Testcards

I've been meaning to set up something to generate a testcard via composite video for a while and, as is typical of me the ideal solution was sitting there in a BATC magazine on my bookshelf. CQ-TV No 270 has the details of one such setup using a Raspberry Pi Zero. I don't have one of those and Pi systems are hard to come by these days but surprisingly I had a 3B not doing anything. Software downloaded, 4-way jack to RCA plugged in and connected to a TV and, nothing. Well, a buzz. Checked the cable, all ok. Checked what the Pi wants...

...why does the Pi have to have the connections different from what appears to be a standard hi-fi 4-way to RCA lead? Or, rather, why does the hi-fi 4-way lead I have have to have different connections? Grumble.

Ok. I wanted to test this seeing I had it all sitting in one of the bedrooms attached to a TV. Stripping down a 4-way jack lead that I never needed and which was far too short to be of use I made a lead. It would last probably half a second in normal use but worked sufficiently well to prove the setup.

It is of course a waste of a 'whole' 3B, but until I get a Zero this at least lets me push a testcard out when I need one. The alternative has been to use the rather clunky Sandisk device that can present an SD card or other media to an a/v output, as used in my first 5.6GHz setup https://m0rvb.uk/index.php/2021/05/22/5-6ghz-experiments/ - this way is a whole lot neater!