Revox a77 dating

The circuit board in each of these cheap little walkie-talkies, for example, has just three transistors, a quartz crystal to ensure frequency stability and a handful of common components to transmit and receive voice messages over a distance of several hundred metres.Admittedly the range isn’t up to much, but wire-less two-way communications over any distance is actually a remarkable feat, especially when you consider that when new they cost just a few pounds, and were effectively just toys.Although this appears to be a very basic function, routing call and two-way audio traffic through a two-core cable is a surprisingly complicated business involving a fair amount of what we now call logic, yet it achieves this using just a couple of simple switches and some ingenious wiring.These days it would all be handled by a microcontroller, at the very least.Luckily the only damage was to the foam pad it sat on, and again this was easily replaced.I doubt very much that the current range sound quality is significantly different to what it was when new, and needless to say neither is going to win any prizes, but let’s not forget that it manages to send and receive intelligible voice communications using just a few cheap components.It was one of hundreds of walkie-talkie sets on the market in the early 60s.Most of them, like this one, operated on a small portion of the Short Wave band, around 27MHz, set aside for Citizen’s Band radio.

The current generation of inexpensive legal ‘consumer’ walkie talkies operate on multiple channels on UHF band, have many flashy features, like LCD displays, winky lights and a range of between 3 and 5km, but where’s the fun in that?

Unusually for a 60s vintage electronic device the electrolytic capacitors didn’t need replacing and the only maintenance needed was a few squirts of switch cleaner to get rid of pops and crackles from the PTT switch and volume control.

One of the aerials had lost its ball tip; I just happened to have a spare in my box of bits, and there had been a minor battery leak at some point.

This was, and still is a set of frequencies used for local two-way radio communications, that anyone could use, with minimal regulation or formalities or the need to have a transmitting licence.

They have just two controls, a volume, on/off thumbwheel, and a press-to-talk (PTT) switch on the side.

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