[dd_xplore]

To get an idea about radios, I made a crystal radio when I was in 7th grade, I only had few components. The only component I had difficulty in getting was the crystal oscillator (I was living in a rural town).

It was mind blowing when I first heard the audio through IEMs ! It felt magical that this contraption was working without any battery source.

[pkolaczk]

You can use a germanium diode or even Shottky now instead of a “crystal”.

Such a simple radio can be a gateway drug to a very complex and deep hobby. In my case it went like that:

1. Built a simple radio

2. Could hardly hear anything, need to add an amplifier to it 3. Now it’s better but captures a lot of noise

4. Design a filter to select just that one station

5. Now I want to listen to more stations.

6. Ugh, you can’t design a good filter with variable frequency. Enter the superheterodyne world.

7. Now finally got something that resembles a tunable AM radio, but it kinda whistles / hums a lot. Ah, so the mirror image is a real thing?!

8. Need a higher IF to be able to better reject the image before the mixer. Ok, let’s make a double conversion superhet then.

9. Buy a set of ceramic filters and play with them to get the best selectivity.

10. Try to add more amplification only to learn if you go too far you get an oscillator instead of an amplifier.

11. The sound level is not stable. Add AGC.

12. Pick up some stations from 5000+ km away. Nice. But there is some weird distortion. Oh, I’ve been a culprit of frequency selective fading…

Fast forward and now I’m building a PLL synchronized AM product demodulator with a squaring loop for carrier recovery.

Fun. Lot of fun! Wholeheartedly recommend!

[whartung]

There's something to note here.

As someone who's always dabbled in electronics, skimmed and read some books, my primary complaint abot most electronics texts is that they just talk about individual topics: oscillators, amplifiers, etc.

What they never talk about, is putting them all together.

But as witnessed by this list, that's what a radio is. A collection of these "meta" components into a whole to get a better radio experience.

A radio built like this, with individual subsystems connected together, is much more understandable. Many (not all) radio schematics are presented as a whole, rather than the parts, or why you might (or might not) want to change one part or another (not components, but one, say, filter circuit to a different one).

It just seems to me that once you get past some basic theory, starting with a radio, and then systematically taking it apart is a better way of approaching electronics education.

[dd_xplore]

Haha I know! When I was even younger, we had a radio that could recieve SW,AM,MW,FM(in TV range as well). I used to hook up the antenna to various things like wire mesh or tv antennas etc and used to listen to short wave and AM for hours. I even got signals from far away countries, it was really fascinating!

Also I had seen some recon antennas in a certain campus (can't say much about that) when I was a kid. Those were like long wires hanging from towers. I believe they used to receive/decode SW/AM signals from far away. I realised this much much later in my life. But fascinating nonetheless. And adding to all these is SDR! That's a whole different thing.

[jacquesm]

> You can use a germanium diode or even Shottky now instead of a “crystal”.

Or a razor blade or a piece of roofing lead and a needle.

[Aloha]

I have used a synchronous AM detector once in a radio, its a game changer for listening to shortwave.

[immibis]

The crystal radios I know don't have crystal oscillators - the word "crystal" refers to the diode.

[gtsnexp]

https://www.youtube.com/watch?v=-GxL13rid1w

[dd_xplore]

Perhaps I'm getting confused cuz this was long back. But I think it was a oscillator for sure...

[kragen]

Crystal radios don't normally contain crystal oscillators, which do require a battery source. Perhaps you mean a crystal rectifier.

[dd_xplore]

Yeah perhaps I'm confused cuz this was long long back.