When specifying a coaxial cable for your RF system, security camera, or antenna installation, you’ve likely encountered the term impedance—typically marked as 50Ω or 75Ω. But what does impedance really mean in this context? And how does it impact your signal transmission?
In this guide, we’ll break down the concept of impedance in coaxial cables, compare 50 ohm vs. 75 ohm systems, and help you choose the right cable for your application—whether you’re working with RF transmission lines or AV installations.
What Is Impedance in a Coaxial Cable?
Impedance, in the world of coaxial cables, refers to the “characteristic impedance” (Z₀)—a measure of resistance to alternating current (AC) signal flow along the cable. It’s expressed in ohms (Ω) and is not the same as DC resistance.
What Determines Impedance?
Impedance depends on the physical construction of the coax cable:
- Diameter of inner conductor
- Dielectric material and thickness
- Outer conductor (shield) diameter
Formula:
Z₀ = √(L/C)
Where L = inductance per unit length, C = capacitance per unit length
This means the electrical field distribution within the coaxial geometry defines how much opposition the cable presents to signal flow, especially at high frequencies.
The Two Common Impedance Values: 50 Ohm vs. 75 Ohm
The two standard impedances in coaxial systems are:
50 Ohm Coax
- Originated from early radio transmission lines as a balance between power handling and low attenuation
- Used for RF transmission, Wi-Fi, cellular, antennas
75 Ohm Coax
- Optimized for low signal loss, especially in video and data
- Common in TV, CCTV, satellite, SDI broadcast
Comparison Table
| Parameter | 50 Ohm Cable | 75 Ohm Cable |
|---|---|---|
| Common Types | RG58, RG174, RG213 | RG6, RG59 |
| Typical Use | RF antennas, test gear | TV, CCTV, broadband |
| Attenuation (loss) | Slightly higher | Lower over long distances |
| Power Handling | Higher (up to 2kW+) | Lower (typ. <100w) |
| Impedance Matching | With RF systems | With video/audio receivers |
In summary: 50Ω = Power & RF. 75Ω = Clarity & AV.
Why Impedance Matching Matters
Correct impedance matching between your cable, source, and load is vital to ensure efficient signal transfer.
When impedance is matched:
- Minimal signal reflection
- High signal integrity
- Low VSWR (Voltage Standing Wave Ratio)
When impedance is mismatched:
- Reflections occur → signal distortion
- Loss of power or image artifacts
- Possible damage to RF components
Especially in high-frequency or high-power systems, even a small mismatch (e.g. 50Ω to 75Ω) can cause significant performance loss.
How to Choose the Right Impedance for Your Application
Still wondering which coaxial cable impedance fits your needs? Use this table as a quick reference:
Application vs. Impedance Guide
| Application Type | Recommended Impedance |
|---|---|
| Wi-Fi, Cellular, Ham Radio | 50Ω |
| CCTV Analog (DVR) | 75Ω |
| Satellite TV | 75Ω |
| Antenna Feedlines (RF) | 50Ω |
| Broadcast SDI Video | 75Ω |
| RF Test Benches | 50Ω |
Quick Test: What Type Do You Need?
Ask yourself:
- Are you powering or transmitting RF energy? → Use 50Ω
- Are you carrying video or AV signal over distance? → Use 75Ω
Can You Mix 50 Ohm and 75 Ohm Coax Cables?
Technically possible, but generally not recommended.
| Scenario | Impact |
|---|---|
| 50Ω cable to 75Ω equipment | Signal reflection, low efficiency |
| 75Ω cable in 50Ω RF system | Higher VSWR, potential mismatch |
| Using impedance adapter (e.g., BNC) | Mitigates mismatch, not perfect |
Always aim for uniform impedance across cable, connector, and equipment.
Bafitop’s Coaxial Cable Solutions for 50Ω and 75Ω Systems
At Bafitop, we manufacture and supply coaxial cables for both RF and AV system integrators. Below are our top solutions:
| Product Code | Impedance | Cable Type | Typical Application |
|---|---|---|---|
| BFT-RG58 | 50Ω | RG58 | Antennas, routers, GPS |
| BFT-RG174 | 50Ω | RG174 | IoT, RF modules, test leads |
| BFT-RG59 | 75Ω | RG59 | CCTV analog, composite video |
| BFT-RG6 | 75Ω | RG6 | Satellite TV, DVB-T, HDTV |
All cables come with braided shielding, UV-resistant jackets, and support custom length / terminated assemblies.
📧 Email us: sales@bafitop.com
📞 Phone: +86-15817341810
FAQs About Coaxial Cable Impedance
Q1: What happens if I connect 50 Ohm cable to 75 Ohm equipment?
You may experience reflections, signal loss, or video/audio degradation. Always match impedance where possible.
Q2: Can I measure cable impedance with a multimeter?
No. Impedance is an AC property. You need a Time Domain Reflectometer (TDR) or Vector Network Analyzer (VNA) to measure it properly.
Q3: Does cable length affect impedance?
No, characteristic impedance is constant along the cable. However, longer cables increase attenuation (signal loss), not impedance.
Not Sure Which Impedance You Need? We’re Here to Help.
Whether you’re sourcing cables for a data center, RF antenna, or video backbone, our team is ready to guide your selection.
📧 Contact us: sales@bafitop.com
📞 Call: +86-15817341810
🎯 Request samples or a custom quote today.
