In our real world all the Radio Communications happen through antenna. The antenna characteristics are very important to the success of any radio based system. Antenna helps us either to radiate or receive. Antennas are called transducers because convert voltage to a radio signal during transmission and radio signal to voltage during reception. It is basically the electromagnetic waves that are radiated or absorbed. While this is all one side of it, at the other side, having the proper antenna size is the critical factor. The antenna follows Quarter Wavelength or λ/4 for the length.
The relation between wavelength and frequency is given by C = F*λ
Antenna is nothing but a simple conductor. One important point here is when this connector absorbs electromagnetic radiation as a part of signal reception, it induces current. While this is essential for the operation of the antenna, it is not essential for the other connectors to get the current induced. We can take an example of the cables which are connectors or a Mechanical enclosure or a trace on a circuit board which are all connectors and there is a chance of radiation induced into them. These are all susceptible which causes EMI/EMC radiation. This is what is tested in the RF immunity tests during the EMI/EMC tests to see if our PCB along with cables are immune or not. Luckily, all these doesn't match the Quarter Wavelength or λ/4 which we have talked for antenna. It is important the length of such should not exceed λ/10. Even if they match λ/4 sufficient shielding need to be provided for the system. Take for example the case of cables that are shielded.
While Antennas are needed to absorb the radiation, these all external equipment, cables, boards should absorb any energy for proper operation.
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