WhitakerAudio AM/FM Stereo Tuner 2012, Assembly & User Manual, Page: 141 / 166

141
AM/FM Stereo Tuner
usually be noticed and tuning should be adjusted for maximum quieting, which will coincide with
the maximum audio output point. Strong stations will frequently cause a triple tuning response to
be evident, a normal characteristic of most FM detectors not using automatic frequency control
(AFC). When tuning a strong station, a weak and distorted response will be noticed, followed by a
strong clear response and then another weak one. The strong response should always be used and
adjustment made for distortion free performance. Quieting on strong signals will be apparent over
a wide tuning range, but distortion on loud passages of music will be noticed if improperly tuned.
Although virtually all FM broadcasts today are stereo, improved sound reproduction may be
experienced with the FM mono position for weak stations. Solid-state tuners routinely switch to
mono (or blend to mono) at low signal levels and/or in the presence of certain types of
interference.
It is normal for some amount of drift to occur as the tuner warms up. The local oscillator will
tend to drift higher as the ambient temperature increases. A station properly tuned in right after
the tuner is turned on may need to be re-tuned (typically higher) after 5 minutes or so. After the
tuner has reached its characteristic operating temperature, the local oscillator is quite stable and
no further drift will result. This effect is more pronounced on weak stations.