Young electronics hackers today are very fortunate to grow up in an era with both a plethora of capable devices to stimulate their imagination, and cheap and ready access to them. Less than the price of a hamburger meal can secure you a Linux computing platform such as the Raspberry Pi Zero, and a huge choice of sensors and peripherals are only an overnight postage envelope away.
Casing back a few decades to the 1980s, things were a little different for electronically inclined youth. We had the first generation of 8-bit microcomputers but they were expensive, and unless you had well-heeled parents prepared to buy you a top-end model they could be challenging to interface to. Other electronic parts were far more expensive, and mail order could take weeks to deliver the goods.
For some of us, this was not a problem. We simply cast around for other sources of parts, and one of the most convenient was the scrap CRT TV you’d find in nearly every dumpster in those days before electronic recycling. If you could make it from 1970s-era consumer-grade discrete components, we probably did so having carefully pored over a heap of large PCBs to seek out the right component values. Good training, you certainly end up knowing resistor colour codes by sight that way.
In the Age of Analog Broadcasts
A personal fascination of mine as a young radio amateur was with the analog tuner you’d find in these sets. This was the RF front end that converted the signal from the antenna into a 36MHz intermediate frequency for the set to demodulate and display. These tuners were simple enough devices usually having only a couple of transistors, an RF amplifier and either an oscillator and diode mixer or a combined mixer/oscillator.
Where I grew up in the UK they were all for the UHF TV bands (about 470 to 860 MHz), and they were either mechanically tuned with variable capacitors and cavity resonators or electronically tuned with varicap diodes and stripline resonators on a PCB. They were discrete modules inside the set, usually in a screening can about the size of a pack of playing cards. Their stand-alone nature meant that once removed from the set they offered considerable potential for modification and repurposing to other UHF uses, and an accessible way to learn the ropes of UHF construction.
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