Hi Raphael,
Can you confirm the following statements, in order to improve my understanding of some basic concepts.
I assume that by efficiency you mean radiation efficiency (ratio of the radiated power to the input power of the antenna) and that no other definition is being used.
The Radiation resistance does not change between a tuned and un-tuned loop of the same dimensions and construction.
The radiation resistance is given by
R rad.= 31200 x (NxA / wavelength of interest^2) ^2
N ¨C number of turns, A=pi x ( D/2)^2 ,where D is diameter of loop.
Increasing the number of turns on a loop will increase its Radiation Resistance, but this will be offset by increased losses.
The difference in radiation efficiency between a tuned and untuned loop, is simply due to mismatch losses, as all other losses must remain the same between the same.
Radiation efficiency would be the same as the total antenna efficiency if there was no loss due to impedance mismatch.
If a narrow band matching network is added to an untuned antenna, in order to minimise mismatch losses at a specific frequency (effectively becoming a tuned antenna), the radiation efficiency is improved.
The Q factor (and therefore bandwidth) of the matched antenna is an indicator of the radiation efficiency.
This older thread my be of relevance regarding Antenna Factor.
/g/loopantennas/topic/70230511Specifically the link to
Regards,
Martin
