My apologies, I should have offered a bit of definition or explanation. Balun is synonymous with matching transformer. A Balun (
balanced to
unbalanced) is used to connect the antenna to the coax. On many of the Winegard and Antennas Direct antennas, the balun is built-in. Here's an example of a common balun / matching transformer :
http://www.winegarddirect.com/viewit...0%29&p=TV-2900
Computers, florescent lights, motors, engine ignition systems, etc. produce small amounts of radio signals that can range from low frequencies (AM radio band for example) to the UHF band and beyond. This wide range of frequencies is described by the term, 'broadband'. The closer the receiving antennas is to a device that produces some radio signal interference, the more likely the receiver will be interfered with.
Multipath is similar to an echo. Ideally, the receiving antenna would only receive signal directly from the transmitting antenna. However, radio waves are reflected off of metal, buildings, water, layers of the atmosphere, etc. Given that the shortest distance between two points is a straight line and any other path is longer, the signal from each path other than the direct path will arrive later, which means the direct and indirect path signals will be out of phase with each other and therefore work to cancel (interfere with) each other.
The bottom line is, double checking for water intrusion is the next indicated step. A factory built cable strung though a window or open door would be the only 'test equipment' needed to start. (Just a few drops of water wicked into the coax can produce these symptoms, you don't need to see water run from the coax as you disconnect it from the balun or grounding block.)
Oh, my dad is a retired tool & die maker... lot's of respect and admiration for the skills and knowledge...