I've been having a play around with some SDR software and messing with different modulation schemes over the last few months as a sort of
side/hobby project related to my endeavours in ham radio. I've managed
to make a working transmitter for AM modes like shortwave and
mediumwave/AM broadcast band radio, as well as AM derivatives like the
VSB envelope used for analog television's picture modulation.

If anyone is interested in a flowgraph, python script, or C++
implementation, let me know. I have tweaked it for ham radio uses (so a narrowband voice-grade DSB AM envelope with carrier), but if you wish
to use it for part-15-compliant uses for old radios where you don't
have any good AM stations around then go right ahead. It should be
fairly easy to adjust bandwidth by just adjusting the oversampling
factor and the audio filtering. Two times the highest audio frequency
gives your AM bandwidth, if you didn't know, and two times your desired bandwidth gives your minimum RF sample rate. I sample my audio at 48000
samples per second, so multiply that by what you like to get the needed
RF rate or higher.

AM has always been a point of fascination for me, it's so simple yet
very complex in the RF space. And it can sound a whole heck of a lot
better than most AM stations make it sound. Remind me to show you the
wideband broadcast station near me sometime, it sounds pretty damn
close to mono FM with a radio that has a wide enough filter.

That's all for now, enjoy my latest nerd obsession. :)

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-nkeck72 (Mac Plus)