Practical Radio Circuits (2003) [pdf]

A friend and I have been trying to build an AM radio. We got a few working, like the basic "crystal" (germanium diode) one with an earpiece, generally picking up 1 or 2 stations very faintly. Then some attempts with an AM radio IC (TA7642), some that use a couple diodes and LM386 op-amp but they're generally terrible, if they work at all. It seems that following random schematics off the web or a youtube screenshot doesn't work very well.

I do have an RF design book I haven't started (by Chris Bowick) as well as this PDF now, which should be even more practical, so I'm hopeful I can figure it out. I also have some test equipment such as nanoVNA, tinySA, and an oscilloscope which makes it possible to get visibility into how stuff behave beyond "I don't hear anything; no idea what's wrong." I was able to see how the tank circuit was behaving as you tune it.

You can pick up a pretty reasonable amount of radio signal with the right length of wire and a properly tuned LC circuit tank.

I didn’t believe it until I tried it, but it’s a surprisingly good first pass at an FM frontend.

Some thoughts - this is a good overview of how stagnant the hobbyist state of the art was 20 years ago. You could probably have built all of these circuits with the those exact parts in 1973. Pretty much everything in this collection but the superhet and direct-conversion receivers is obsolete and was at best obsolescent at the time. You can think of a typical SDR as a dual-conversion receiver with a conversion stage in the digital domain. Superregens were used in remote controls right up through the turn of the century, but by the time this was written no one was designing new ones. I saw a TRF front end on a commercial ultrasound device in that era but it was not typical.

Many RF transistors are no longer available in through-hole though you can probably find small quantities for hobby projects. The msph10 is long gone. And good luck sourcing dual-gate mosfets even in smt. Infineon might still make a couple.

As a digression, it does make me think TRF receivers are probably a better learning tool than the my-second-radio regenerative receiver. Crystal radios, of course, are pure magic and it’s sad that so few people get to build them as kids.

The regenerative receiver, followed by the superheterodyne receiver? Edwin Howard Armstrong might be the man who fell to earth.

Loved this practical guide publication format. Anyone know other magazines like this Everyday Practical Electronics?

i'd love to see some grassroots-powered clandestine para-web running at least partially on radio. obviously such a project would either immediately or at some point face the usual issues like: spam, cp etc. that's why i believe such a network would have to be slow. it would have to be so slow (and just fast enough) for text-based communication and simple protocols. and i mean text as in < 1kB ... not sufficient for transmitting sth like base64(videoclip). that would be so cool.

where can I buy new these f&*(( headphones