Tag: datv

QO100 DATV reception finally

Well, that made quite a difference! I removed the POTY from the QO100 dish today and replaced it with a ‘Bullseye 10kHz’ LNB sourced from Amazon and advertised as a ‘QO-100 Bullseye TCXO LNB’. It’s just clamped in place with no attention to position or skew. Winterhill plugged in and instantly I see pictures.

The LNB behind the POTY only managed negative values in the MER and D fields, this one seems too work rather well. No idea what happened to the old LNB but these things happen I guess. It’s dry and had a waterproof housing. I’ve used the existing CT125 cable and connectors. Now to put the Winterhill box in a better location than just sitting on a ladder tied on with a bit of wire!!

The above photo shows the Winterhill viewer and console on the left and the Quick Tune on the right, all working nicely.

QO100 DATV attempt

Well this got off to a bad start! Ahead of my plan to move the QO100 disk so I can get the electronics in the loft rather than the garage I wanted to test out the Winterhill box to see if I could pick up any DATV on the wideband transponder.

The Winterhill box generates the 18V necessary for the LNB so in theory it was just a matter of pulling the coax feed from the bias-tee in the garage and putting that into the Winterhill. That done, I could see the occasional signal but never a picture.

Now, I had noticed that the NB beacon strength had dropped a while ago so today I decided to adjust the dish in case it had been knocked. That snowballed! I needed a laptop so I could see the signal strength while at the dish (remember the dish is on the garage wall currently at about 6 foot, so easy reach). Of my two laptops one is a Mac and had no SDR software, the other a Samsung Netbook running Ubuntu and terribly slow. I tried setting up several SDR packages on the Netbook and failed miserably. At this stage I need to state that after a lifetime working in IT and solving problems I now have no time or patience to solve my own, so if something fails it goes to the bin!

So, the Mac. CubicSDR refused to even think about installing. I found SdrDX which works with the USB Funcube dongle amongst other, mainly networked things. This worked just fine.

Mac out on a lab stool in the shade, SdrDX and the Funcube running, the bias-tee in the garage powered up, a cable fed out the garage back to the dish and into the Funcube… fortunately it didn’t all fall over and actually worked. So I adjusted the dish but only gained a couple of dBm more than before no matter what I tried. Oh well…

Back inside and plug the Winterhill in. Back upstairs to the Windows PC and now I see locked signals but just not enough signal strength for a picture.

I wonder if the LNB is full of spiders…

Anyway, now the QO100 kit in the garage is in bits I can’t transmit so it can all stay as it is. My next plan is to remove the POTY and install an LNB and see if that gets me any DATV pictures, otherwise I am a bit stuck. The 1.2M offset dish has a clear view of the sky and should be ideal – it worked just fine for SSB on the NB transponder. I never got round to sorting out a GPSDO input for the Pluto but I am about to get a SG Labs 3cm transverter and plan to use an actual transceiver for tx once the dish is moved.

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!

Portsdown progress

It really is taking me far too long to get this sorted out. But, finally some progress has been made… at least I now have a decent case and the screen mounted. So far, there is very little else in the case other than the Lime and Pluto, the screen, the Pi and a 12V to 5V converter. But at least there’s plenty of space to add all the other necessary bits and pieces.

The screen was the most awkward thing to mount as it is designed to fit easily into a plastic surround with the Pi directly behind. For that, the 4 mounting screws fit directly to the case. But here I want it in the front panel. My rather less than elegant solution was to get some 1/4″ square aluminium bar, make holes for 4 M3 nuts and bolts and tighten these to become studs – these are in the horizontal pieces as shown in the pic. These were then epoxy glued to the front panel. Two more bars then take the screen, with spacers so the screen isn’t pulled back too much when tightening.

Anyway, elegant or not you can’t see it from the front! Still to go on yet are the three push buttons and encoder / tuning wheel for the Langstone transceiver part of the kit. As for the rest, well, one thing at a time! But anyway it works… as shown by yet another successful 6″ transmission to the Winterhill box sat on top!

More ATV fiddling

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.

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