80 column 80 column & UAV composite

[+hloberg]

80 column text on the Atari 8bit, with out using the XEP80 or some modified video card, is created by using GRAPHICS 8 and a 4 character wide font. It works fairly well on an unmodified Atari IF you have a a B&W TV or, even better, a monochrome monitor. A color TV, LED TV/monitor or even some composite monitors, no so good (See 1st picture).

The screen is created by a BASIC program from ANTIC called Easy80 (attached). As you can see the font is only sorta readable on my color LCD monitor.

 

But, while installing my new UAV chip in my 600XL I once forgot to hook up the color line and the video was just B&W. This got me thinking. What would the screen look like if I disconnected that line and then ran the Easy80. (picture below).

 

 

That is really clear. Here is a picture in the XL of the line I disconnected.

 

The line is supposed to be connected to the screw connector at the top to supply the color.

 

IDEA! put a switch on the back of the computer to turn off that line on when I want sharp B&W or 80 column.

Before I do it is there any reason I shouldn't do that? Is there something I'm missing that might hurt or damage my XL when the switch is off. what ya'll think?

 

disclaimer: I have my UAV set up for composite only. If you have setup for S-Video with separate chroma , should work the same but haven't tested it. 

easy80basic.atr

Edited April 26, 2021 by hloberg

[+DrVenkman]

Congrats - you've just discovered LUMA-only video.   

 

Yeah, if you have an S-video monitor with separate Chroma/Luma, you get sharp Gr.8 80-column text without the need to disable the Chroma output. Composite video is called "composite" because it's a combination of the two signals into one; your switch to disable the Chroma part of the composite signal effectively turns your "Composite" output into LUMA-only. I have an old Apple Color Composite Monitor from the mid-80's that has a switch to kill the Chroma part of the input and do the same basic thing on the receiving end of the signal rather than the sending end as you have done. 

[+hloberg]

54 minutes ago, DrVenkman said:

Congrats - you've just discovered LUMA-only video.   

 

Yeah, if you have an S-video monitor with separate Chroma/Luma, you get sharp Gr.8 80-column text without the need to disable the Chroma output. Composite video is called "composite" because it's a combination of the two signals into one; your switch to disable the Chroma part of the composite signal effectively turns your "Composite" output into LUMA-only. I have an old Apple Color Composite Monitor from the mid-80's that has a switch to kill the Chroma part of the input and do the same basic thing on the receiving end of the signal rather than the sending end as you have done. 

I had thought about going the s-video route when setting up the UAV but with less and less new TVs supporting S-video, and my one and only s-video tv getting really old, I thought, what's the point.

I'm concerned I might introduce some interference with the switch so a test setup is only way to find out.

[_The Doctor__]

S Video is not only cleaner and clearer but normally shows more lines, which helps with some software.

[Dinadan67]

6 hours ago, hloberg said:

IDEA! put a switch on the back of the computer to turn off that line on when I want sharp B&W or 80 column.

Before I do it is there any reason I shouldn't do that? Is there something I'm missing that might hurt or damage my XL when the switch is off. what ya'll think?

Even if your monitor/TV does not have a S-Video input here is no need to modify the machine. You can just solder a cable that connects only the luma line to composite. I did that back in the day to get the best possible picture out of a monochrome (amber) monitor.

[+hloberg]

here is more software for the Easy80. It includes a version for TurboBASIC XL, some docs, a terminal program & other stuff.

easy80.zip

[+hloberg]

8 hours ago, Dinadan67 said:

Even if your monitor/TV does not have a S-Video input here is no need to modify the machine. You can just solder a cable that connects only the luma line to composite. I did that back in the day to get the best possible picture out of a monochrome (amber) monitor.

 

So, on an unmodified 800XL you could create a cable with pin 2 (ground), pin 3 (sound) and then tie pin 1 (composite) & pin 4 (luma) together and get a sharp B/W luma only picture? OR would just using only the luma line to composite enough?

 

& US 600XL has only RF is why the UAV & composite setup & the need for a switch.

Edited April 26, 2021 by hloberg

[+DrVenkman]

8 minutes ago, hloberg said:

So, on an unmodified 800XL you could create a cable with pin 2 (ground), pin 3 (sound) and then tie pin 1 (composite) & pin 4 (luma) together and get a sharp B/W luma only picture? OR would just using only the luma line to composite enough?

If you only want a sharp monochrome image, use only the LUMA signal from the 800XL.

[+hloberg]

here is the finished product. switch down color, up sharp b/w.

Edited April 26, 2021 by hloberg