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!
After finding the dead LCD screen that was to be a 5.6GHz ATV receiver it also turned out that the 7″ Pi screen on my Portsdown setup had similarly died – just white lines on the screen. No amount of stripping, reassembling and general fiddling fixed it. A new screen did.
Anyway, I now have a Winterhill receiver. This came from a fellow ham and saved me building one. As is usual with any new box one absolutely must try it right away, which is how I discovered the bust screen on the Portsdown. After that was replaced I successfully sent a test card 40 inches across the desk! Small steps… and at least the Winterhill is in a nice box unlike my Portsdown which is still waiting for a suitably sized case – why is it all the nice metal boxes are a few mm lower than the 7″ display needs. Huh.
I had a quick fiddle with the box of bits that should by now – in fact by a year ago – be a 5.6Ghz ATV transceiver. I now have a couple of Gibeon flat panel antennas which claim 24dBi as mentioned in the excellent resource on this topic at http://5-6ghz-atv.co.uk/
So, let’s have a play. I got a rather old fashioned Sandisk Photo Album, a slab of plastic that takes 5V and will present photos (and videos and sound files) to a TV via an AV output and the typical red, white and yellow RCA plugs. First off I needed to make sure this worked. So, what has an AV input… er… Bedroom TV? Nope. An older Sony TV in another bedroom does and so it was plugged up. And nothing. Problem 1, it seems to take an age to turn on in response to its remote control. No switch of course. Problem 2, it would not read anything on the SD card I had with a test card image on.
The only clue is it needs a ‘JPEG (Baseline, up to 16 Megapixel)’. No idea what I had produced via GIMP on the Linux box but it would not find anything at all. Maybe it’s the SD card. I found a very old 32Mb (!) SD card with some sundry photos on and those were fine. Ah, so maybe it cannot read big SD cards. Copied the test card file onto that and now it at least finds the card but says the format is unknown. After 3 iterations I fed the jpeg into Windows Paint, saved it (as jpeg) and it worked.
And success, I can send the test card image to the TV via the TS832 transmitter and RC832 receiver. Next, I tried the flat panel antennas and they worked too, not that I would have expected any less as the little rubber duck antennas worked fine.
However, offering the AV to my 12V monitor (ex eBay car reversing screen) just showed lines. No amount of shouting fixed this and it would appear that this monitor has simply died, perhaps having got fed up waiting in a box all this time.
Anyway, now I need to actually construct the thing properly and work out a mount for the antennas.
Since I built the Minitiouner I’ve had nothing to test it with except a quick test on the Astra satellite to prove it actually worked. Not any more. I now have a Portsdown ATV transmitter setup thanks to a recent advert for one for sale (saved me having to get all the bits). No PA, no antennas or anything else here yet, but I did at least manage to send a test card from it to the Minitiouner over 23cm and at the grand distance of 6 inches.
It all needs a nice case yet but it’s a good start. This might even persuade me to bung my 23cm yagi on the chimney and see if I can actually receive GB3YT – it’s not too far away but there is a house in the way.