I am installing a CB with twin antennas on my F250. The Coax is a lot longer than what is needed. Will coiling up the excess cable interfere with transmission/reception?
It usually makes no real problem - but of course, those weak signals will be reduced in level my too much cable. coiling cable can make a difference to impedance. Coils create additional inductance, made more effective if there is something metallic within the coil. So I suppose a coil could well create a mismatch that would have an impact.
In practical terms I’ve transmitted through a large coil of coax with the turns taped and it worked fine - but there are effects, but usually coils of unnecessary cable just reduce the output power and lower receive signal strength in practical terms.