Antenna Frequency Exceeds Range:

Example: You need only 860-960 MHz GSM band but the antenna covers 800-960MHz: One customer told us that using an antenna that includes 824-960 band allows too much interference, that comes from the low end of that band 824-860MHz.

Our recommended solution is to add a filter in your system board (or AP board), and thereby enable use of an antenna that covers a wider band, such as 800-960MHz or 824-960MHz, as examples: Because you will find many more antenna options that cover 800-960MHz or 824-960MHz than just 860-960MHz.

800-860MHz is a very close band to 860-960MHz  frequency band and the antenna is a passive device which can’t filter; therefore, you need to have an active circuit to filter 800-860MHz frequency.