The early limits on television picture quality

[peter scott]

A pretty definitive answer to my principal original question there.  Thanks.  Also in agreement with Peter's advice.

So, there were an awful lot of caesium 'nodules'. Another example of impressive 1930s technology.

Steve

The impressive technology was actually accidental! look for the name of Sanford Essig here.

Peter

[Panrock]

What a splendid and authoritative web site you have there Peter!

Something really basic I should understand about the Emitron but don't. What about the trapezoidal scan distortion on the scanning raster, in the vertical sense, resulting from the gun being at an angle to the mosaic plate? And the possible beam focus changes too? What was done about this?

Steve

[ppppenguin]

Section 2.2 of the Black Book is about the Keystone Generator. This compensates for the trapezoidal distortion of the raster by mixing appropriate amounts of H and V scan waveforms before they are amplified to feed the scan coils. Section 4.1 is about the Focus Panel. In a quick skim I didn't see anything about dynamic focus.

[Panrock]

Thanks for clearing that up.

Steve

[Kalee20]

Wouldn't it be more modulation of the H amplitude by the V scan?

At the top of the mosaic (bottom of the picture, owing to the inversion caused by the camera lens), the same deflection in degrees will cause a greater linear distance across the mosaic than it would at the bottom of the mosaic. So the line scan needs to be smaller amplitude here, than it does at the bottom of the mosaic (top of picture).

That, to me, says modulation, not mixing...

[Panrock]

Cue discussion of the difference between modulation and mixing. Without checking first, is mixing where each component waveform modulates the other?

[ppppenguin]

I think it is technically modulation. The Black Book is available freely online from more than one place. So you can follow up the details if you wish. The scan that the late Brian Cuff and I did is a big file (325MB as a zip), too big for the GVR archive.

[Murphyv310]

Is there a link to the scan Jeffrey?

[ppppenguin]

I think we discussed online versions of the Black Book not too long ago here on GVR. Here is one version: http://www.earlytelevision.org/ap_black_book.html Not sure whose scans but that doesn't matter. Could be Brian Cuff's could be Simon Vaughan's (APTS).

[peter scott]

Is there a link to the scan Jeffrey?

If you hit here then the titles relate the appropriate section of the Black Book to the diagram above.

Peter