an IRF510 in the final which is series modulated by a TDA2003 audio amplifier chip. I don’t have the prototype with me but good modulation characteristics were obtained and audio was load and clear. Another ham more than 70Kms away picked up the signal. The IRF510 is being driven by a TC4422 MOSFET driver IC. The oscillator is a single transistor PN2222A or BC547. The crystal should be selected for the 40 meter amateur radio band. Output power was in the order of 250 milliwatts and IRF510 did not need a heatsink. An electret microphone gave good audio reports.

Schematic https://ibb.co/fvjkfV

Include this circuit in your visitors section if you would like and not under Transmitters section as it lacks some documentation.


Last edited by dare4444 on Fri Nov 30, 2018 2:40 pm; edited 1 time in total

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