50 Ohm vs 75 Ohm Coaxial Cable: What's the Difference and Which Should You Use?
Two coaxial cables can look almost identical while being designed for very different signal systems. One of the most important differences is their characteristic impedance, with 50 ohm and 75 ohm being the two most common values used in RF, wireless, test, video, and broadcast applications.
In general, 50 ohm coaxial cable is widely used for RF, antennas, wireless communication, and test equipment, while 75 ohm coaxial cable is commonly used for video, broadcast, CATV, CCTV, and SDI transmission.
The correct choice depends on the impedance specified by the equipment and the complete signal path-not simply on the appearance of the connector. Premier Cable supplies RF coaxial cable assemblies using SMA, BNC, TNC, N-Type and other RF interfaces for standard and custom applications.
What Does 50 Ohm or 75 Ohm Mean in a Coaxial Cable?
The 50Ω or 75Ω rating of a coaxial cable refers to its characteristic impedance. This impedance is determined by the geometry and electrical properties of the cable, including the center conductor, dielectric material, outer conductor, and the dimensions between these elements.
Characteristic impedance should not be confused with ordinary DC resistance. Measuring a short piece of coaxial cable with a multimeter will not simply produce a reading of 50 or 75 ohms. Instead, characteristic impedance describes how the transmission line behaves when carrying alternating or high-frequency signals.
For reliable transmission, the source, cable, connectors, adapters, and load should normally be designed around the same nominal impedance. When different impedances are introduced into the same signal path, part of the signal can be reflected rather than transmitted efficiently.
50 Ohm vs 75 Ohm Coaxial Cable: Quick Comparison
| Feature | 50 Ohm Coax | 75 Ohm Coax |
|---|---|---|
| Typical Applications | RF, antennas, wireless, radio, test equipment | Video, broadcast, SDI, CATV, CCTV |
| Common Interfaces | SMA, TNC, N-Type, 50Ω BNC | 75Ω BNC, HD-BNC, DIN 1.0/2.3 |
| Common Cable Families | RG58, RG174, RG178, RG316 | RG59, RG6, professional video coax |
| Typical Equipment | RF instruments, antennas, radios, wireless modules | Cameras, monitors, broadcast and video equipment |
| Selection Principle | Match the impedance required by the equipment and maintain it through the complete signal path. | |
What Is 50 Ohm Coaxial Cable?
50 ohm coaxial cable is widely used in RF and wireless systems. It provides a practical balance between power handling and signal attenuation, which helped establish 50Ω as a common impedance for RF transmitters, receivers, antennas, test instruments, and communication equipment.
Typical 50 ohm applications include:
- RF antennas and radio equipment
- Wi-Fi and wireless communication systems
- GPS and cellular equipment
- RFID systems
- RF test and measurement equipment
- Industrial wireless systems
Common 50Ω interfaces include SMA, TNC, N-Type, and 50Ω BNC configurations.
Common 50 Ohm Coaxial Cable Types
Impedance is only one part of cable selection. Cable diameter, attenuation, flexibility, operating frequency, routing space, and required length must also be considered.
RG58
A widely used 50Ω coaxial cable for RF equipment, antennas, communication systems, and general-purpose RF cable assemblies.
RG174
A thin and flexible cable often used where equipment space is limited or compact cable routing is required.
RG316
A compact 50Ω coaxial cable commonly used for RF pigtails, internal equipment connections, and small-diameter cable assemblies.
50 Ohm Systems Can Use Different RF Connectors
Connector type and characteristic impedance are related specifications, but they are not the same thing. A 50Ω RF system does not need to use identical connector families at both ends of the cable.
For example, equipment with an SMA interface can be connected to equipment with a 50Ω BNC interface using an SMA male to BNC male RG58 coaxial cable .
In this case, the connector family changes from SMA to BNC, but the cable assembly can still maintain a nominal 50Ω signal path. Similar configurations are possible between SMA, TNC, N-Type, BNC, and other RF interfaces when the connectors and cable are specified for the same impedance.
Why Do RF Systems Commonly Use 50 Ohms?
There is no single coaxial impedance that provides the best possible performance in every category. The impedance associated with maximum power handling is different from the impedance that provides minimum attenuation.
The 50Ω standard represents a practical engineering compromise between these characteristics. As RF technology developed, 50Ω became widely adopted across transmitters, receivers, RF instruments, antennas, and radio communication equipment.
This is why many signal generators, spectrum analyzers, wireless modules, antennas, and other RF devices specify a 50Ω interface. The cable connecting these devices should normally maintain the same impedance.
Common Applications for 50 Ohm RF Cable Assemblies
Because 50Ω is widely used across RF systems, the same nominal impedance can appear with many different connector families and cable constructions.
Typical applications include:
- External antenna connections
- Wireless routers and communication equipment
- GPS and GNSS systems
- RFID equipment
- RF test instruments
- Industrial radio systems
Larger threaded connectors such as N-Type are often used for antenna and wireless equipment, while TNC provides a threaded RF interface for applications where secure mating is required.
What Is 75 Ohm Coaxial Cable?
75 ohm coaxial cable is widely used for video and broadband signal transmission. Compared with the typical 50Ω RF environment, 75Ω systems are particularly common in broadcast facilities, professional video equipment, CATV networks, CCTV systems, and SDI infrastructure.
Coaxial transmission lines around 75Ω can provide favorable attenuation characteristics, helping make this impedance suitable for signal-distribution applications. Over time, 75Ω became an established standard for television and professional video transmission.
Important: A BNC connector is not automatically a 50Ω connector. BNC interfaces are manufactured for both 50Ω RF systems and 75Ω video systems.
50 Ohm vs 75 Ohm BNC Connectors
BNC is one of the most common sources of confusion when comparing 50Ω and 75Ω systems because the same general bayonet-style connector family is used in both RF and professional video applications.
Are 50 Ohm and 75 Ohm BNC Connectors the Same?
No. Although 50Ω and 75Ω BNC connectors may have a similar external appearance, they are designed for different electrical environments. Their internal geometry and dielectric construction can differ in order to maintain the intended characteristic impedance.
Some versions may physically mate, but mechanical compatibility does not guarantee electrical compatibility. This becomes increasingly important as operating frequency or video data rate increases.
How Can You Tell Whether a BNC Connector Is 50 or 75 Ohms?
Check the following:
- Connector manufacturer specification
- Equipment datasheet
- Cable type and impedance
- Connector part number
- Signal standard or intended application
Connector appearance alone should not be used to determine impedance. View BNC coaxial cable assemblies for different RF and video cable configurations.
Can You Use a 50 Ohm Cable in a 75 Ohm System?
For a properly designed RF or video transmission path, the preferred approach is to maintain the impedance specified by the equipment throughout the system. Using a 50Ω cable in a 75Ω system-or a 75Ω cable in a 50Ω system-creates an impedance discontinuity.
Possible effects include:
- Signal reflections
- Reduced return loss performance
- Higher VSWR in RF systems
- Reduced signal integrity
- Reduced transmission margin in high-frequency or high-data-rate systems
This does not mean that every mismatched connection will immediately stop working. The actual effect depends on frequency, cable length, signal bandwidth, equipment tolerance, and the number and severity of impedance discontinuities. However, a matched system provides more predictable performance.
Can You Connect 50 Ohm and 75 Ohm Equipment?
Mechanical Compatibility
Two connectors may physically mate or may be connected with an adapter. This only establishes a mechanical connection between the interfaces.
Electrical Compatibility
A physical connection does not automatically provide impedance matching. A standard RF adapter changes the connector interface but should not be assumed to convert a 50Ω system into a correctly matched 75Ω system.
75 Ohm Coaxial Cable in Professional Video Systems
Professional video systems use coaxial transmission for signals such as SDI, where maintaining the specified signal path is particularly important at high data rates.
Depending on the equipment and installation density, professional video systems may use interfaces such as 75Ω BNC, HD-BNC, or DIN 1.0/2.3.
One example available from Premier Cable is the DIN 1.0/2.3 to HD-Micro BNC 12G SDI video cable , designed for professional video equipment using compact coaxial interfaces.
This illustrates an important point: two assemblies may both use coaxial cable construction, but an RF antenna cable and an SDI video cable are designed around different system requirements. The intended signal standard should therefore be confirmed before selecting the cable.
How to Choose Between 50 Ohm and 75 Ohm Coaxial Cable
1. Check the Equipment Impedance
Start with the device specification. RF ports, antennas, test instruments, cameras, and video equipment normally specify the impedance required at their signal interfaces.
2. Identify the Connector Interface
Determine the connector family, gender, and mounting style. Common interfaces include SMA, BNC, TNC, N-Type, DIN 1.0/2.3, and HD-BNC.
3. Check the Frequency or Signal Standard
RF frequency, video data rate, and transmission distance affect cable and connector performance. A cable suitable for one application may introduce excessive attenuation or signal degradation in another.
4. Select the Appropriate Coaxial Cable
Compare impedance, attenuation, cable diameter, shielding, flexibility, operating frequency, and required length rather than choosing a cable based only on its connector or RG designation.
5. Confirm the Mechanical Requirements
Check whether the installation requires straight or right-angle connectors, male or female interfaces, bulkhead mounting, compact routing, a specific cable diameter, or environmental protection.
Custom RF Coaxial Cable Assemblies
When a standard cable does not match the equipment interface or installation requirements, a custom coaxial cable assembly can be designed around the actual electrical and mechanical specifications of the system.
Common customization options include:
- Specified impedance
- SMA, BNC, TNC, N-Type and other RF connectors
- Male or female connectors
- Straight or right-angle orientation
- Bulkhead or panel-mount configurations
- Coaxial cable type
- Custom cable length
- Shielding and jacket requirements
- Application-specific frequency or signal requirements
View more RF coaxial cable assemblies or provide the connector types, impedance, cable length, equipment specifications, and application requirements for a custom configuration.
Frequently Asked Questions
Is RG58 50 ohm or 75 ohm?
Standard RG58 coaxial cable is a 50Ω cable commonly used in RF, radio, antenna, communication, and test applications.
Is BNC 50 ohm or 75 ohm?
BNC connectors are available in both 50Ω and 75Ω versions. 50Ω BNC interfaces are widely used in RF and test systems, while 75Ω BNC interfaces are common in video and broadcast applications.
Is SMA 50 ohm or 75 ohm?
Standard SMA connectors used in RF and wireless applications are predominantly designed for 50Ω systems. The actual connector and equipment specification should still be checked before selecting a cable assembly.
Can a 50 ohm BNC connector connect to a 75 ohm BNC connector?
Some 50Ω and 75Ω BNC designs may physically mate, but mechanical compatibility does not mean the signal path is correctly impedance matched. For RF and high-speed video applications, use connectors and cables designed for the impedance specified by the equipment.
What happens if coaxial cable impedance does not match?
An impedance mismatch can cause signal reflections and reduce signal integrity. In RF systems it can affect return loss, VSWR, and power transfer, while high-speed video systems can experience reduced transmission margin and signal degradation.
Which is better, 50 ohm or 75 ohm coaxial cable?
Neither impedance is universally better. 50Ω is the established standard for many RF and wireless systems, while 75Ω is widely used for video and broadcast transmission. The correct choice is the impedance specified by the system.
Conclusion
The main difference between 50 ohm and 75 ohm coaxial cable is not simply cable size or connector appearance-it is the electrical system the cable is designed to support.
50Ω coaxial cable is widely used for RF, antennas, wireless communication, and test equipment, while 75Ω coaxial cable is commonly used for professional video, broadcast, CATV, CCTV, and SDI transmission.
Before choosing a coaxial cable assembly, confirm the equipment impedance, connector type, frequency or signal standard, cable length, and installation requirements. Maintaining consistent impedance through the signal path helps provide more predictable and reliable transmission performance.
