
You Could Download Video Games from the Radio in the 1980s - bpierre
https://interestingengineering.com/you-could-download-video-games-from-the-radio-in-the-1980s
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jhallenworld
The article mentions modulation techniques but doesn't really explain the one
actually used by these classic computers: pretty much they all used FSK-
frequency shift keying. One tone is a 1 and another tone is a 0.

The playback usually has a limiter such that the software gets no amplitude
information. It really just gets zero-crossings, and has to time successive
crossings to determine the frequency.

The cassette recorders used for this were basically the cheapest, lowest
fidelity ones. Their frequency response was around 200 - 8000 Hz. Even so,
this was good enough for 1200 - 2400 Baud FSK. It's interesting to consider
what data rate you could get from these tape recorders using the best possible
techniques available in the 90s- QAM from modems, or even OFDM used in Telebit
Trailblazer modems (now used in LTE cell phones). Of course the problem is
that the modem would have more CPU power than the home computer itself..

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hoyd
I Northen Norway, in the 80s or 90s, at least when Commodore 64 was popular,
teachers would distribute IT/Engineering exam/test exercises over the
universities local radio, for students to record on cassettes and then replay
on their C64s. When I was told this many years later, and each time I reflect
on it, it sounds to cool.

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unicornporn
This method was mentioned in the piece about the Galaksija[1] that made it the
first page of HN last week or so.

[1] [https://tribunemag.co.uk/2020/07/make-your-own-self-
managed-...](https://tribunemag.co.uk/2020/07/make-your-own-self-managed-
socialist-microcomputer)

