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CCTV SYSTEMS

Baluns and video amplifiers

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CCTV SYSTEMS

In yesterdays lesson we learned about the different cable types used in the CCTV industry.

CCTV systems can and often do utilize different signaling media throughout the cabling infrastructure.

When this happens we sometimes run into compatibility issues amongst different cable types.

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CCTV SYSTEMS

In some instances cable lengths can exceed manufactures recommendations and as an installer you need to provide solutions to address these problems.

Video baluns and amplifiers address these cabling issues.

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CCTV SYSTEMS

Balun is an acronym that stands for balanced/unbalanced.

A balun is an adapter that is an impedance matching device.

As it’s name suggests it can adapt twisted pair cabling to coax cabling and vice versa.

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CCTV SYSTEMS

These passive baluns accept one pair (100Ω) and convert it to coax (75Ω).

Twisted pair (UTP) is balanced transmission and coax is unbalanced transmission, in coax all of the signal is sent through the center conductor.

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CCTV SYSTEMS

Here is a passive video balun that accepts one CAT 5e/6 cable and provides 4 video outputs.

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CCTV SYSTEMS

Here are the specs for the same balun.

Power Requirements: None requiredVideo Format : NTSC, PAL, SECAM, CCIR(Color or B/W)BNC Resistance: 75ohmUTP Resistance: 100ohmTemperature: 0°C~55°C

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CCTV SYSTEMS

What is the difference between passive and active devices?

PASSIVE DEVICES DO NOT REQUIRE POWER AND ACTIVE DEVICES DO

ACTIVE BALUNS SERVE AS BOTH AN ADAPTER AND AN AMPLIFIER

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CCTV SYSTEMS

Signal attenuation is a problem over long distances and can be addressed using video amplifiers.

The key here is to keep the peak voltage the same at both ends of the link and reduce EMI and signal to noise ratios.

The typical signal voltage on a coax is 1V p-p (1 volt peak to peak).

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CCTV SYSTEMS

Attenuation, or signal loss can result anytime a signal propagates across a conductor and is measured in dB (decibels).

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CCTV SYSTEMS

Attenuation means the signal fades over distance and is no longer sufficient to drive a monitor or receiver.

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CCTV SYSTEMS

The effect shows up with RG-59 and RG-6 coax cable types as well as UTP (unshielded twisted pair) and custom cable options.

Each cable type introduces its own attenuation characteristics into the signal.

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CCTV SYSTEMS

An amplifier can amplify the 1V p-p signal to about 4 or 5V p-p to compensate for the voltage drop of a long cable run, however it will also amplify any unwanted noise.

Video amplifiers are available that have noise cancelling circuitry to address the problem.

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CCTV SYSTEMS

Amplified noise in a long cable run results in video images that are not discernible.

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CCTV SYSTEMS

There are two potential problems that can occur when connecting to multiple devices.

One problem is resistance.

The other problem is signal loss

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CCTV SYSTEMS

Signal loss problems can be solved by installing an active video amplifier between the camera and the monitoring unit.

Ideally the amp would be installed half way between camera and the head end.

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CCTV SYSTEMS

Using balun amplifiers it is possible to send a video signal over 1500 feet on CAT 3 cable.

For typical commercial CCTV installs active video baluns can usually meet any distance challenges using RG-59.

For ease of installation the video amplifier is usually placed at the head end.

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CCTV SYSTEMS

When we use the term head end we mean where all the equipment resides.

In many cases the head end will be the CCTV control room where the security guards sit in front of the monitors.

All cabling will be routed to a small closet next to monitoring stations.

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CCTV SYSTEMS

There are certain conditions that require multiple monitors to review the output from a single camera.

A distribution amplifier is a special post-equalizing amplifier.

It is used to connect more than one monitor to a camera output.

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CCTV SYSTEMS

Active baluns can be a very cost effective way of dealing with cabling issues.

We can extend the length of CAT 5e/6 lengths by the 3 times the standard distance of 328 feet.

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CCTV SYSTEMS

Consider what this balun can do…

Description: The VT98334T active video BALUN transceiver allows UTP wire to be run up to 12000 feet to a CCTV Camera.

BALUN Type: UTP Active Transceiver Module.Power In: DC12~24V or AC.Video Format: RS 170, NTSC, PAL, CCIR or SECAM .Wire Type: UTP Cat 2, 3, 4, 5e, 6; 12~24 AWG or

Heavier.Transmission dist.: 12000 Ft B/W / 9000 Ft color.

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CCTV SYSTEMS

As you have just seen an active balun amplifier can extend a UTP cable to 9000 feet, that is almost two miles.

We can achieve similar results over RG-59 using the same technology.

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CCTV SYSTEMS

Technical SpecificationModel Number GCH01Video Input Level 0.12 ~ 2V p-p 75 OhmVideo Output Level 1V p-p (Standard) 75 OhmInput Impedance 45 – 175 OhmInput Protection Surge ArrestorDisturbance Reduction >70dB @ 50HzVideo Bandwidth 50Hz - 5MHz (-3dB)Transmission Range Up to 1500 Metres (RG59B/U)Power Supply DC12V 150mA (Max)Dimensions (W x H x D) 138 x 32 x 76 mmWeight 130 GramsMaterial ABS Black

TECHNICAL SPECS FOR THE AMPLIFIER ON THE PREVIOUS SLIDE

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CCTV SYSTEMS

It should be noted that baluns are used in almost every facet of low voltage.

AUDIO BALUN, XLR TO TRS

TELEVISION BALUNS 300 Ω TO 75Ω

NETWORK BALUNS

TOLKEN RING BALUN 150Ω TO 100Ω