Radio tuner specification referring to the ability to ignore or reject information from a radio frequency near that of the one actually tuned in and desired. The better a tuner is at this the more the unwanted stations are kept out. Think of listening to the radio and you hear your station but you also hear another station’s DJ in the background. This is an example of poor alternate channel selectivity. The channel not desired and not tuned in, the alternate channel, is interfering with the desired channel

Alternate channel selectivity is measured in decibels (dB), and a higher figure is better. Look for tuners featuring an alternate channel selectivity rating of 75 dB or higher. Low figures will result in tuners that cannot properly lock onto a single channel and keep out the “noise” from those channels around the desired one.