TABLE OF CONTENTS AM-band, shortwave, and VHF monitor receivers often produce output signals that are a terrible mess of weird squawks, squeals, and other assorted objectionable noises. Shortwave receivers in particular show a lot of weird signals, but the growing number of local electronic products are making the cacophony louder and messier than ever before. Fortunately, many of the interference problems that you ll see on your receiver can be fixed or at least reduced significantly in severity. Interference problems fit into two major categories: unwanted local radio station signals and unwanted radiation from other electronic devices.
Signals from AM, FM, and TV stations are quite powerful, so they can produce a number of problems for receiver owners in their immediate vicinity. Unfortunately, in many areas of the country, residences are located quite close to these types of stations (in a few areas, even shortwave stations are located near homes).
Typical problems from local transmitters include blanketing, desensitization, harmonic generation, and intermodulation. Let s look at each of these in turn.
The blanketing problem occurs when a very strong local signal completely washes out radio reception all across the band. It generally affects the band that the signal is found in, but not other bands. The offending signal can be heard all across the band or at numerous discrete points.
The desensitization problem is a severely reduced receiver sensitivity caused by the presence of a strong local signal. Desensitization can occur across a wide frequency spectrum, not only in...
