Class D AM transmitter from junk parts

[DoaJC_Blogger]

I recently built a Class D AM transmitter mostly from recycled parts aside from the FPGA board for DDS and the MOSFET driver. It was mostly just to see if I could so it doesn't have a filter and you wouldn't want to transmit for real with it. I also used slower Infineon CoolMOS MOSFET's instead of GAN FET's so it gets hot if you try to go above the lower AM band



An article I wrote with more pictures: https://coolsdrstuff.blogspot.com/2026/08/class-d-am-transmitter-build.html

A video of the output on an SDRplay: https://odysee.com/class_d_am_transmitter_test_20260824:5b4a5b7bbbcb57dcf65cd6c86562fb9d0424d61f

[The Mercian]

Good experiment - what sort of power output were you getting before the FETs ran out of steam?

[DoaJC_Blogger]

I don't currently have a way to measure that kind of power but I assume that it was at least 50 watts with the 56-volt power supply since it got the 55-watt sodium light hot enough to start tripping the power supply. I don't think I was limited by the FET's

[Stretchyman]

Looks like youve been inspired by the construction methods from the Class E website!

To measure power, just use a scope and ohms law.

Crusty works!