Selecting an antenna for testing can sometimes be straightforward but often requires some specific consideration.
Not all antennas are created equal, and when it comes to frequency different antenna styles perform better at some frequencies and not at others. Some special considerations are sometimes required in antenna design typically at very high and very low frequencies.
Low frequency radio signals tend to act more like low frequency audio, traveling through and around objects in non-directional ways. On the other hand, elements for high frequency antennas on the order of GHz can be very small, but signals tend to propagate in very directional ways more like light, but also won’t go around or through objects. Because of this, low frequency signals are naturally more omnidirectional and high frequency ones are more directional. Attempting to make directional low frequency antennas or omnidirectional high frequency ones can be challenging.
Other antenna design factors such as bandwidth are frequency-dependent as well. High frequencies require more precise length elements, making it more difficult to construct a wide bandwidth high frequency antenna, but some designs manage to achieve this.
