Can you extend the antennas on the Bolt transmitter or receiver with coaxial cable?

While it's possible to use coax cable between the antenna array, or directional / omni-directional antennas and the Bolt TX or RX, it's not necessarily recommended as there will be loss associated with both the type of cable and the length of the cable.

Teradek cannot make specific recommendations on cabling or indicate the maximum length possible as it depends on a number of factors, but you can assume between 6 to 10 dB of loss per 100 feet. 

Be sure to use good quality cable rated for 6 GHz, and ideally it should be low loss cable.