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Many classic computers could optionally use a TV set as the display. At least in the early (pre-SCART) days, the TV would typically only have RF input, but if you were using a monitor, you could get a better color picture, not just because of the quality of the picture tube itself, but because you could use a better transmission format. Composite video would save an RF encoding step, but best of all was when computer and monitor could connect with an RGB cable, avoiding the distortion that comes with mixing the components together and separating them again.

Did some of this apply even with a monochrome system? That is, if you had a monochrome computer providing RF output to a black-and-white TV, and you wanted to instead connect it to a green-screen monitor, could the monitor produce a sharper image if it gets the signal in a different format than the TV could take?

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RF encoding introduces significant noise to the video signal because it moves the signal up to an area of the spectrum that is much more susceptible to interference. A monochrome 240p video signal of the best quality will be defined by its dot clock frequency at ~14 MHz. This would create a good quality 80 column text image as seen on machines like IBM CGA or Amiga. For RF compatibility, such a signal would be promoted to the TV VHF spectrum, which resides in a large and noisy range of ~50 MHz to ~250 MHz. Here, the signal is subject to interference from the many other signals present in the VHF spectrum. Thus, even without any distortion from the frequency shift (not possible), the quality of the signal as is transmitted to the TV is significantly degraded by noisy spectrum interference. Naturally, the TV also has to shift the signal back down to the native frequency as well, and this too is imprecise.

So you have noisy artifacts introduced through both the up and down frequency conversion needed for RF transmissions to the TV, and you have the fact that you are moving the signal into a much noisier spectrum band where it is interfered by other signals.

Therefore, yes, any avoidance of RF encoding, even for a basic text-only monochrome display, will benefit the display quality. Examples of bypassing RF encoding to achieve better results using a monitor are readily seen amongst various early computers, including the 1977 Apple ][, Commodore PET, and TRS-80 Model 1, all of which relied on bypassing RF for more readable text displays on monitors.

In my opinion, TV sets as computer monitors was never meant as a practical alternative to a monitor if you were utilizing anything other than low-resolution color output, probably for games. The fact that early computers supported RF was more for keeping the costs/barriers to entry lower for the target home market, since virtually all homes already had one or more TV sets. It's the same reality that has always applied to home game consoles, where the output capabilities improved almost lock-step with the capabilities of low-cost consumer display devices (e.g. "TV's") to the present day.

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    I suspect the biggest problem with RF encoding is the 6MHz channel bandwidth (8MHz for PAL/SECAM) rather than the noise. – Ken Gober Jan 4 at 13:48
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    @KenGober You are right that there are multiple factors and I've expanded the answer. – Brian H Jan 4 at 13:51
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    Would good cabling minimize the interference? – Thorbjørn Ravn Andersen Jan 4 at 14:04
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    @ThorbjørnRavnAndersen I know from experience that using thick coaxial cable and barrel connectors works better than cheap antenna wire. But still no substitute for connecting to a monitor/non-RF input. – Brian H Jan 4 at 14:06
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    Then there's the fact that the RGB signals are square waves. However, note the converse as well. Historically, people made use of the properties of colour composite video in ways that did not work with RGB monitors and needed colour composite TVs, although this is well beyond what the question is asking about, which is B&W composite video. – JdeBP Jan 5 at 17:17
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Not answering answering your question, but "black and white" TVs did produce a "better" picture as they didn't have the wire mask behind the glass, which was often very coarse on early TVs and even monitors. You could sometimes/often get a better grey image on a B&W TV than colour on a monitor.

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    Also, many cheap black and white TVs wouldn't try to remove the colour subcarrier, so wouldn't end up softening a genuine black and white signal. – Tommy Jan 10 at 16:24

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