User Programmable Standards Converter

[`FRANK.C]

I haven't had much time lately for this project but I have been keeping an eye out for an 819 line set so I could check that it can do 819 lines OK.
On Friday I took delivery of a Sony 9-90UM that had traveled from France. I hooked it up today to the converter. As I was just interested in seeing the video and not concerned with sound for now I used a System A modulator.
Photos below of the 819 line video. It is clear in the first photo that the TV could do with some attention.

The converter is set up as follows
No of lines 819
No of active lines 736
Front porch 0.5 uS
Line Sync 2.5 uS
Back porch 5 uS
No of broad pulses 1

I think it is incredible how good the frame lock is even though there is just one broad pulse.

Frank

[ppppenguin]

When this is complete it will be a worthy successor to the Aurora WC-01. The latter hasn't been available for a number of years. Although Frank is unlikely to attempt standards such as CBS sequential colour, Baird 240/25p should be possible. This was never feasible on the SCRF converters.

The flexibility of an FPGA makes it very easy to program arbitrary output timings though getting the interpolation and other matters right is less simple.

Is there sufficient FPGA capacity to do 405 NTSC? Needs some multipliers and other logic. I can supply VHDL for a PAL/NTSC coder which could be adapted easily for 405 NTSC. Obviously need to store and interpolate the chrominance as well as the luminance.

[peter scott]

Photos below of the 819 line video. It is clear in the first photo that the TV could do with some attention.

Hi Frank,

The 9-90 has very poor LF response on VHF.

   

It is much better on UHF but still far from perfect.

   

Peter

[ppppenguin]

The 9-90 doesn't give very good pictures at all. But it's a very useful little set. We use 3 at the Dulwich museum as confidence monitors for the RF distribution system. I have a couple of the CVM-90 monitor version which are invaluable for 405 experiments.

[`FRANK.C]

Hi Jeffrey
The resources aren't overly abundant see summary in the photo below and I haven't finished yet. So probably not enough to do colour.

Hi Peter.
Thanks for the photos. I didn't realise that they were that poor on VHF. You have saved me a lot of chasing a non-existent fault.

Frank

[Spot Wobble]

The 9-90UB has - if I remember correctly - has a 2.5 MHz bandwidth on its VHF tuner, but 3.5 MHz on its UHF tuner.

Therefore if you insert 405-line video via a UHF modulator (negative vision modulation, FM sound, etc), depressing the VHF and UHF selector buttons simultaneously on a 9-90UB, you IN THEORY get a 3.5 MHz bandwidth to display 405 (the quoted bandwidth for 405 being 3.0 MHz, I believe). At any rate, the 405-lines pictures appear to have better horizontal resolution via UHF than VHF on a 9-90UB.

Should you wish, you can also display 625-line pictures via a system A modulator (converter function bypassed) on a 9-90UB (both VHF and UHF selector buttons 'out'), but the 625 display is in theory now restricted to 2.5 MHz, but you can potentially 'enjoy' sound-on-vision (courtesy of the AM sound) for 625-lines!

Best wishes,

Francis

[`FRANK.C]

Hi Francis
I must try a 9-90UB on 405 UHF to see the difference.
The buttons on the 9-90UM work a little different to the 9-90UB. They operate independently of each other. Excerpt from the 9-90UM user manual below.
Sometime I may convert the 9-90UM for video input. The 9-90UB can be converted so I would expect the 9-90UM should be convertible as well.

Frank

[Spot Wobble]

Thanks Frank - out of interest, how difficult would it be to get a (correct) video OUT signal (from the VHF tuner) from a 9-90UB, please?

I understand that the French (and Belgian) 819-line system was positive vision modulation / AM sound when on VHF (like 405), but not sure if this was true when on UHF too?

Best wishes,

Francis

[ppppenguin]

I don't think that 819 was ever transmitted on UHF.

The Belgian version of 819 (System F) was a nasty kludge with heavily reduced vision bandwidth.

[Murphyv310]

Hi.
If you modulate 405 onto a UHF modulator and depress the buttons on the 9 90 the resultant 405 line picture is good.
The 9-90 on VHF has poor LF response but is still capable of around 2.7mhz bandwidth. The issue on VHF can be put right as its down to mostly electrolytic caps but the job is very fiddly.
On UHF they will resolve 5mhz. So when hit with 405 on UHF and you just switch the time base resolution is very good indeed.