Video signal to TV with only "External Antenna" Jack?

[treehouse391]

Hi all;

I'm a little new to vintage televisions, but would like to know what options might exist to feed an early transistor TV (1970s) with a video signal, if it only has an "external antenna" jack.

In trying to recreate a period-specific display, I need one of these older TVs to be displaying video coming from a computer. I have an older computer that can give me a composite signal from its graphics card (RCA jack), but how do I get that onto the older TV? What can I feed to the external antenna jack?

Many thanks,
Tim