There is a real nasty RF noise source that I have had to track down and disconnect at several incidents;
It is known as a SNAP server. These little servers turn a whole network into a large, wideband rf noise source. The network guys always moan and cry when I kill the server but I point out that without radio communications to the field, we don't need to even have a network.
In other words, take the antenna off of a handheld scanner or better yet an amateur handheld with an S meter on it and start sniffing around the network.
Bruce