💾 Archived View for zaibatsu.circumlunar.space › ~solderpunk › phlog › crystal-radio-in-2018.txt captured on 2020-09-24 at 01:49:11.
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Crystal radio in 2018 --------------------- Since I enjoy shortwave DXing and enjoy tinkering with electronics, it's perfectly reasonable to expect that I'd enjoy homebrew radio projects. And I'm definitely *interested* in it in principle, and every few years the interest gets strong enough that I start searching for schematics and thinking about things to do. But I'm inevitably put off pretty quickly by how much trickier sourcing parts is compared to other projects I could undertake, and how much extra mechanical faffing is involved. If you want to play with microcontrollers, it's ludicrously easy. You go to some nice big serious supplier's website, Mouser or Digikey or RS or whoever, and you use whopping big powerful parametric search systems to find parts from established brand names, you buy them for *cents* per part because ICs are dirt cheap, and everything turns up in the same box. But if you go to any of these places and try to find a ferrite rod, or a variable inductor, or a variable capacitor that varies over hundreds of picofarads, and you'll either find nothing, or you'll find something obscenely expensive, because these things are now totally obsolete and super niche. You're more or less forced into buying random surplus parts from people on eBay, probably buying from multiple buyers to get the best price and everything. There's a healthy chance you're going to end up having to wind some precise number of coil turns yourself on some kind of former. You won't have much luck prototyping stuff on a breadboard, because radio is *literally* voodoo and all sorts of irritating physical world stuff like parasitic capacitance which you can often totally ignore for low speed digitial projects will just totally ruin your day in the RF world. It's just in general more expensive, involved, and fiddly, and I usually end up abandoning the idea after a few days. Recently, though, for whatever reason it has taken a stronger hold than previously and I have actually bought a crystal radio kit. Yeah, this is kind of super-basic and boring, but I figured it's a very low effort way to scratch this recurring itch and see if it takes hold. Because it's a kit I'm getting all of the parts in one box without spending days sourcing stuff. If I decide I want to get more serious I can cannibalise most of the parts for a transistor TRF design. If nothing else, I tought it would be a little nostalgic. I had a crystal radio as a kid, one of several of those projects where you used tight springs sticking vertically up out of a plastic board to join parts together. I very clearly remember listening to it in bed one night and hearing a broadcast of mission control radio trafic associated with a shuttle landing - no idea which one. Obviously this was being rebroadcast from an Australian AM sation, probably the ABC, but I'm pretty sure that in my young mind I imagined that I was hearing this live and direct from the shuttle itself, as ridiculous as this obviously is. While I was initially pretty excited to receive the kit, I've been doing some reading and thinking since then and yesterday it occurred to me to check something and I made a horrific discovery which has dented my enthusiasm. The broadcast AM band has more or less been totally abandoned in Finland. There's a single 100 Watt station in Tampere and *that's it*. I can't receive that station in my home with my Tecsun PL-310ET which is, you know, an *actual* radio with batteries and transistors (I might try for it in a forest at night sometime, but it still seems unlikely). This crystal set is going to be totally useless, as designed. Apparently in 2018 in this part of the world, there is just nothing to listen to on AM radio. The kit is probably not a total write-off (and even if it is, it was cheap enough that I won't lose any sleep), because there is nothing specific to the AM broadcast band in a crystal radio, and by removing some windings from the coil of the tuned circuit I can maybe rejig it for shortwave or something, or maybe even some amateur bands, although I think most hams are using SSB these days, which is no good for a crystal set. But regardless of all this, I am really strangely shaken by this discovery. It didn't even occur to me to question before I ordered this whether or not there'd be anything to listen to on it. I mean, of *course* there's shit on AM radio. I still can't quite accept that there's not. I'm not sure why, I have no trouble coming to grips with the fact that casette tapes and landline phones and countless other mainstream technologies I grew up with are dead. For some reason I can't put my finger on, the death of an entire broadcast band feels massive. Maybe my perception is warped because I listen to shortwave, which I think of as roughly 10,000 times more niche and less commercially viable than *any* other kind of radio, yet I still have no trouble finding stuff to listen to on it, so the fact that something