Coax Cable: Impedance First, Then Loss
Quick answer / TL;DR: Short answer: use RG6 for satellite, cable TV and MoCA, RG11 for longer 75 ohm runs, and 50 ohm types such as RG58 or LMR for radio and instrumentation. Choose quad shield for noisy routes, compression F connectors for permanent installs, and check loss at your highest frequency rather than at DC.
Three coaxial families: BNC for CCTV, F-type for TV, N for RF – each with its impedance.Coaxial cable comes in two impedances that serve different worlds: 75 ohm for video and broadcast, 50 ohm for radio and test.
Mixing them causes reflections that look like loss rather than an obvious fault.
Types by Application
| Cable | Impedance | Use |
|---|
| RG6 | 75 ohm | Satellite, CATV, MoCA |
| RG11 | 75 ohm | Long 75 ohm runs |
| RG59 | 75 ohm | Short analogue video |
| RG58 | 50 ohm | Short RF leads |
| LMR-400 | 50 ohm | Low-loss RF runs |
Loss rises with frequency, so a cable adequate at 100 MHz may be unusable at 2.4 GHz.
Shielding and Connectors
- Quad shield for noisy routes
- Compression connectors, not twist-on
- Match connector to cable diameter
- Weatherproof outdoor joints
- Respect bend radius
Twist-on connectors are the largest single cause of ingress in domestic installations.
Real-World Applications
A satellite receiver 25 m from the dish uses RG6 throughout. A rooftop antenna at 400 MHz uses LMR-400 for lower loss over 20 m.
Standards and Verification
| Reference | Relevance |
|---|
| IEC 61196 | Coaxial cable |
| IEC 61169 | RF connectors |
| SCTE | Distribution practice |
Loss curves for a specific cable are not provided in the knowledge base. Use the manufacturer's data at your frequency.
References
- IEC 61196-1, Coaxial communication cables
- IEC 61169 series, RF connectors
- SCTE operational practices
Practical Notes
Label 50 and 75 ohm cables differently. They look alike and only one belongs in each system.
Related reading: coax cable — blogs/news/coax-cable
Related reading: coax to coax cable — blogs/news/coax-to-coax-cable
Related reading: subwoofer coax cable — blogs/news/subwoofer-coax-cable
Frequently Asked Questions
RG6 or RG59?
RG6 for anything beyond short analogue runs.
Does impedance matter?
Yes. Mixing 50 and 75 ohm causes reflections.
Which connector?
Compression F for permanent installs.
When use RG11?
Long 75 ohm runs where loss is critical.
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