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ben_indo

Twisted Pair - Shielded or Unshielded

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Dear Forum;

 

Should I use shielded twisted pair for CCTV transmission in area where power cables are near by ? or I just can just use a unshielded twisted pair ...

 

Kindly give suggestions.

 

Ben

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Always use unshielded twisted pair (UTP) cable.

 

Each pair cannot have a foil shield or system will not function. An overall cable foil shield is ok.

 

Good luck!

 

Cheers......Rapid

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hi Rapid, Thanks for your info

btw, do you know the reason behind why STP (with individual pair foil wrap) type not working ? I find that most literatures are not recommend shielded pair for CCTV application, I just don't know why, any idea ?, anyone ?

 

Ben

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hi Rapid, Thanks for your info

btw, do you know the reason behind why STP (with individual pair foil wrap) type not working ? I find that most literatures are not recommend shielded pair for CCTV application, I just don't know why, any idea ?, anyone ?

 

Ben

Bigger cable capacity.

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Hi ben_indo.....copied this from the NVT www.nvt.com website.

 

Can shielded twisted pair be used?

 

Some customers have successfully used shielded wire up to a few hundred feet. However NVT does not recommend it. Its high-frequency roll-off will severely degrade the distance performance. Use of an amplified receiver can compensate for some signal loss. Multi-pair wire (six pairs or more) can have an overall shield without degradation.

 

Coax is an unbalanced method of transmission...

UTP is a balanced method of transmission...

 

Common Mode Rejection is the ability of a balanced input to reject the part of the incoming signal which has the same amplitude and phase on both input terminals, referenced to ground (The ability to respond to only differences at the input terminals).

 

The original signal has a positive part on one termination and a negative part (opposite polarity) on the other.

 

Any signal 'common' to both terminals will eventually get rejected, cancelled at the receiving end.

 

The use of shielding would inhibit the effectiveness of CMR.

 

Sorry to go technical on you.

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Dear Rapid;

 

Thank you for your detailed replies;

sometime or rather most of the time we need to go technical to satisfied curious minds.

 

Ben

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