RadioBanter - View Single Post

June 29th 05, 06:51 AM

In article . com,
says...

Hi all,

It's me again, attempting yet another mad science project, and I have
practically googled the subject to death before thinking of asking this
group for help:

I am wanting to put video (preferably color but will settle for
grayscale) onto a UHF TV channel for inhouse use only. I am
considering doing it as follows:

1) Convert output of a VGA card to composite video using resistive
combiner
(found a few on net).

And what magic resistive combiner makes VGA into NTSC??? There is
no such thing. There are active models which do this, but if your
VGA output is 640X480 or more, then NTSC will make the video suck.
NTSC does not have the bandwidth. Yes you can take a properly modulated
channel 3 signal, run it into a balanced mixer (well almost any mixer)
and add your favorite local oscillator signal and get 2 signals in
the uhf band. LO + ch3 and LO - ch3.

Good luck. Here's looking at ya or at least the unviewable signal.

2) Place composite video on VHF channel 3 using a game modulator.

3) Upconvert the video signal on VHF to UHF by with a local oscillator
whose frequence is the difference between the channels. I'd use an
active mixer circuit from the VHF/UHF part of the Handbook to do this.

4) To test functionality, attempt to tune in using either an analog TV
receiver or a TV tuner card.

Question is this:

Is point 3, upconverting video from VHF to UHF, a generally workable
technique?

Any other gotchas or pitfalls to my intended approach?

Thanks in advance,

The Eternal Squire