Standing Wave Ratio (SWR)
The tuning of a signal transmitting antenna is more critical than that of a receive only antenna.  Although we pre-tune all antennas,  on vehicle fine tuning should be performed.

An SWR meter tells you how efficiently your antenna is transmitting the signal.  The lower  ...  the better.

CoPhased cable has a frequency just like an antenna does.  A mismatched cable length to an antenna can either make tuning easy (6' 0r 18') or impossible (12').  Because we tune all of our antennas to about Channel 1 we recommend you use 18' V-CoPhase harness of RG-59 to achieve a proper match.