Microwave Link Calculator

Path clearance, fade margin, and availability.

TX power (dBm)

TX antenna gain (dBi)

RX antenna gain (dBi)

Frequency (GHz)

Link distance (km)

RX threshold (dBm)

Misc. losses (dB)

Climate factor

Tab to move between fields

Fade margin (dB)

21.92

Received signal (dBm)-48.08

Availability (%)99.9

Annual outage (min)513.06

Free-space path loss (dB)141.08

System gain (dB)163

1st Fresnel zone radius (m)7.91

Rain attenuation (dB)295.94

How to Use This Calculator

Enter the operating frequency in GHz and the link distance in km.
Input the transmit power in dBm, the TX and RX antenna gains in dBi, and the receiver sensitivity threshold in dBm.
Set the misc. losses (waveguide, connectors, radome) in dB and choose a climate factor for your region (0.25 dry/mountain, 1.0 average, 4.0 hot humid coast).
Review the Free Space Path Loss, System Gain, Fade Margin, and Link Availability percentage, along with estimated annual outage minutes, Fresnel zone radius, and rain attenuation.
Target a fade margin of at least 25-40 dB for 99.99%+ link availability.

How the result changes with RX threshold (dBm)

TX power (dBm): Transmitter output power in dBm. Typical: 15-25 dBm for licensed microwave.
TX antenna gain (dBi): Transmit antenna gain. 0.6m dish ~33 dBi, 1.2m ~38 dBi at 18 GHz.
RX antenna gain (dBi): Receive antenna gain. Usually matches TX antenna.
Frequency (GHz): Operating frequency. Common bands: 6, 11, 18, 23, 38, 60, 80 GHz.
Link distance (km): Point-to-point distance between towers in kilometers.
RX threshold (dBm): Receiver sensitivity threshold at target BER (e.g., 10⁻⁶). Typical: -65 to -80 dBm.
Misc. losses (dB): Waveguide/coax losses, connectors, radome, branching. Typical: 2-5 dB.
Climate factor: Vigants C-factor: 0.25 (dry/mountain), 1.0 (average), 4.0 (hot humid coast).

Fade margin (dB): Signal headroom above receiver threshold. Target: 25-40 dB for 99.99%+ availability.
Received signal (dBm): Calculated received power level under clear-sky conditions.
Availability (%): Link availability using Vigants-Barnett multipath model (no diversity).
Annual outage (min): Estimated multipath outage minutes per year.
Free-space path loss (dB): Theoretical loss in free space at the given frequency and distance.
System gain (dB): Total system gain: TX power + antenna gains - losses - RX threshold.
1st Fresnel zone radius (m): First Fresnel zone radius at midpoint. Ensure 60%+ clearance above obstacles.
Rain attenuation (dB): Estimated path attenuation during moderate (25 mm/hr) rainfall.

Identify Input Parameters
4 parameters
TX power (dBm) = 20, TX antenna gain (dBi) = 38, RX antenna gain (dBi) = 38, Frequency (GHz) = 18 = 8 input(s) provided
Calculate Fade margin
Fade margin = rxLevelDbm - rxThresholdDbm
21.92 = 21.92
Calculate Received signal
Received signal = txPowerDbm + txAntennaGainDbi + rxAntennaGainDbi - fsplDb - miscLossesDb
-48.08 = -48.08
Calculate Availability
Availability
99.9025 = 99.9025