jabidof said:
Hello!
There exists many antennas that differs in their radiating resistance. But can we say that a 50 ohms p@tch antenna is less sensitive to e.g. the hand than a 300 ohms folded dipole antenna?
To enlarge the issue, what antenna characteristic (-10dB bandwidth, environment sensitivity, etc.) is affected by a low resp. a high radiating resistance value?
Thanks for your inputs.
BR
Generally speaking, the antenna's connector impedence, and radiation rasistance may be different.
Radiation resistance is a model, the power dissipate into the radiating resistance is the power sent into the space.
Of course not all power sent to a TX antenna is radiated, a little will be reflected (VSWR) and little will heat the antenna.
In VHF, UHF and Microwave internal loss are negligible.
After this preface, i'll try to answer.
The term "sensitivity" don't apply to antennas.
Antennas are identified by:
-Directivity (the thickness of the beam)
-Freedom from sidelobes
-Cross-polar performances
-VSWR
Often the Gain may be found instead Directivity.
Higher Gain means thinner beam !
Gain is mainly related to aperture Area and λ.
The importance of the input impedence is only related to power reflection consideration. You should minimize the reflection coefficient!
So 50 Ω antennas connected to 50Ω generators and 300Ω dipole connected to 300Ω generators.
The impedence itself don't influence the Gain