EIRP (Effective Radiated Power)
Calculate the equivalent isotropically radiated power (EIRP), EIRP = P_tx + G − L, adding the transmitter power P_tx (dBm) to the antenna gain G (dBi) and subtracting cable and connector losses L (dB). The result, in dBm, is the power a theoretical isotropic antenna would need to radiate to produce the same power density in the direction of the real antenna's maximum gain. It is the quantity regulated by telecom authorities (legal EIRP limits) and the transmit-side starting point of a link budget. Enter the transmitter power, the antenna gain and the losses.
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EIRP (potência irradiada efetiva)
A EIRP (potência isotrópica irradiada equivalente) responde: na direção em que minha antena aponta, qual a potência efetiva que estou irradiando? Ela combina os três fatores do lado transmissor num cálculo em decibéis: EIRP = P_tx + G − L, somando a potência do transmissor P_tx (dBm) ao ganho da antena G (dBi) e subtraindo as perdas de cabos, conectores e divisores L (dB). O resultado, em dBm, equivale à potência que uma antena isotrópica teórica (que irradia igualmente em todas as direções) precisaria emitir para igualar a densidade de potência que a antena real, com seu ganho, produz na direção de máximo. A EIRP é importante por dois motivos. Primeiro, é o ponto de partida do cálculo de enlace: dela se subtraem as perdas de propagação para achar o sinal no receptor. Segundo, é a grandeza regulamentada: as agências de telecomunicações (Anatel, FCC) limitam a EIRP máxima permitida em cada faixa — por isso aumentar o ganho da antena obriga a reduzir a potência do transmissor para não ultrapassar o limite legal. Informe a potência do transmissor, o ganho da antena e as perdas.
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Calculate the fade margin, M = P_rx − S, subtracting the receiver sensitivity S (dBm) from the received power P_rx (dBm). The result, in dB, is the slack between the arriving signal and the minimum the receiver can demodulate — the reserve available to absorb temporary fades caused by rain, multipath, vegetation and atmospheric variations. Reliable links typically require margins of 10 to 30 dB, depending on the desired availability and environment. It is the final check of a radio link budget. Enter the received power and the receiver sensitivity.
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Calculate the link budget of a radio link in dB by adding transmit power and gains, then subtracting path losses. Useful for radio communication projects.
Free Space Path Loss (FSPL)
Calculate the free space path loss (FSPL), L = 20·log₁₀(d) + 20·log₁₀(f) + 32.44, from the distance d (km) and the frequency f (MHz). The result, in dB, is the attenuation a radio signal suffers simply by spreading through space, with no obstacles — proportional to the square of distance and frequency. It is the central term of any link budget: the greater the distance or frequency, the higher the loss and thus the more power or antenna gain needed. The 32.44 constant applies for km and MHz. Enter the distance and the frequency.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.