Using "Z" Mod on a scope.

[Murphyv310]

Here we go:
180/25p.

[Mike Watterson]

The linearity issue is not the 555 frame generator but the scope switched to AC coupling.
Perfect linearity on DC coupling.

Ooops. Looks very linear now

Now an Amber/Blue scope CRT and no graticule

[`FRANK.C]

Excellent result Trevor.
I haven't seen 180 lines before, it contains more detail than I would have imagined.

Frank

[Terry]

If you think about it, Frank, 180 lines* it isn't much different from a 405/50 display with poor interlace!

The real difference, obviously not visible in Trevor's stills, would be the presence or relative absence of flicker when comparing the two systems.

Trevor, congratulations on your efforts!

* Trevor, as our multi-standard expert in this thread, how many of the 180 lines are active compared with one 202½ line field of a 405/50 signal?

[`FRANK.C]

Hi Terry
That's a good point, I've see 405 with no interlace which I guess would be close.

Frank

[ppppenguin]

If you think about it, Frank, 180 lines* it isn't much different from a 405/50 display with poor interlace!

There's an even more important point. Interlace only gives you a boost to vertical resolution for stationary pictures. As soon as thing start moving at any significant speed the resolution drops to the number of lines in each field. So for moving pictures the Baird 240 line system had better vertical resolution than the M-EMI 405 line system.

The Baird system had another advantage. 240/25p needed about half the bandwidth of 405/50i to give the same horizontal resolution. With early cameras etc struggling to get 3MHz BW this was a real benefit. Of course the 405 system had more space for improved kit to give better pictures. What we now call "future proofing".

[Murphyv310]

Hi.
The German 180/25p line system has 169 active lines.
The full specs are here: https://en.wikipedia.org/wiki/180-line_t...ion_system

Next thing to do is to construct a larger screened monitor and something not using a green display. Would like to stick with an electrostatic tube about 5-6 inch, any suggestions?

[ppppenguin]

Might it be worth hacking an ordinary TV? Winding down the line scan frequency might not be too much of a problem but you'd almost certainly need a separate EHT supply.

[Geordie McBoyne]

In Germany the 180 line system was replaced in 1938 by a 441 line 50Hz interlaced system. In terms of active lines the system had no practical advantages over our 405 line standard.   58 lines were blacked out during the frame sync period compared with only 28 lines in our 405 line standard. Because of the higher line frequency the video bandwidth should be about 3.0Mhz and was in fact only 2Mhz whereas 405 was engineered for 2,7Mhz. The French version of the 441 system had a wider video bandwidth to accomodate the 4 : 3 aspect ratio.
441/50 German standard, I believe the aspect ratio was 1 : 1. Early 405 was 5 : 4, later 4 : 3.
So all in all it was an inferior system compared with our 405 line system.

Read about 441 line television here:  https://en.wikipedia.org/wiki/441-line_t...ion_system

Geordie McBoyne.

[Murphyv310]

Thanks David.
On 180 lines we have 169 active lines and on 405 we have 377 active lines, consider an interlace fault or moving scenes and on 405 we are down to 188.5 not really a kick in the shirt away from 180 lines. The downside of course is the constantly annoying flicker, no matter how good these systems could have been the flicker takes away any enjoyment from viewing program material and no doubt leave you with a thumping headache!!!