Is there an easy way to calculate the loss of RF signal as it travels over coax cable? I think this is important when installing remote antennas for wireless mics.
Indeed it is important.
Shure has a remote antenna tool to help determine which cables and amplifiers to use at: Wireless Mic Remote Antenna Tool
Here is an online calculator for cable loss: http://www.timesmicrowave.com/calculator/
And another: http://www.net-comber.com/cable-loss.html
Also, see this document: https://522bb370f5443d4fe5b9-f62de27af599bb6703e11b472beadbcc.ssl.cf2.rackcdn.com/publication/upload/396/wireless-systems-guide-for-antenna-setup-english.pdf