FREQUENCY SPECTRUM CONGESTION

The situation that occurs when many stations transmit simultaneously using frequencies that are close together, i.e., with insufficient width of frequency guard bands or channel spacing. Note: Frequency spectrum congestion causes (a) difficulty in discrimination by tuning , (b) overlap of (i) a sideband and an adjacent carrier , or (ii) upper and lower sidebands, respectively, of adjacent carriers, and (c) interference that occurs when frequencies shift slightly or are phase shifted by ionospheric reflection . [ From Weik '89 ]