160 meter AM using tuner.

I started to build a simple 160 meter AM transmitter using a old tuner. Target output is 1 Watt.

The plan was to build the complete transmitter in the tuner. Unfortunately It did not fit in my tuner. So I put it in a old printer switch box.

The design is straight forward. The signal out of the tuner is amplified by a few bc547 amplifiers. then that signal is used to drive a 4427 mosfet driver. This driver drives a IRF510. It works in Class D. The output is filtered by a 7 element Lowpass filter. Modulation is done by a darlington transistor. That works as a modulatable power supply.

At this stage it is functional but there is room for improvement. Modulation depth is 75 procent maximum. Harmonic suppression can be improved. Especially between 15 MHz and 25 MHz. The signals are 40 db below carrier. That is probably good enough but I think it can be improved easily.