Link Budget Calculator

A link budget is the complete dB ledger of a radio link: every gain the signal picks up and every loss it suffers between the transmitter's power amplifier and the receiver's detector, totalled against the level the receiver needs. Because everything is in dB and dBm, the whole budget is one line of addition: P_rx = P_tx + G_tx − L_tx + G_rx − L_rx − L_path − L_misc.

Two derived quantities matter most. EIRP — effective isotropic radiated power — is the level at the start of the path (transmit power plus antenna gain minus feed loss), the number regulators limit and datasheets quote. Link margin is the final verdict: received power minus receiver sensitivity. Positive margin means the link closes; the size of the margin is the reserve against everything the budget didn't model — fading, aging, rain, misalignment. Terrestrial links typically carry 10–20 dB of fade margin; satellite links are engineered to run much thinner.

Enter the path loss from whatever propagation model fits the link — the free-space path loss calculator provides the best-case value — and enter all losses as positive numbers; the calculator applies the signs. The waterfall chart shows the running level after each term, which makes it easy to see which single term dominates the budget and where a dB of improvement buys the most.