I have a project related to Signals of Opportunity and during my research on the communication signals that can be used for navigation purpose I saw that as references are given below signals that have smaller bandwidth give larger positional errors due to multipath effect. However, I could not find the reason why smaller bandwidthed signals are more prone to multipath effect compared to larger bandwithed signals. Could anyone point to any resources or give an explanation for why that is the case?
References: "The net bandwidth of FM signal is much narrower than even the GPS C/A code. This narrowness allows potential multipath errors." from https://navi.ion.org/content/69/2/navi.521