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Re: AID: video question

From: Christian Klippel   ckmamalala.de
Date: Tue, 17 May 2005 09:54:05 -0700

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hello daniel,

Am Dienstag 17 Mai 2005 18:06 schrieb Daniel Arcé:
> : Sent via the Art Interface Device mailing list: aid@interaccess.org
> : Use your "Reply All" to  reply to the list, "Reply" for private response
>
> Dear aid list.
> I figured someone on this list would have the answer to my question:
>
> Briefly, I'm setting up live video feeds for a performance (3 live feeds).
> I need to somehow amplify a composite video signal so that I can
> distribute it to 3 monitors without losing the signal. Right now it drops
> after splitting it just once. I'm using those cheapy cmos wireless
> cameras, and I don't think the signal coming out of the receiver is very
> strong.
>


the problem is that a video input is terminated by a 75 resitance.
professional equipment allows you to switch that termination off if wanted, so 
one can connect more than one device.

> I thought the cheapest way would be to convert the a/v signal out of the
> camera to RF with an RF modulator, buying those '10dB amplifiers' for
> cable, running it across the room and splitting it, and convert the RF
> back to a/v. Would something like this work?
>
> Or is it cheaper to just get 3 video distribution amplifiers? Does anyone
> know who sells / rents them?
>

a video signal isnt that hard to handle. all you need are just three op-amps, 
configured to unity gain, and a 75 ohm resistor to give the input signal a 
termination. the op-amps of course need to be able to handle the frequency of 
a video signal. this one for example does a great job on this :
http://www.national.com/pf/LM/LMH6715.html

take a look into the datasheet, figure1 "non-inverting configuration...." is 
pretty much what you want. built that three time (or as many times as you 
want the signal to be split into), using a common input, but of course only 
put in the Rin resistor once.

> Thanks for thinking about this.
> Daniel.
>

hope that helped,

greets,

chris


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