Point-to-Point Link Calculator
Close a point-to-point wireless link: free-space path loss, received signal level, EIRP and the fade margin left over.
Inputs
Fade Margin
26.7dB
Free-Space Path Loss
129.29dB
Received Signal Level
-58.29dBm
Effective Isotropic Radiated Power
48.5dBm
Link Assessment
Carrier-grade — the link will ride out heavy weather
Step by step
Values used
Link distance = 12 km; Frequency = 5,800 MHz; Transmit power = 23 dBm; Transmit antenna gain = 27 dBi; Receive antenna gain = 27 dBi; Cable and connector loss per end = 1.50 dB; Rain, foliage and misc losses = 3 dB; Receiver sensitivity = -85 dBm
Point-to-Point Link
FSPL = 20·log10(d_km) + 20·log10(f_MHz) + 32.44; received level = Tx power + antenna gains − cable losses − FSPL − misc losses; fade margin = received level − sensitivity.
Regulatory EIRP
EIRP = transmit power + antenna gain − cable loss, which is the figure regulators cap.
Fade Margin
= 26.7 dB
Free-Space Path Loss
= 129.29 dB
Received Signal Level
= -58.29 dBm
Effective Isotropic Radiated Power
= 48.5 dBm
Link Assessment
= Carrier-grade — the link will ride out heavy weather
How it works
Free-space path loss grows 6 dB for every doubling of distance and 6 dB for every doubling of frequency. Adding transmitter power and antenna gain, then subtracting every loss along the path, gives the level arriving at the receiver; the difference from its sensitivity is the fade margin. A link that closes with 3 dB of margin works on the day you commission it and drops during the first heavy rain, so margin — not raw signal level — is the number that decides whether the hop is production-ready.
Formulas
Point-to-Point Link
FSPL = 20·log10(d_km) + 20·log10(f_MHz) + 32.44; received level = Tx power + antenna gains − cable losses − FSPL − misc losses; fade margin = received level − sensitivity.
- fspl
- Loss from spreading alone, before any obstruction
- fadeMargin
- Decibels of signal you can lose before the link drops
Regulatory EIRP
EIRP = transmit power + antenna gain − cable loss, which is the figure regulators cap.
Frequently Asked Questions
How is Point-to-Point Link calculated?
FSPL = 20·log10(d_km) + 20·log10(f_MHz) + 32.44; received level = Tx power + antenna gains − cable losses − FSPL − misc losses; fade margin = received level − sensitivity. Free-space path loss grows 6 dB for every doubling of distance and 6 dB for every doubling of frequency. Adding transmitter power and antenna gain, then subtracting every loss along the path, gives the level arriving at the receiver; the difference from its sensitivity is the fade margin.
Why does Point-to-Point Link matter?
A link that closes with 3 dB of margin works on the day you commission it and drops during the first heavy rain, so margin — not raw signal level — is the number that decides whether the hop is production-ready.
What values do I need to enter?
This calculator takes 8 inputs: Link distance, Frequency, Transmit power, Transmit antenna gain, Receive antenna gain, Cable and connector loss per end, Rain, foliage and misc losses, Receiver sensitivity. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.