In RF system design, one parameter that consistently affects performance but often goes unnoticed is coaxial cable power loss—measured in dB per meter. Whether you’re deploying a wireless bridge, running signal to a rooftop antenna, or building a low-power IoT network, understanding how signal attenuation works is key to ensuring consistent results.
In this article, we’ll explore how power loss occurs, compare attenuation values across cable types, and help you choose the best coax cable for your frequency and application.
Why Coaxial Cable Power Loss Matters
Coaxial cables act as conduits for RF energy, but they aren’t perfect. As signal travels through the conductor and dielectric, it encounters resistance and dielectric losses—especially at high frequencies.
Common Symptoms of Excessive Loss:
- Reduced signal range
- Poor SNR (Signal-to-Noise Ratio)
- Failure to meet link budget in long-distance deployments
Even with high-gain antennas and powerful transmitters, a poorly chosen coax cable can degrade performance drastically.
Understanding Attenuation Per Meter: The Basics
Attenuation refers to the amount of signal loss over a given distance, usually expressed as dB/meter. It increases with:
- Frequency (loss is worse at higher frequencies)
- Length (longer runs = more loss)
- Cable type (material, shielding, diameter)
Here’s a simplified formula:
Total Loss (dB) = Loss per meter (dB/m) × Cable length (m)
Attenuation Table – Popular Coax Types at Common Frequencies
| Cable Type | 100 MHz | 500 MHz | 900 MHz | 2.4 GHz | 5.8 GHz |
|---|---|---|---|---|---|
| RG58 | 0.18 | 0.48 | 0.66 | 1.25 | 2.20 |
| RG6 | 0.15 | 0.30 | 0.42 | 0.85 | 1.75 |
| LMR200 | 0.10 | 0.28 | 0.40 | 0.75 | 1.45 |
| LMR400 | 0.06 | 0.15 | 0.21 | 0.38 | 0.70 |
| RG213 | 0.10 | 0.25 | 0.36 | 0.70 | 1.30 |
Data based on typical manufacturer specs. For precision, consult datasheets.
How to Calculate Total Signal Loss in Your Setup
Let’s say you’re running 25 meters of RG58 to a rooftop antenna transmitting at 2.4 GHz:
Loss = 1.25 dB/m × 25m = 31.25 dB
That’s a huge loss—enough to render your transmission unusable.
Now try LMR400:
Loss = 0.38 dB/m × 25m = 9.5 dB
Always factor in total cable length and frequency. For runs over 10m at >1GHz, choose low-loss cable.
Choosing the Right Cable for Your Application
< 5 Meters
- Recommended: RG58, RG174 (for budget or compact setups)
- Use in indoor patch cables, short device interconnects
5–30 Meters
- Recommended: RG6, LMR200
- Suitable for medium-distance links in Wi-Fi, DVB, or LTE systems
30+ Meters or Outdoor
- Recommended: LMR400, RG213
- Outdoor-rated, UV-resistant jackets, double shielding
- Use in rooftop antennas, base stations, surveillance
Match impedance (50Ω or 75Ω) to equipment. Always use quality connectors.
Real-World Use Cases
Case 1: Wireless Bridge
- 40m LMR400 for 5.8GHz link
- Low-loss critical to maintaining throughput over long range
Case 2: LoRa Node on Factory Roof
- 20m RG6 from gateway to roof-mounted antenna
- Balanced performance and cost
Case 3: SDR Receiver Setup
- Short 2m RG58 connection indoors
- Minimal concern for loss; low cost preferred
Bafitop’s Coaxial Cable Solutions
| Model | Impedance | Shield Type | Frequency Range | Application |
|---|---|---|---|---|
| BFT-LMR400 | 50Ω | Quad | 0–6GHz | Long-run outdoor |
| BFT-RG58-DS | 50Ω | Dual | 0–1GHz | Short-run devices |
| BFT-RG6-PRO | 75Ω | Foil+Braid | 0–2.5GHz | Video, TV, IoT |
| Custom OEM | 50/75Ω | As needed | As needed | Project-based |
FAQ: Coax Loss Questions
Q1: Is attenuation linear with length?
Yes—double the cable length, double the dB loss.
Q2: Does coiling affect power loss?
No, unless bending radius is too tight and affects the shield.
Q3: Can I use RG6 for 2.4GHz Wi-Fi?
Yes, but with increased loss. Consider LMR200/LMR400 for longer runs.
Q4: What’s the lowest-loss coax cable?
LMR400 or better (like Bafitop LMR400). Large diameter, high shielding.
Q5: Can I mix 50Ω and 75Ω cables?
Not recommended—impedance mismatch leads to reflections.
Contact Bafitop for RF Cable Consultation
Whether you’re engineering a wireless system or evaluating your cable loss budget, we’re here to help.
📧 Email: sales@bafitop.com
📞 Phone: 86-15817341810
🌐 Website: www.bafitop.com
Get samples, request OEM specs, or speak to our RF team today.
