VGA to RF coax

[Peter]

[COLOR="DimGray"]Overview
The Apple DVI to Video Adapter

Is it possible to use this adaptor (second output) together with dvi-vga on the first output for monitoring purpuses during rehearsal (reprogramming)?

Wouldnt i be better of with composite?

Can i mix RF tv's with composit tv's without seeing the difference in image quality?

Thanks again!

[Marty Postma]

Can i mix RF tv's with composit tv's without seeing the difference in image quality?

RF is really just a different plug for the same signal type as RCA composite...you won't see a difference between the two, but in my experience RF cables do seem to be more prone to signal interference from power lines etc.

[SourceChild]

RF is really just a different plug for the same signal type as RCA composite...you won't see a difference between the two, but in my experience RF cables do seem to be more prone to signal interference from power lines etc.

Marty,

You are correct that both are RF signals. However, a "cable" signal traveling down RG Coax is very different from Composite Video.

The impedance is different between the Coax used in RG cable and the coax used as a shield in RCA or BNC type composite.

The "Radio Shack" type RCA cable is low quality with a lower resistance. The wires are stranded and very much more catering to voltage transmission than to RF transmission. (Basically crap but okay in small runs)

75 Ohm Video cable with BNC termination is specifically designed to transport the "video range" spectrum of RF signals. The tolerance of it is exceedingly higher than anything else. It also has much tighter twisted center wire, or solid copper.

Regular old RG6 type coax cable is solid core copper which means it is much better as a transmission medium for the modulating frequencies of VHF and UHF. In fact, it was designed specifically to transmit the ranges known as VHF. The shield diameter is larger that High quality 75 Ohm cable. The larger dia allows the sub harmonics to pass through the shield to eliminate ghosting sub harmonic reflections. Whereas in pro video cable, the shield is much tighter to enhance the filtering of electric fields and magnetic transients.

Another thing to mention is the nature of the difference between VHF and CVBS. Composite called CVBS (or Color, Video, Burst, Sync composition) is an RF signal where the scan rates are frequency and amplitude based. VHF however performs a frequency modulation of CVBS so that it can be encoded to a specific frequency channel for amplification and transmission.

Another way to think of it is that you need a tuner to use RF. RF has audio multiplexed with it.

[SourceChild]

I like Emiliano's idea.

Just make absolutely sure to put an isolated signal amp between the cable run and the adapter because the slightest little spike or any noise will fry your video card.

[Peter]

I like Emiliano's idea.

Just make absolutely sure to put an isolated signal amp between the cable run and the adapter because the slightest little spike or any noise will fry your video card.

So something like the kramer vm-25, http://kramerelectronics.com/indexes...sp?name=VM-25?

[SourceChild]

So something like the kramer vm-25, http://kramerelectronics.com/indexes...sp?name=VM-25?

Good choice. The 1021 is also fine. The point is to have a filtering device in the path. Even if you had a single TV you were driving. It's always good practice to use some sort of "gatekeeper."

Similar to the way you typically always have an opto-splitter at your stage rack for DMX.

[Peter]

So i would also get away with a kramer pt102vn?

[Peter]

Just make absolutely sure to put an isolated signal amp between the cable run and the adapter because the slightest little spike or any noise will fry your video card.

What's the reason for that? Because i dont understand, my next question would be : is it the same for VGA? Now i connect graphics to splitter/booster and then to the projector.

[SourceChild]

What's the reason for that? Because i dont understand, my next question would be : is it the same for VGA? Now i connect graphics to splitter/booster and then to the projector.

Chances are you'll be fine but when you plug a string of video devices together, you run the risk of noise and feedback. Some noise is okay but even if you don't visual see it, there could be damage done to your video cards as they are more delicate than other components in the chain. The isolated splitter is a good idea to protect your gear the same way you would use a surge protector.

it's not necessary though.

[emilianomorgia]

Is it possible to use this adaptor (second output) together with dvi-vga on the first output for monitoring purpuses during rehearsal (reprogramming)?

Wouldnt i be better of with composite?

Can i mix RF tv's with composit tv's without seeing the difference in image quality?

Thanks again!

i'm on a show rightnow . Mac pro 3 Giga xt1900
first output 1024x768
second apple video adaptor ....

The good news is I've switch from a FOLSON converter ( 3000 euro ) to the video adaptor ( 19 euro ) with no different on the final result