When to use: Use to calculate total coaxial cable attenuation for DAS trunk lines, BDA donor/server cable runs, antenna feed lines, and any RF distribution system. Attenuation increases with frequency and length — a critical factor in passive DAS design. Includes connector loss. Use the result as cable loss input in the Link Budget and EIRP calculators. For DAS trunk lines, LMR-400 or 1/2" Heliax is standard practice.
The Coaxial Cable Loss Calculator computes total RF signal attenuation for common cable types across frequencies from 150 MHz to 5.8 GHz, including connector losses, making it the essential tool for DAS trunk line design, BDA feed cable budgeting, and antenna system link budgets. Engineers use it to select the right cable type and size cable runs to maintain adequate signal levels at every antenna port.
Coaxial cable attenuation increases with both frequency and cable length. Total cable loss (dB) = (Attenuation rate in dB/100 ft) × (Length in ft / 100). Each connector adds 0.1 to 0.5 dB of insertion loss depending on type and quality of installation — poorly crimped or weathered connectors can add significantly more. Total insertion loss = cable loss + (number of connectors × connector loss per connector).
Attenuation rates vary substantially by cable type: RG-58 thin coax attenuates at 10.5 dB/100 ft at 800 MHz, while 7/8-inch Heliax (LDF5-50A) attenuates at only 0.88 dB/100 ft — a factor of 12 difference. Cable loss is not linear with frequency; it scales approximately as the square root of frequency due to the skin effect in the center conductor and shield.
NFPA 1221 and IFC 510 do not mandate specific cable types, but they require the completed system to meet minimum RSSI levels at every test point. TIA-568 Series standards govern coaxial cable specifications for structured cabling systems. The Andrew/CommScope LDF and FSJ series Heliax cables comply with MIL-C-17 military specifications. For public safety BDA systems, cable selections must be included in the engineer-stamped design package submitted for AHJ review per IFC 510.5.2.
LMR-400 (2.23 dB/100 ft at 800 MHz) is the industry standard for passive DAS trunk lines up to 150 ft. For runs exceeding 150 ft, upgrade to 1/2-inch Heliax (1.83 dB/100 ft) or 7/8-inch Heliax (0.88 dB/100 ft) to keep trunk line loss under 3 dB. Every decibel of cable loss directly reduces the signal available at the antenna port and therefore reduces coverage radius. Connector quality matters: use proper crimp tools for LMR series cables and silver-plated N-type connectors for frequencies above 2 GHz. For outdoor runs, use weatherproof connectors and UV-resistant jacket cables rated for direct burial or conduit installation.
Select the cable type from the dropdown — the table includes the most common 50-ohm and 75-ohm coaxial cables used in RF systems. Select the operating frequency band that matches your radio system (800 MHz for P25, 1900 MHz for LTE, etc.). Enter the total cable length in feet and the number of connectors in the run. Adjust the connector loss per connector (0.3 dB for high-quality N-type, 0.5 dB for SMA or average PL-259). The result is the total insertion loss in dB, which feeds directly into the EIRP and Link Budget calculators.
For a 200-foot run at 800 MHz, LMR-400 would contribute 4.46 dB of cable loss, which may be acceptable. For tighter loss budgets, use 1/2-inch Heliax (FSJ4-50B) at 3.66 dB for 200 ft, or 7/8-inch Heliax (LDF5-50A) at 1.76 dB. The choice depends on your available EIRP headroom after accounting for splitter loss and required antenna port level.
50-ohm cable (LMR, Heliax, RG-213, RG-8) is standard for RF transmitting and receiving systems. 75-ohm cable (RG-6, RG-11) is used for CATV and video distribution. Connecting 50-ohm and 75-ohm systems without an impedance transformer causes a VSWR of 1.5:1 and a reflected power of 4%, which is usually unacceptable in a calibrated system.
Total cable loss (trunk + distribution + connectors) is subtracted from the BDA output power to determine the signal level at the antenna port. This value, plus antenna gain, gives the EIRP at the antenna. Cable loss on the receive side (from antenna to BDA input) reduces the effective donor RSSI that the BDA sees, limiting the available gain margin.
Yes. Cable attenuation increases approximately 0.1% per degree Celsius above 20°C due to increased conductor resistivity. For rooftop or outdoor runs in hot climates, add a 0.5–1 dB margin to the calculated loss to account for worst-case summer temperatures. Cold temperatures below −20°C can also make the cable jacket brittle and crack the dielectric.
RG-58 is acceptable only for very short runs (under 20 ft at 800 MHz) due to its high attenuation rate of 10.5 dB/100 ft. For any cable run that is part of a public safety in-building system design, minimum LMR-240 or preferably LMR-400 is recommended to maintain an acceptable link budget.
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