- #1
kevinisfrom
- 36
- 0
- TL;DR Summary
- Limits of Friis Transmission Equation
If we had a transmitter antenna with 40dBi gain, and the same antenna on the receiving end, based on reciprocity, the receiver antenna would be 40dBi too. Assuming a wavelength of 0.1m and transmitted power of 100W over 100m, the received power comes out to be 63W based on this calculator here: https://www.everythingrf.com/rf-calculators/friis-transmission-calculator
Does the Friis equation take into account beam efficiency? That is, the power transmitted in main beam vs the total power transmitted (thus losses from sidelobes)? I doesn't seem like antenna gain tells us how much power was lost from the non-primary beam. For example, if the distance was decreased to 10m, the power received will go to 6kW, which cannot be possible. I guess more broadly, what are the limits properly using the Friis Transmission Equation?
Does the Friis equation take into account beam efficiency? That is, the power transmitted in main beam vs the total power transmitted (thus losses from sidelobes)? I doesn't seem like antenna gain tells us how much power was lost from the non-primary beam. For example, if the distance was decreased to 10m, the power received will go to 6kW, which cannot be possible. I guess more broadly, what are the limits properly using the Friis Transmission Equation?
Last edited: