NBTV Quickie

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NBTV Quickie

Postby Panrock » Mon Mar 05, 2018 4:40 am

The Convention draws nearer... and a natural gap opens up in my 405-line transmitter doings while I await the delivery of some important parts. So what better than to do a little "NBTV" for a change?

Pictured is my old colour monitor. Rather grandly originally called the "Grosvenor", this has since been mercilessly butchered. As has its companion mechanical colour camera (even bigger and harder to lift!).

Anyway, I thought it might be nice to get this old warhorse going again. This time, I am going to try adding the magnifier from my Argus, to obtain a really big 30-line colour picture. I will also look into converting it to horizontal scanning rather than vertical, with a higher (16 fps) frame rate. This would involve a lot more butchering, but why not? Life should be enjoyed.... :lol:

Steve O
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Re: NBTV Quickie

Postby Harry Dalek » Mon Mar 05, 2018 7:45 pm

Hi Steve
It was the first colour mechanical monitor i recall seeing on the net,have you scavenged parts since ?
I will keep an eye out what you come up with converting it .
So many ways you can go converting your monitor ,i am stuck on the electronic scanning side of the hobby at the moment so i will get my mechanical fix watching your conversion !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Quickie

Postby Steve Anderson » Tue Mar 06, 2018 3:02 pm

Good luck with this Steve. I think all the gubbins we put together all those years ago should quite easily handle the slightly increased bandwidth of 16fps, probably quite a bit more.

But if you run into trouble you know where to look...

Steve A.
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Re: NBTV Quickie

Postby Panrock » Tue Mar 06, 2018 7:38 pm

Thanks for the thumbs up chaps. Yes, and this rig has rectangular holes, with Steve A's PWM drivers and aperture correction too.

I have now started on some fairly major hacking about... first changing the motor cooling fan position to make room for the luxeon box above.

The disc natively gives an almost square picture, which is what the colour camera originally provided. l am changing from vertical to horizontal scan. I see there are two 30-line 4:3 horizontal scan standards to choose from on the WC-01 converter. So no more need for the water-filled cylindrical lens to convert to 'Baird' 3:7 (on vertical). With a 6-inch viewing lens, I am hoping for a 'giant' colour picture (by NBTV standards!}.

Photos will follow.

Steve O
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Re: NBTV Quickie

Postby Harry Dalek » Tue Mar 06, 2018 8:31 pm

Steve in case the lens idea is a bit dim blowing the image up ,i am not sure how much light you have or need ..
An idea on my to do list one day is a 2 disk line slit system like the 2 drum monitor some time back would give you the large image with a lot less light needed also give you a partly multi system adjusting your motor speeds ..2 slit disks back to back 2 motors .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Quickie

Postby Panrock » Tue Mar 06, 2018 9:43 pm

Hi Harry,

This is a 12-luxeon display with quite large disc and holes so is actually plenty bright. Also, the 'viewing tunnel' effect that comes with the lens carrier subjectively increases contrast.

I don't think a two-slit scanner would necessarily be more efficient than an equivalent Nipkow disc. But if such a system could be made using two traveling 'bands' (say), it should certainly be possible to obtain a big picture without magnification.

Steve O
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Re: NBTV Quickie

Postby Harry Dalek » Tue Mar 06, 2018 11:06 pm

That's good then Steve not to much mucking around having enough light you have won the battle .
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Quickie

Postby Panrock » Fri Mar 09, 2018 8:39 am

Some progress... looks better from the front I think! The rig has been converted from vertical to horizontal scan, and so I can now take advantage of the 4:3 aspect ratio and 16Hz provided by the WC-01. I can confirm the 16Hz frame rate looks much better than the 12½Hz. This is partly due to the brilliance of the display (when viewed in subdued light) emphasises the flicker. This is a Nipkow display that can be viewed in daylight if necessary.

I tried mounting the 6-inch viewing lens. It didn't actually provide a lot of magnification and was very heavy to mount and couldn't be centred. So, as you can see, I made a new visor. This is the rectangle at the top. It uses a Fresnel lens as a magnifier.

There's sound also of course and the results are very watchable for 30-lines. The contrast is high and the colours vibrant... has anybody ever made a 'saturation' control for RGB? It's best not to advance the aperture correction too far, though applying a little is highly beneficial. The range of adjustment of its time constant originally provided by Steve A seems OK at 16Hz.

I'll next try to take some off-screen piccies...

Steve O
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Re: NBTV Quickie

Postby Steve Anderson » Fri Mar 09, 2018 1:12 pm

Panrock wrote:... has anybody ever made a 'saturation' control for RGB? Steve O

Somewhere in the dim and distant past I did post a conceptual saturation control for RGB on this forum. I've looked through my folders and I can't find it. Its biggest drawback was it required a triple-ganged pot which are made of Unobtainium.

It could be done with three VCAs or three digital pots, but is it worth the hassle? An equal hassle would be RGB-YUV, only a dual-gang pot would be needed on the colour difference channels, then YUV-RGB.

Steve A.
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Re: NBTV Quickie

Postby Panrock » Sun Mar 11, 2018 2:13 am

Here are some off-screen pics. The blue rectangles at top-left are the 'pause' signs from the DVD player. The aspect ratio is still not quite right, so they are slightly vertically elongated. The noise is a camera artifact. Some overshoot from the Aperture Corrector can be seen on the piano shot.

The Grosvenor seems happy running all day at 12½ fps, but not 16. At 16 fps, after about a quarter of an hour, some rumbling can be heard! If I turn down the video levels, the flicker isn't so bad, so it'll be 12½ Hz from now on...

Steve O
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Re: NBTV Quickie

Postby Steve Anderson » Sun Mar 11, 2018 12:48 pm

Even with the overshoot the results are impressive! And all done in a few days. Well done Steve.

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Re: NBTV Quickie

Postby Harry Dalek » Sun Mar 11, 2018 2:53 pm

Yes very well done Steve, is that image amplified as well ? Talk about a Quicky ! :o
Great work . :arrow:
BTW the case must of been a hard construct when you made it ...
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: NBTV Quickie

Postby Panrock » Mon Mar 12, 2018 12:18 am

You're very kind, fellas. It's been put away, ready for the Convention now.

Thinking more about the saturation, I guess this must be determined by the colorimetry of the LEDs; ie. the narrowness or lack of overlap of their spectral characteristics (??) Personally, I like the vivid colours.

Steve O
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Re: NBTV Quickie

Postby Steve Anderson » Mon Mar 12, 2018 1:48 pm

Remember when colour TVs started to be bought, Mr Average would turn up the colour/saturation control to maximum, "I bought a colour TV so I'm going to have colour - and lots of it!" Newsreaders faces were bright red, caucasian skin took on an orange hue and trees had a flourescent green glow.

In the run-up to the official launch of colour TV in Australia people were able to buy colour TVs but the programs were still in monochrome, the TV station simply switched off the colour burst. Then some bright spark suggested. "Why don't we turn on the burst only during commercials?" Now everyone wanted to watch commercials! Sneaky!

Long articles appeared in Electronics Australia about how to recover the burst when it was suppressed, whether any of these worked I somehow doubt. But it was short-lived, just months later it was colour all the time.

Steve A.
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Re: NBTV Quickie

Postby Harry Dalek » Tue Mar 13, 2018 4:27 pm

Steve Anderson wrote:Remember when colour TVs started to be bought, Mr Average would turn up the colour/saturation control to maximum, "I bought a colour TV so I'm going to have colour - and lots of it!" Newsreaders faces were bright red, caucasian skin took on an orange hue and trees had a flourescent green glow.
Steve A.


Well Steve there's one thing Mr or Mrs average could not stuff up with the colour control ! :lol:
Its a wonder really why they have these controls for every one to adjust you would think it would be set and if you wanted to adjust the colour you have to know your stuff and adjust a trimmer in side the set ...that would keep wandering fingers out wanting bright colour's !
I recall seeing my first colour tv via next doors lounge room window which was across from my bed room window watching Gomer Pyle when we had the same show on in our lounge room i had it made at 14 sound as well :wink:
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