A reader referred me to a video of a presentation to a radio club, the subject being “The Truth About Magnetic Loop Antennas – MYTH BUSTING!”
The presentation includes prediction and measurement of a small transmitting loop. This article tries to reconcile the claimed radiation efficiency between prediction and measurement.
Radiation Efficiency
The presentation liberally uses the term “efficiency”, let us take that to mean Radiation Efficiency:
the ratio of the total power radiated by an antenna to the net power accepted by the antenna from the connected transmitter.
Note that Radiation Sphere requires that radiated power must be measured / determined / summed in the far field.
Radiation fields decay inversely proportional to distance, other fields immediately around an antenna decay more quickly and are insignificant for the purpose of radio communications at great distances. Hence, Radiation is the usual objective of radio communications antennas.
The calculation tool used in the presentation defines:
Efficiency (%): The percentage of input energy that is actually radiated and not lost as heat.
The prototype loop antenna
The prototype loop antenna is described:
A table is given which appears to be predicted performance based on https://miguelvaca.github.io/vk3cpu/magloop.html . Continue reading Review of “The Truth About Magnetic Loop Antennas – MYTH BUSTING!”