Resonant and NonResonant Antenna
Question 1. If we need to find out the length of antenna needed for the frequency 2.4 GHz. How we find out length.
Since antenna is resonating type. We always find wavelength first.
lambda= Speed of light / Frequency
so for 2.4 GHz lambda=3 X 10^8/ 2.4 X 10 ^9 m
so we decide our antenna to have length lambda/2. So this antenna resonates at 2.4 GHz but if frequency other then 2.4GHz falls on this type of antenna, it will behave merely like a piece of metal.
So resonating antennas are antenna having length in terms of wavelength.
Question 2. Since ionosphere reflects back the signal so frequency needs to change, Then how a single antenna can be used to receive multiple frequencies if it is resonant antenna since it will work for single frequency as described above.
Non resonant type of antenna is used. In non-resonant type of antenna the length is not deciding factor for the frequency for which my antenna works. It is also called traveling wave type of antenna. While resonant antenna is dependent on standing waves produced. The difference between Standing wave and traveling wave antenna will be discussed in next article.
So two things to keep in mind, Resonant antenna length is dependent on frequency and always defined in terms of wavelength. while resonant type of antenna are traveling wave antenna for which frequency of operation is independent of length.
