How to Increase Wireless Distance?

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If you operate at vhf/uhf/microwave Frequncies -----raise the antennas very high & use directional antenna arrays like Yagi, dish.

Lower the frequency. UHF->VHF->HF->MF->LF. The earth's atmospheric layers become more reflective at lower frequencies. 28MHz can be used to get around the world. Of course, one does have to satisfy local licencing conditions in the choice of frequency to use...

Reduce the data rate of the transmitter and the bandwidth of the receiver, with good encoding systems the bandwidth required for speech can be reduced to about 10% of the non encoded system with a consequent increase in range

low frequency signals are propagated only through ground or water. they are usually used by the navy, however the challenge in using them is that it is easy to get all sorts of interferences.