Can you use a 12G-SDI cable with 3G-SDI, HD-SDI or other lower-data-rate video equipment?

In general, yes. A professional 75-ohm coaxial cable assembly capable of supporting 12G-SDI can also be used to transport lower-rate SDI signals within the cable's performance limits.

But there is an important distinction:

The cable and the connected equipment perform different jobs. Understanding that difference makes it much easier to choose the correct SDI cable for a professional video system.

THE SHORT ANSWER

If you have a properly designed 12G-SDI cable assembly with the correct connectors, you can generally use that assembly for lower-rate SDI signals such as 6G-SDI, 3G-SDI, HD-SDI and SD-SDI.

Think of the cable's 12G capability as available transmission bandwidth.

A lower-data-rate signal does not require the cable to operate at its maximum capability.

For example, a short professional 12G-SDI BNC cable can be used between two compatible 3G-SDI devices.

The actual signal traveling through the cable remains 3G-SDI because that is what the connected equipment is transmitting and receiving.

CABLE COMPATIBILITY AND EQUIPMENT COMPATIBILITY ARE DIFFERENT

This is the most important concept to understand.

There are really two compatibility questions:

1. Can the cable transport the signal?
2. Can the equipment transmit and receive the signal format?

A cable capable of carrying 12G-SDI may also carry lower-rate SDI signals.

But a device with only a 3G-SDI input cannot automatically accept a 12G-SDI signal simply because you connect it with a 12G-rated cable.

The source and destination equipment must still support compatible video formats and SDI data rates.

WHAT DO 3G, 6G AND 12G MEAN?

The terms 3G-SDI, 6G-SDI and 12G-SDI refer to different generations and data rates within professional Serial Digital Interface video systems.

As the data rate increases, the transmission path becomes more demanding. Cable construction, connectors, termination quality and distance therefore become increasingly important.

CAN A 12G-SDI BNC CABLE CARRY 3G-SDI?

Yes.

A properly constructed professional 12G-SDI 75-ohm BNC cable can be used for a 3G-SDI connection.

If a 3G-SDI output is connected to a compatible 3G-SDI input, the signal remains 3G-SDI. The cable simply provides a transmission path capable of handling considerably higher bandwidth.

This can be useful when standardizing cable inventory.

Instead of maintaining completely separate short BNC patch cables for every SDI generation, a facility may choose to use appropriately rated higher-bandwidth assemblies in locations where they also meet the mechanical and distance requirements.

CAN A 12G-SDI CABLE CARRY 6G-SDI?

Yes. The same principle applies to 6G-SDI.

A cable assembly capable of supporting 12G-SDI at the required distance can also be used for a compatible 6G-SDI signal.

Again, the cable does not change the signal from 6G to 12G. It simply has sufficient transmission performance for the lower-rate signal.

CAN YOU USE 12G-SDI CABLE FOR HD-SDI?

Yes. A professional 12G-capable 75-ohm assembly can also be used in HD-SDI applications when the connector configuration is correct.

This is one reason 12G-rated cable assemblies can be useful when building new production systems that contain a mixture of legacy HD equipment and newer UHD equipment.

DOES A 12G CABLE CONVERT 3G-SDI TO 12G-SDI?

No.

A passive coaxial cable does not convert the SDI format.

Consider this example:

If format conversion is required, appropriate video processing or conversion equipment must perform that function.

WHAT IF ONE DEVICE IS 12G AND THE OTHER IS ONLY 3G?

This depends on the capabilities and configuration of the equipment—not the cable alone.

If a source is outputting a format that requires 12G-SDI and the destination accepts only 3G-SDI, simply installing a 12G cable between them does not make the devices compatible.

You may need to:

• Change the source output format
• Select a mutually supported SDI mode
• Use appropriate conversion equipment
• Verify the destination's supported formats

Always check the specifications for both devices when mixing equipment generations.

WHY 75 OHMS STILL MATTERS

Professional SDI video systems are designed around a 75-ohm coaxial transmission path.

That includes the cable and the connectors used in the signal path.

A connector may physically resemble another BNC connector while not necessarily being the correct choice for professional high-bandwidth video.

For SDI applications, use professional 75-ohm cable and connectors designed for the required data rate and coax construction.

DO YOU ALWAYS NEED THE LARGEST 12G CABLE?

No.

A higher SDI data-rate requirement does not automatically mean you need the physically largest coax cable available.

The appropriate cable depends heavily on distance and application.

For example, AV-Cables offers multiple professional coax constructions that can be used for different production requirements.

Mini RG59

A 12G-capable Mini RG59 construction can be particularly useful for short rack connections, patching and high-density equipment where smaller cable diameter is valuable.

RG59

Standard RG59 constructions provide another balance between cable size, handling and transmission distance.

RG6

Larger RG6 constructions can provide lower attenuation for longer SDI transmission paths.

See our Mini RG59 vs RG59 vs RG6 guide for a more detailed comparison.

DISTANCE STILL MATTERS

A cable being described as 12G-capable does not mean it will transport 12G-SDI over unlimited distance.

All coaxial cable introduces attenuation, and higher-data-rate signals generally have more demanding distance limitations.

This creates an important distinction:

When planning a UHD system, verify the expected 12G performance of the specific cable construction at the required length.

For more information, read How Far Can You Run 12G-SDI Cable?

WHAT ABOUT BNC, HD-BNC AND DIN 1.0/2.3?

SDI compatibility is not determined solely by the cable's coax construction.

The physical connector must also match the equipment.

Professional equipment may use:

• BNC
• HD-BNC
• DIN 1.0/2.3

HD-BNC and DIN 1.0/2.3 are often found on high-density professional video equipment where full-size BNC connectors would consume too much panel space.

AV-Cables offers HD-BNC cable assemblies as well as DIN 1.0/2.3 broadcast video cables for professional SDI applications.

SHOULD YOU BUY 12G CABLE FOR A 3G SYSTEM?

There are situations where doing so can make sense.

If you are installing or upgrading a production system and expect equipment to migrate toward 12G-SDI, using suitable 12G-capable assemblies in appropriate locations can reduce the number of cables that may need to be replaced later.

It can also simplify spare-cable inventory when the same assemblies can serve multiple SDI applications.

However, cable selection should still consider:

• Required distance
• Cable diameter
• Flexibility
• Rack density
• Connector type
• Installation environment
• Budget

The highest-rated cable is not automatically the best physical cable for every installation.

SDI COMPATIBILITY QUICK GUIDE

THE BOTTOM LINE

A professional 12G-SDI cable can generally be used to transport 6G-SDI, 3G-SDI, HD-SDI and lower-rate SDI signals.

What it cannot do is upgrade the capabilities of the equipment connected to it.

The cable must have sufficient performance for the required signal and distance, while the source and destination devices must support compatible SDI formats.

For mixed-generation broadcast systems, choosing suitable 12G-capable assemblies can provide useful flexibility while helping prepare portions of the cabling infrastructure for UHD workflows.

PROFESSIONAL SDI CABLES FROM AV-CABLES

AV-Cables manufactures professional 75-ohm SDI cable assemblies for broadcast, live production, studios, fly packs, mobile production, houses of worship, corporate AV and systems integration.

Available configurations include Mini RG59, RG59 and RG6 coax as well as BNC, HD-BNC and DIN 1.0/2.3 connectivity for professional SDI systems.

AV-Cables professional cable assemblies are hand assembled in the USA and individually tested before shipment.

AV-Cables — Professional Broadcast Connectivity Solutions