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See TV in a CRT monitor without using CPU !! - RF Cafe Forums

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Below are all of the forum threads, including all the responses to the original posts.


Koroth
Post subject: See TV in a CRT monitor without using CPU !! Posted: Sun Feb 19, 2006 12:35 pm

Lieutenant

Joined: Sun Feb 19, 2006 12:26 pm
Posts: 1
Actually this is related to a more complex project(like what i done in the Van eck phreaking project). Please help to solve my problem. I am going to present it in a nice way. You may think this as weird. Please dont give a complete alternate suggestion. Yes this is weird.

Basically I am going to use my old CRT monitor as a CRT tube only. The rest of TV circuits are going to be added to it.(Like tuner, demodulation etc..). Ok now scenario clear .....

After the received signal from the antenna I will tune it amplify it and demodulate it to get the video data.

Now I have the monitor ON with power supplied to it. The Data input to the monitor(15 pin VGA cable) is lying there hungry for input.

Now I am going to give the demodulated data to vga cable of monitor. Yes... I have impedence matched it to get it in to the corresponding voltage level of monitor. Then I fed it to the Blue input of VGA cable. Red and Green are left blank. So the display will be Blue and Black instead of Black and white.... Suppose I have grounded the signals well.... Now what is still required is sync signals. H-sync and V-sync to be fed to the corresponding pins of VGA cable.

You may think of a sync seperator from the input signal. No . I dont want that . Leave that option. I want to genearate the syncs externally. And I want a good range. 50-100 Hz for Vertical sync and 30-95KHz for H-sync. These signals will be supplied to their respective pins. Then I can see the display on the monitor. I can tune the Syncs to get perfect display.

So what I need is
1)To know whether this will work.(If this wont work, please tell how to teak this. Dont provide a complete alternative solution like RGB to VGA converter. I know that. What I need is a good range for sync tuning)
2)sync generating circuits with option for fine tuning in the specified range and volatage levels according to monitor.
3)I have a monochrome TV circuit set at hand(with option for V-Hold and H-Hold). Please tell how to tweak it to get the sync signals from it.

Thats it....


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fred47
Post subject: CRT issuePosted: Wed Feb 22, 2006 4:12 pm

General


Joined: Wed Feb 22, 2006 3:51 pm
Posts: 104
Hi,
Broadcast and consumer video is interlaced - only alternating lines are sent each field; two fields (one with the odd-numbered lines, one with the even-numbered lines) make up one frame of 525 linesw. This interlacing allows running the horizontal scanning frequency at 1/2 the rate that would be required with non-interlaced (called "progressive") scanning. So the resolution you get from a standard VGA monitor with a horizontal frequency of 31.5 kHz is equal to the resolution you get from standard TV at 15.75 kHz horizontal frequency. The tradeoff is that motion isn't as smooth on an interlaced-scan display as on a progressive-scan display.

One issue is that many computer monitors will not work well at a 15.75 kHz scanning rate - they're just not designed for it. (So check the specification for the monitor you're using).

Generating unlocked synchronizing signals: good luck - you'll need it! If you're off by a small percentage of the scan frequencies, the picture will roll or tear. It must be exact - which is why TV receivers all have a sync separator. Oh yes, extreme stability would also be required - no VCOs here!

You might want to re-think exactly what you want.

Good Luck!



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