Electronic – “rabbit ear” in a video-capture context

It used to be possible to get these little modulator units that took NTSC video in, and would put out a signal on channel 3 or 4. Not sure if you can still get those, they were common in early 80's 8-bit micros, back when nobody could afford actual monitors, and would let your computer drive a TV. With the demise of analog broadcasting, they probably aren't manufactured anymore, but you might liberate one from a defunct VHS machine. Curiously, a quick search reveals all manner of consumer productized ones available, which might work for you, too. The things I'm talking about look like so:

Anyway, one of those modulators, an NTSC camera module, and perhaps a bit of amplification (about 72MHz ?) and you'd have your own low power analog TV transmitter. And by low power, I mean RF, not battery draw. You'd probably get plenty of range on 0.1W to 0.5W of RF output. This might not even incur the wrath of the FCC until they get around to re-assigning the former analog TV channels.

This is why VGA displays didn't happen until long after the Z80.

Block graphics with sprites, or 1 bit per pixel monochrome graphics, or character ROM based display modes were the order of the day. Sometimes you could switch modes between them.

Using character ROMs, the ASCII character code provided most of the address into ROM, with (scan line mod 10) providing 4 LSBs of address. So you stored ASCII character codes into a small (maybe 2kbyte) RAM, and the video controller hardware read a string of 80 from this RAM, (10 times in succession for 10 successive scan lines) to deliver 80 bytes (640 bits) per line.

Those 80 bytes may come from a 128 byte section of the 2K RAM, to simplify the video addressing. Likewise the 10 scan lines come from a 16 byte section of the character ROM to simplify addressing. With a suitable design you can select a different page of character ROM with 14 or 16 bytes per character for a prettier font (and fewer lines of text on screen!) with only minor changes to the video hardware.

The 6845 video controller was a popular device that could handle this sort of addressing and simple bitmapped graphics; it should still be easy to find a lot of information on it.