Running Long Cable at DVinfo.net

Rick Step · March 20th, 2006, 09:02 PM

If I needed to run a BNC cable for say, 600 ft from a camera to a dv deck that would record the footage...how would I go about that? Do I need to amplify the signal or is this even possible?

Thanks

Rick

Andrew Khalil · March 21st, 2006, 08:46 AM

if you use high grade cable that is intended for long runs, you should be fine. I'm not sure if you'llneed a distribution amp or not, but I've run BNC for 300 feet and it looks fine, the key is to use good cable.

Rick Step · March 21st, 2006, 11:05 AM

thanks andrew,

Any suggestions for where to look for high end cables? Do you know how long they make them?

Rick

Andrew Khalil · March 21st, 2006, 11:10 AM

pretty much any professional audio/video supplier should have them and they are usually sold in bulk (1000ft) which is good because you need a lot. Your best bet is to use BNC cable and just adapt the ends to whatever you need. 2 brands we've used around our building are Delco and Canare and both have excellent reputations (but I don't know if I spelled either correctly, but I'll double check it for you).

A. J. deLange · March 21st, 2006, 04:27 PM

Bes sure to obtain 75 ohm cable and that the shield has a high percentage coverage to prevent noise pickup and radiation.

Rick Step · March 21st, 2006, 05:08 PM

Thanks guys...lets say I get the 75ohm top of the line cable that runs 600 or 1000 feet. How much quality loss am I going to get? Is it going to look drastically different than a capture to tape?

I'm broadcasting this over the internet so it gets huge compression anyway. Do you guys have a feel for how bad this is going to be?

Rick

A. J. deLange · March 21st, 2006, 07:40 PM

The problem with runs as long as 1000 feet is that losses are going to be pretty hefty at the higest video frequencies. A good RG-59 cable (double shield, 98% coverage, 0.313" OD) is rated at 12 dB loss for 1000 feet at 20 MHz. At 6 MHz that implies a loss of about 6.6 dB which means over half the signal voltage but only 3 db (30% voltage loss) at 1 MHz. This "tilt" may result in some problems with the received signal. It is usual in cases where a long run is required to modulate the signal on a carrier so that this tilt is eliminated. You will just have to experiment to see what he capabilities of your recorder are. It may have automatic gain adjustment and and equalizer (less likely) and do just fine. Or it may not.

Brian Farris · March 21st, 2006, 07:53 PM

We bought 100ft cables from Wal-Mart and joined them together with couplers. After about 400 ft, the picture gets a kind of ghosting effect and we have to use an amplifier.

So.... don't get your coax from wal-mart.

Rick Step · March 27th, 2006, 01:17 AM

hahaha,

I'll see if target has something better!

Rick

March 20th, 2006, 09:02 PM	#1
Rick Step Regular Crew Join Date: Jun 2004 Location: Virginia, USA Posts: 62	Running Long Cable If I needed to run a BNC cable for say, 600 ft from a camera to a dv deck that would record the footage...how would I go about that? Do I need to amplify the signal or is this even possible? Thanks Rick

March 21st, 2006, 08:46 AM	#2
Andrew Khalil Major Player Join Date: Jun 2005 Posts: 424	if you use high grade cable that is intended for long runs, you should be fine. I'm not sure if you'llneed a distribution amp or not, but I've run BNC for 300 feet and it looks fine, the key is to use good cable.

March 21st, 2006, 11:05 AM	#3
Rick Step Regular Crew Join Date: Jun 2004 Location: Virginia, USA Posts: 62	thanks andrew, Any suggestions for where to look for high end cables? Do you know how long they make them? Rick

March 21st, 2006, 11:10 AM	#4
Andrew Khalil Major Player Join Date: Jun 2005 Posts: 424	pretty much any professional audio/video supplier should have them and they are usually sold in bulk (1000ft) which is good because you need a lot. Your best bet is to use BNC cable and just adapt the ends to whatever you need. 2 brands we've used around our building are Delco and Canare and both have excellent reputations (but I don't know if I spelled either correctly, but I'll double check it for you).

March 21st, 2006, 04:27 PM	#5
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	Bes sure to obtain 75 ohm cable and that the shield has a high percentage coverage to prevent noise pickup and radiation.

March 21st, 2006, 05:08 PM	#6
Rick Step Regular Crew Join Date: Jun 2004 Location: Virginia, USA Posts: 62	Thanks guys...lets say I get the 75ohm top of the line cable that runs 600 or 1000 feet. How much quality loss am I going to get? Is it going to look drastically different than a capture to tape? I'm broadcasting this over the internet so it gets huge compression anyway. Do you guys have a feel for how bad this is going to be? Rick

March 21st, 2006, 07:40 PM	#7
A. J. deLange Major Player Join Date: Jun 2004 Location: McLean, VA United States Posts: 749	The problem with runs as long as 1000 feet is that losses are going to be pretty hefty at the higest video frequencies. A good RG-59 cable (double shield, 98% coverage, 0.313" OD) is rated at 12 dB loss for 1000 feet at 20 MHz. At 6 MHz that implies a loss of about 6.6 dB which means over half the signal voltage but only 3 db (30% voltage loss) at 1 MHz. This "tilt" may result in some problems with the received signal. It is usual in cases where a long run is required to modulate the signal on a carrier so that this tilt is eliminated. You will just have to experiment to see what he capabilities of your recorder are. It may have automatic gain adjustment and and equalizer (less likely) and do just fine. Or it may not.

March 21st, 2006, 07:53 PM	#8
Brian Farris Regular Crew Join Date: Jun 2005 Location: Hattiesburg, MS Posts: 99	We bought 100ft cables from Wal-Mart and joined them together with couplers. After about 400 ft, the picture gets a kind of ghosting effect and we have to use an amplifier. So.... don't get your coax from wal-mart.

March 27th, 2006, 01:17 AM	#9
Rick Step Regular Crew Join Date: Jun 2004 Location: Virginia, USA Posts: 62	hahaha, I'll see if target has something better! Rick