Free RF calculator
Coax cable loss calculator
Matched-line loss for a feedline run, from the cable, the frequency and the length, with the connector losses on top, and how much of the power actually reaches the far end.
Matched-line loss at room temperature. Installed loss runs higher with VSWR, heat, age and moisture, so treat this as a planning figure and add margin.
Runs in your browser; nothing you enter is sent anywhere. The same math the Sentinel RF product uses, tested against it. A planning figure, not an engineering sign-off.
The math
Attenuation follows the form cable datasheets publish:
A (dB per 100 ft) = k1 x sqrt(f) + k2 x f f in MHz
k1 carries the conductor loss, which grows with the square root of frequency; k2 carries the dielectric loss, which grows with frequency itself. Each cable's constants come from the published datasheet of one common cable of that size and construction. Your cable's own datasheet is the authority.
Reading the result
3 dB of loss is half the power and 10 dB is a tenth. The same dB costs you in both directions: on transmit it comes off the ERP, and on receive, loss ahead of the first amplifier adds to the system noise figure dB for dB.
This is matched-line loss at room temperature. An installed run loses more with VSWR, heat, age and moisture, so carry margin.
In Sentinel RF
In the product the same cable model feeds the ERP, link budget and talk-in calculations directly, and its cable list carries the exact datasheet part for each row.
Other free calculators
- Intermod calculatorThird and fifth order products for a site's transmitters, and which ones land on a receiver.
- ERP and EIRP calculatorERP from power, gain and line loss, or the TX power a licensed ERP allows.
- Fresnel zone calculatorZone radius, 60% clearance and earth bulge at a point on the path, plus knife-edge loss.
- Near-field and far-field calculatorWhere the reactive near field ends and the far field begins, and which one a point is in.
Forty-five calculators, and the FCC data behind them.
The product runs these against real licenses, real towers and real terrain, and prints the result under your operation's name.