Bnc to VGA query

[eamon]

Hi all

 

I am the resident technician in a venue. I have been slowly building up the infrastructure as the time goes on.

 

I have recently added in some video lines. These are 5way BNC Plugs & 1 x cat 5e connection to each corner(DSR & DSL). The cat 5 is fine, terminated & poses no problems.

 

I have checked each Bnc line with a composite signal from a DVD player to a tv. All ten connections work fine and displayed a good clean picture.

 

The cables used is RG179.

 

My problem is when I hook up a laptop (mac mini display to VGA) and use the VGA to 5 way BNC adaptors to connect to a projector onstage, I get very intermittent results. Sometimes I have a clear image, sometimes I don't.

 

The max length of cable is 50m.

 

I get the feeling that the rg179 is not able to handle the "bandwidth" required. Am I right?

 

Does any body know see any obvious thing in my setup?

 

Cheers

 

Eamon

 

I have checked all the cables involved, projector is on the right source, re-started all etc but can't get a consistent signal.

[pjrails]

HI

Your cable lengh personally I feel is a bit long without any form of amplfication/booster, are you also returning the BNC's back to a VGA 15 pin to go back in the projector, because that might also be a problem as you may not be sending the sync signal to the projector, at my venue we have a 33 mtr VGA run to our auditroium projector and we found that without an amplfier the signal was poor but with one we got full signal. You could try to send your VGA down the cat 5 with the convertor units we do this if we need a projector on stage rather than in the auditorium which is nearly 75mtrs and we have no problem doing the Cat 5 way

Hope this helps

PJ

[David Lee]

I get very intermittent results. Sometimes I have a clear image, sometimes I don't.

 

How is it intermittent? The first check would be that H and V syncs are the correct way around on both breakout cables (vga to 5 BNCs). If not marked then you find that they can be laid flat and the cores will usuallygo RGBHV from the breakout cable. If the VGA breakout cables are the ones with VGA connector to thin cables to BNCs then these are very fragile, especially when dragged out of a pile of cable in a flight case.

[eamon]

Hi all

 

Many thanks for the replies

 

I had checked the 5way BNC to VGA adaptors cable earlier this year and had verified they were working. I will double check as you never know!

 

I will check out your suggestion re the HV sync. I have a multitude of colours so that may be an issue I am missing. I had been sticking to a convention of RGB H(black) & V(yellow) but will double check etc.

 

I dont have the budget left to buy the cat 5 to vga baluns. I intend purchasing them in the new year. It gives me the option to hook up 4 x projectors without re-inventing the wheel etc.

 

 

many thanks

 

 

eamon

[eamon]

Hi all

 

Just to update and finish this topic off.

 

All my video lines are up and working now. David Lee was correct in that the issue of the layout was in the Horizontal & vertical sync cables.

 

That is rectified and all is working.

 

Many thanks to all for your help

 

 

cheers

 

eamon