The crystal radio...
When I was about 8 years old, my dad helped me build a crystal radio. If you're not familiar with these little devices, here's a good description.
This happened in a very roundabout way. It all started with the small library – a few hundred books – in our home. Some of these books were quite old, dating back to the 1860s or so. I know they came somehow through my dad's parents, but I'm not sure of their precise provenance. Some of those books were my childhood favorites – Uncle Wiggly, old editions of the Wizard of Oz, and so on. There was, amongst these books, a few that were directly aimed at small boys. Camping and outdoorsmanship, small boating, and one from 1919 that described how to build a crystal radio. I remember that date because it amazed me then that way back in those prehistoric times they actually had radios. The descriptions in the book were irresistible to me – build this radio, and you could hear people all over the world, and even the sounds made by the Sun. I asked my dad some questions about that book, as it had quite a few words I didn't understand.
Years later I discovered in a conversation that my dad had noted my special interest in that book, and in radio in general. He knew just a tiny bit about radio, things he picked up during the war – and he had built several crystal radios himself. When I wasn't around, he picked up that book to see what it would take to build the radio. He was surprised at the complexity of it – it was far more sophisticated that the simple ones he had built. But it all sounded doable except for two parts he didn't have access to: a pair of radio headphones (what we would call today a sensitive, high-impedance headset) and a galena crystal. However, he had an idea how to get both of those: his older brother, my Uncle Earle, was an electrical engineer whose hobby happened to be mineralogy. So he wrote to Earle (who lived in northern New Jersey) to see if he could help. Earle posted back a package with a very nice pair of radio headphones and a superb little example of a galena crystal.
On a cold wintery day, probably the winter of 1959-1960, my dad asked me to come down in his workroom in our home's basement. There he had a cardboard box with all the parts I would need to build the exact radio described in that book. I couldn't possibly have been more surprised by this! I had not the slightest inkling that he was interested in helping me build that radio, and really, I didn't think it would even be possible for me to do it. Some of the radio's parts sounded exotic and expensive to me (a galena crystal? surely that was at least two bazillion dollars!), and the whole thing was way, way more complicated and involved than anything I had ever built myself. Living on a farm, with well-equipped workshops and reasonably skilled – if utterly utilitarian – craftsmen around me, I was comfortable with the idea of making my own things in a general way. But something like this? I figured it was about on the level of Swiss watchmaking, far beyond anything I could do.
My dad, though, was very encouraging about attempting it. He told me how he had built several crystal radios when he was a kid, and that they weren't really as difficult as I thought. He was certain I could do it, if I just applied myself – and he'd be there to help me with the parts I didn't understand. Basically he said “Go for it!” – and supplied me with the means. At the time, he didn't tell me where the headphones and galena crystal had come from; he just presented me with them matter-of-factually, and told me to be careful with them, as they were valuable. Then he left me alone with the box of parts and the book.
The first thing I did was to sit down and inventory the stuff in the box. It really was all there – every last part called for. The headphones I marveled at: hard, polished Bakelite earpieces held in a cloth-covered spring frame than was so adjustable that I could make it fit my little head. They had a 5 or 6 foot long cord made of very flexible wire covered with cloth, and terminated in a big thick brass plug – what we'd call today a 1/4" phone jack. At the time I looked at that piece of gear as I might today look at a Mercedes car – an unattainably expensive object that had unaccountably made its way into my hands.
I think I read that book cover-to-cover four or five times before I dared pick up any of the parts to actually start building the radio. The book made an interesting assumption that was actually considerably out of date even then: that you couldn't just go out and buy the radio's components. It assumed that if you needed an inductor (which the book called a “coil”), you'd have to wind it yourself. Similarly, if you needed a capacitor (fixed or variable, then called “condensers”), or a resistor (“attenuator”), or a point junction (“cat’s whisker”), why, you'd just have to make the darned thing. Today that seems nearly insane, as you can easily buy all these components (much better versions, actually) for just a few cents each. But back then, those components cost much more than that, and were much harder to obtain – and I certainly learned a lot by making all those things.
I don't remember how long it took to finish that crystal radio, but in my foggy memory it was weeks and weeks of work. Very satisfying work it was, too. I wound coils of magnet wire around cylindrical oatmeal boxes and pencils. I remember that making the “taps” on these coils was especially tedious, requiring careful scraping of the enamel around a tiny little loop, to make a place for the alligator clips to hook onto. I made fixed condensers by making alternating layers of waxed paper and aluminum foil, wrapping them tightly around a pencil, then annealing them in boiling water. Making the connections to those homemade condensers was really hard, as the aluminum foil was so fragile. I made variable condensers by making blades of old aluminum sheeting scrounged from something or other, like the photo here only much, much cruder. I made the attenuator (like a volume control) by filing notches in thin steel wire, and making them extra thin with emery paper. When I had all the components made, I mounted them all very carefully to a small piece of board, and made little “front panels” so I could make markings for the various settings of the variable condenser (used for tuning the radio to different frequencies, or stations).
All along the way, when I ran into something I didn't know how to do, my dad would pitch in to help me. I remember a few things in particular: he helped with the annealing of the fixed condensers (which my mom wasn't too excited about, because we were doing it on her stove :), with the measurement of the wire for the biggest of the coils (the book specified the tap distance in “turns”, and the idea of fractional turns was beyond my arithmetic knowledge). He also helped with mounting the rotating part of the variable condenser – this required some very careful and precise drilling and gluing. In retrospect, that's one of the most surprising bits – because one thing my dad couldn't claim to be was a meticulous craftsman. He built things the way farmers do: functional, not beautiful. Close tolerances? He never heard of them. Strong he could do. Pretty, not so much. I can still remember the way his face got all screwed up in concentration as we drilled the holes to hold the variable condenser shaft...
The most challenging bit of all, though, was the galena crystal and its “cat’s whisker”. The book called for the crystal to be mounted with one wire clamped tightly to one end, then cast into a small tin (we used a sardine tin) with plaster-of-Paris. Then the hard part – mounting a little piece of stiff sharpened wire so that it would touch the crystal at a very small point (making the point junction, as galena is actually a semiconductor). This was a painstaking effort, and my dad helped a lot with ideas for how to make an adjustable mount, and especially with the testing. You test one of those things by running an old-fashioned electric buzzer nearby. Those buzzers produce large quantities of broadband radio noise, perfect for this purpose. To test the point junction, we'd start up the buzzer (which makes a very annoying audio noise that we muffled by putting it in a box) and listen in the headphones for noise, like a loud hiss. It probably took us two or three evenings to get a point junction we were satisfied with. Even the first one we tried worked, but the quality of the various attempts was wildly variable. After we did ten or fifteen of them, we had a good feel for what a “good” point junction sounded like, and we kept at it until we were sure we had the best one we could get.
Finally, after however long it was, I finished building the radio. It sat there in all its glory, a crudely constructed monstrosity of homemade parts, bits and pieces hanging about everywhere. To me, though, it was painfully beautiful. But would it work? To find that out, we needed an antenna. And one thing my dad knew well (and the book reinforced this): the longer the antenna, the better any crystal radio would work. This is because a crystal radio is unpowered and unamplified – the energy that makes sound in the headphones is captured directly in the antenna – and the longer the antenna was, the more energy it would capture.
The antenna was my dad's project – both because it really required an adult to clamber up to the roof, and way up a tree, to mount it – and because it was a potential danger, as it could guide lightning right into the house. My dad used some steel wire for the antenna, which ended up being (from memory) about 200' long. One end of it was attached to our house, right above my bedroom and the basement's casement window that led into his workshop (where my crystal radio would live). The other end of the antenna was on a huge beech tree to the south of our house, across the end of a little meadow. I remember my dad on the ladder on our house, but I don't remember how he got the other end so high up on the beech tree – but somehow, he did it. Then he carefully attached a “lightning arrester” to it before running it through an insulating sleeve into our basement.
After that, all that remained was to connect the radio to the antenna and to a ground wire (that was easy, as we had copper pipes right near by that ran underground). The evening after he got the antenna up, my dad helped me hook up the last few things, put the headphones over my ears, and we started playing with the radio. It worked! And on the very first try – something I know now is not the usual outcome on such a large project :)
Over the next couple of years, I spent quite a few hours down there in our basement, mostly in the evenings when reception was better, listening to many different things on that radio. I'd often call my dad over to help me understand something I was hearing, as so much of it was a complete mystery to me. One of those times, his face lit up as he listened – and he told me that I was hearing the sounds of radio teletype, which he had operated during the war. That was a sound he knew very well, and he could tell just by listening whether the operator was skilled or not (that has to do with the tempo of the operator's typing). I heard foreign languages, Soviet and Cuban propaganda (in English), the beeping of a satellite, interference from our tractor, and of course all the local AM stations. I also heard ham radio operators, and that triggered an interest that lasted for years – I was W2PKB, operating until the mid 70s.
Many years later, as my dad and I drove from San Diego to Lassen National Park, we had a long conversation about that crystal radio. He remembered it very well, but mostly for a reason I'd never have guessed at the time: helping me build that was a big challenge for him! His knowledge of electronics was very rudimentary, just the odd bit he'd picked up while operating radio teletypes during the war. The crystal radios he'd built as a kid used purchased condensers and attenuators, and pre-made cat's whiskers – making those was entirely new to him – and he wasn't at all sure his skills were up to it! Apparently there were quite a few times when I asked for help on something he had no clue how to do – he'd read the book and do his best to follow the directions. He also remembered testing my variable condensers after I went to bed, to make sure they didn't have any electrical shorts in them – those shorts would make them completely fail. The biggest surprise for me in that conversation, however, was when my dad asked if I remembered my Uncle Earle “inspecting” the crystal radio on one of his visits. I have no memory of that at all, but my dad told me that my uncle – an accomplished electrical engineer – was very impressed. From my dad's request for the headphones and galena crystal, he had no idea how sophisticated that crystal radio was going to be. For those readers who know some electronics: the crystal radio included an antenna tuner, a two-stage hi-Q “discriminator”, quite broadband coverage through three separate switchable, tapped tuning coils, and a two-stage (coarse/fine) variable condenser for tuning. My uncle offered to help my dad encourage me in getting interested in electronics – which, on a visit to his home a few years later, he did. But that's another story...
Writing this piece makes me want to go build another crystal radio :) But I know it just wouldn't be the same without my dad being there...
Sunday, November 24, 2013
Pater: the crystal radio...
Posted by Unknown at (permalink) 9:39 AM 4 comments:
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