This tool is designed to calculate the power at the receiver using link budget analysis.
Output
Overview
A link budget is created if all the gains and losses from the transmitter, through the medium - free space, cable, waveguide, or fiber - to the receiver in a telecommunication system are accounted. The parameters included in the link budget include the signal attenuation, feedline as well as miscellaneous losses. Fading is also considered through an additional margin whose magnitude depends on its anticipated severity. Mitigating techniques such as antenna diversity or frequency hopping can be used to reduce the amount of margin.
This calculator is designed to calculate the received power at the receiver by factoring in all the losses and gains that an RF signal may encounter.
Equation
$$P_{out} = P_{t} + G_{t} - L_{t} - L_{fs} - L_{m} + G_{r} - L_{r}$$
Where:
$$P_{out}$$ = power at the received in dBm
$$P_{t}$$ = power at the transmitter in dBm
$$G_{t}, G_{r}$$ = gains of the transmit and receive antennas respectively
$$L_{t}, L_{r}$$ = losses at the transmit and receive circuits respectively
$$L_{fs}$$ = free space path loss = $$20log_{10}d + 20log_{10}f + 32.44$$
Applications
An area where link budgets are extremely important are communication systems requiring precise calculations. One example is in Earth-Moon-Earth communications where the signal powers involved are often very low. This is due to the moon having a very low albedo (reflectivity) and the high path loss over the 770,000 km return distance. Through link budget calculations, the correct antenna parameters are determined. It is common to use transmit antennas higher than 100 W with a gain of more than 20 dB in Earth-Moon-Earth communications.
Another example is during NASA's Voyager Program which remains to have the highest known path loss and lowest link budgets in any telecommunication circuit. It is said that the received signal is a billion times weaker than a wristwatch even after being processed by the Deep Space Network.
Further Reading
Textbook - Principles of Radio
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