The formula
Total loss = α(f) × (L / 100) + Cc, where α(f) is the cable attenuation in dB per 100 m at your frequency, L is the run length in metres, and Cc is the summed connector/crimp loss.
How to calculate the loss of your cable run
- Select the exact cable family and enter the operating frequency. Standard LMR, flexible variants and 75 Ω versions are not interchangeable specifications.
- Enter the installed length and check its unit. For a datasheet quoted in dB/100 ft, multiply that attenuation by 3.2808 to obtain dB/100 m before using manual entry.
- Add the total loss of connectors and adapters separately; do not add it again if your measured assembly loss already includes them.
- Check the source, frequency limit and extrapolation warning. Use a manufacturer measurement for your assembly when accuracy matters.
For example, the LMR-400 table gives 35.5 dB/100 m at 5800 MHz. A 30 m run therefore loses 10.65 dB before connectors. Add 0.5 dB of total connector loss to obtain 11.15 dB. To include both transmit and receive feeders, continue in the RF link budget calculator.
Why attenuation depends on frequency
Cable loss rises with frequency because conductor loss grows roughly with √f (skin effect) while dielectric loss grows roughly with f. Manufacturer tables therefore quote α at several frequencies; this tool interpolates between those points on a log-frequency axis and flags any result that falls outside the published range as extrapolated.
Times Microwave LMR and generic RG references
LMR entries use Times Microwave's standard cable datasheets. Their 3000 MHz points are interpolated on log frequency between the published 2500 and 5800 MHz values. LMR-240 uses the conservative 6 GHz cable-product limit; LMR-400 and LMR-600 product pages specify 8 GHz. All three attenuation tables here end at 5800 MHz.
The updated RG entries use named Belden reference parts, with dB/100 ft multiplied by 3.2808. They remain typical estimates for generic RG types. RG-58/U and RG-58A/U intentionally share the 8240 reference; RG-213/U and RG-214/U share the 8267 reference. These proxies do not imply identical construction or shielding. Values between published frequencies use the calculator's existing interpolation.
| Cable | 900 MHz | 2000 MHz | Source |
|---|---|---|---|
| LMR-240 (50Ω, 6.10 mm) | 24.80 | 37.70 | Times Microwave LMR-240 datasheet |
| LMR-400 (50Ω, 10.3 mm) | 12.80 | 19.60 | Times Microwave LMR-400 datasheet |
| LMR-600 (50Ω, 14.99 mm) | 8.20 | 12.80 | Times Microwave LMR-600 datasheet |
| RG-316 (50Ω, 2.5 mm, PTFE) | 89.57 | 139.43 | Belden 83284 datasheet |
| RG-58/U (50Ω, 4.95 mm) | 44.95 | Outside table | Belden 8240 datasheet |
| RG-58A/U (50Ω) | 44.95 | Outside table | Belden 8240 datasheet (RG-58 proxy) |
| RG-213/U (50Ω, 10.3 mm) | 24.93 | 48.39 | Belden 8267 datasheet |
| RG-214/U (50Ω, 10.3 mm) | 24.93 | 48.39 | Belden 8267 datasheet (RG-213 proxy) |
| RG-6/U (75Ω, 6.9 mm) | 19.59 | 30.18 | Belden 1694A datasheet |
Belden 8240 stops at 1000 MHz, 83284 at 3000 MHz, 8267 at 4000 MHz and 1694A at 6000 MHz. The 8267 reference has a wide gap from 1000 to 4000 MHz; intermediate estimates need checking against your exact cable. The calculator flags results beyond each table as extrapolated.
Gigatronix LBC — verified datasheet data
The Gigatronix LBC low-loss family is included with attenuation transcribed directly from the official datasheets (status verified). Representative figures (dB / 100 m):
| Type | Jacket Ø | 900 MHz | 1800 MHz | 2500 MHz | Rated max |
|---|---|---|---|---|---|
| LBC100 | 2.79 mm | 74.90 | 109.00 | 130.60 | 6 GHz |
| LBC195 | 4.95 mm | 36.50 | 52.50 | 62.40 | 11 GHz |
| LBC240 | 6.10 mm | 24.80 | 35.60 | 42.40 | 11 GHz |
| LBC400LSZH | 10.29 mm | 12.80 | 18.60 | 22.20 | 11 GHz |
| LBC600 | 14.99 mm | 8.20 | 12.14 | 14.44 | 6 GHz |
Sources: Gigatronix LBC100 Rev. 110218.4, LBC195 Rev. 110214.5, LBC240 Rev. 110218.4, LBC400LSZH Rev. 111110.4, LBC600 Rev. 120201.3. All 50 Ω. LBC400LSZH has a Low-Smoke Zero-Halogen, UV-rated (UL1581:1200) jacket.
Worked example
Gigatronix LBC240, 10 m, 2.4 GHz: interpolating the verified table between 2000 MHz (37.70 dB/100 m) and 2500 MHz (42.40 dB/100 m) gives ≈ 41.54 dB/100 m, so 10 m ≈ 4.15 dB. For an in-range comparison at 900 MHz, 10 m of LMR-400 loses 1.28 dB, while the Belden 8240 reference used for RG-58/U loses about 4.49 dB. The RG-58 reference ends at 1000 MHz; a 2.4 GHz result is extrapolated and needs an exact cable datasheet.