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Recently I have read about radioteletype devices capable of sending text messages via radio waves already in the first half of 20th century. Unfortunately, these teletypes used Baudot code, which is too limited for my needs. Ideally, I would like to have robust, wireless text transmission over large distances using at least 256-character encoding, including control signals (no transistors allowed, just vacuum tubes).

Initially I thought that devices should use QAM, since it allows to send multiple "bits" in one signal, but I fear 256-QAM would be too difficult for simple electronics of the era. Is it so? Would it be possible to build 256-QAM equipment in 1940s/1950s? If not, what other technology can I use?

I am specifically asking about the possibility of developing enhanced radioteletypes capable of being deployed in vehicles like trucks, ships of aircraft, not about some experimental equipment working only in lab conditions.

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  • $\begingroup$ This would require a reason for the focus on these kinds of scientific developments, but it would seem possible. $\endgroup$ – ThatCamal Dec 13 '18 at 18:25
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    $\begingroup$ Certainly it's possible. What do you think ASCII is? You could easily send ASCII with a telegraph key, though it'd be inefficient. $\endgroup$ – jamesqf Dec 13 '18 at 18:28
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    $\begingroup$ QAM is a method to transport a bitstream, Baudot a character encoding scheme. There are additional possible layers in between, e.g. error correction. What exactly are you after? All of it? :-D $\endgroup$ – Karl Dec 13 '18 at 18:30
  • $\begingroup$ @Karl Good point, thanks. I used a mental shortcut - what I want is a most plausible/efficient method of sending encoded characters wirelessly, with automatic encoding/decoding (rather than a human pressing telegraph key manually), with RTTY using Baudot code as an example of what I want, but I want it better (namely, more characters). I am just not sure if "better" was plausible for that era, and if RTTY was the best possible approach. $\endgroup$ – Ijon Dec 13 '18 at 19:01
  • $\begingroup$ Stupid question: How fast do you want this to work? If you want a higher type rate than what a professional typist can do, then you need data storage at least on the side of the sender. $\endgroup$ – Karl Dec 13 '18 at 19:56
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ENIAC was started up (in secret) in 1946 -- a programmable digital computer built entirely with vacuum tubes. It was an advance on previously existing electromechanical (relay-based) computing machines mainly in terms of speed, being around 100 times faster.

Those earlier relay-based digital computers, as much so as ENIAC, with limits on transmission rate, had the capability (had anyone seen the need to replace Baudot coded teletype) to handle a serial data stream, capable of transmitting any desired data (as it was, many years later, when computers began to communicate via modem on analog telephone lines).

To provide more available characters (as to handle multiple language text, arbitrary bitmap images, etc.), one merely needs to increase word length. Baudot was a 5-bit system; originally, ASCII was 7-bit, expanded to 8-bit around the time microcomputers appeared. The difference is protocol, not hardware technology -- if your transmission system can send one bit wide serial data, any arbitrary encoding length is just a matter of the protocol the machines at the sending and receiving end use.

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  • $\begingroup$ Today we have a clear distinction between software (protocols) and hardware, but I got the impression that it was not necessary the case back then $\endgroup$ – Ijon Dec 13 '18 at 19:15
  • $\begingroup$ @ljon you should read about the works of Alan Turing and Grace Hopper, they did a lot to separate hardware from software. $\endgroup$ – Renan Dec 13 '18 at 20:09
  • $\begingroup$ Also this answer is worthy of a bounty. $\endgroup$ – Renan Dec 13 '18 at 20:10
  • $\begingroup$ @Ijon Actually, the distinction is constantly blurred. There's hardware, progammable logic, microcode, firmware, drivers, operating systems, applications, and sandboxed applications. The clear distinctions are convienient for having distinctions, but the push for better/faster/cheaper blurs the lines regularly. $\endgroup$ – Cort Ammon - Reinstate Monica Dec 14 '18 at 5:02
  • $\begingroup$ When Spectre and Meltdown came out and brutally impacted Intel CPUs, there was an open question as to whether it would be possible to patch the CPU with a software update or not. In the end, the answer was no. $\endgroup$ – Cort Ammon - Reinstate Monica Dec 14 '18 at 5:03

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