RF Coax Cable Loss Calculator
Estimate total attenuation (dB), power delivered, and output power based on cable type, frequency, length, and connector losses.
Preset values are approximate and vary by manufacturer, temperature, cable age, installation quality, VSWR, and moisture.
Why an RF cable attenuation calculator matters
When people troubleshoot weak signal performance, they often focus on radios and antennas first. But coaxial cable loss can quietly eat a large part of your transmit power and reduce received signal strength. A good RF cable attenuation calculator helps you estimate this loss before you install a cable run.
This page is designed as a practical coax cable loss calculator for ham radio, Wi-Fi backhaul, ISM systems, LoRa, cellular boosters, scanner setups, SDR stations, and lab work. If you know cable type, frequency, length, and connector count, you can get a fast, useful estimate.
How the calculator works
The tool uses a simple frequency-scaling model based on a reference attenuation value:
- RefAtten is attenuation in dB per 100 ft at the reference frequency.
- f is your operating frequency (converted internally to MHz).
- n is frequency exponent (typically around 0.5 to 0.7 for many practical cables).
Then total loss is computed as:
And power transfer ratio is:
Quick interpretation of dB results
- 1 dB loss ≈ about 79% power delivered.
- 3 dB loss ≈ about 50% power delivered.
- 6 dB loss ≈ about 25% power delivered.
- 10 dB loss ≈ about 10% power delivered.
If your run is long and high-frequency, upgrading cable can produce dramatic gains without touching your radio.
Typical use cases
1) 900 MHz and 2.4 GHz systems
At UHF and microwave frequencies, attenuation climbs quickly. Long runs of small cable can ruin link budget. Use low-loss cable and keep feedline short when possible.
2) Base station upgrades
If you are moving from RG-58 to LMR-400, this calculator helps estimate how much TX/RX improvement you can expect from cable replacement alone.
3) Site planning and budgeting
Before purchasing hardware, compare several cable types and lengths. This is often the fastest way to identify a cost-effective improvement.
Example cable comparison at higher frequency
The exact values vary, but the trend is consistent: larger, lower-loss cable matters more as frequency and length increase.
| Cable Type | Approx Ref (dB/100 ft @ 100 MHz) | Best For |
|---|---|---|
| RG-174 | 7.2 | Very short patch leads |
| RG-58 | 4.9 | Short, lightweight runs |
| RG-213 | 3.1 | General-purpose HF/VHF/UHF |
| LMR-240 | 2.8 | Moderate loss, flexible installations |
| LMR-400 | 1.5 | Low-loss fixed station runs |
| LMR-600 | 1.0 | Very low loss, longer fixed runs |
Tips to reduce RF feedline loss
- Keep cable runs as short as practical.
- Choose cable with lower dB/100 ft at your operating frequency.
- Minimize adapters, barrel connectors, and unnecessary jumpers.
- Use high-quality connectors and proper crimp/solder technique.
- Seal outdoor connectors to prevent moisture ingress.
- Avoid sharp bends and crushing; mechanical damage increases loss.
FAQ
Is this calculator exact?
No. It is a strong engineering estimate. Manufacturer datasheets measured at specific frequencies are the best source for final design.
Why does attenuation increase with frequency?
Skin effect and dielectric losses rise as frequency rises, so high-frequency operation suffers more feedline loss.
Does connector quality really matter?
Yes. Poor connectors can add measurable insertion loss and reflections, especially above a few hundred MHz.
Can I use meters and GHz?
Yes. This tool supports meters/feet and kHz/MHz/GHz and converts internally.
Final thoughts
An RF cable attenuation calculator is one of the simplest ways to improve link performance before spending money on radios or antennas. Even modest reductions in feedline loss can significantly improve both transmit efficiency and receive sensitivity. Use this calculator early in your design process, then verify with cable datasheets and real-world measurements where possible.