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RADIO AND
OTHER
ACCESSORIES
RADIO
11-13
11-5 RADIO ALIGNMENT PROCEDURE
Figure ll-ll-Capacitor Mounted on Generator
Figure ll-12-Capacitor Mounted on Coil
figure ll-13-Static Collector Installed in Front Hub Grease Cap
Under no circumstance should alignment be
attempted without calibrated test oscillator and
output meter, or by untrained personnel.
These alignment instructions must be rigidly
adhered to" and all adjustments must be made
in the order given.
a. Alignment Preliminaries
The radio receiver should be functioning be-
fore the various aligning adjustments are made.
Trouble shooting, if necessary, should precede
t
h e final adjustment. Receiving signals at
correct dial setting depends upon having the
proper relation between tuning condenser and
the dial scale. Pointer or dial setting is neces-
sa r y because the scales are not linear with
frequency
and all scales are precalibrated for
maximum accuracy.
b.
Superheterodyne
Theory and Alignment
Buick Sonomatic Auto Radios employ the
superheterodyne circuit which uses an inter-
mediate frequency (I-F) amplifier, the charac-
teristics of which largely govern the selectivity
of the receiver. The I-F amplifier characteris-
tics are determined principally by the adjust-
ment and design of the I-F transformers. It is,
therefore, important that the I-F amplifier be
correctly adjusted to provide the best selectiv-
ity. These adjustments are in the form of iron
cores placed within the
coils.
During alignment
it is necessary only to adjust these iron cores
as specified in the tabulated alignment proce-
dure, to obtain best operation. Incorporated in
every superheterodyne is a local oscillator, the
output of which mixes with the incoming sig-
nal from the antenna. The local oscillator does
not operate at the same frequency as the in-
coming signal which is to be received. The
resonant (acceptance) frequency of the I-F
amplifier established the difference in frequency
required; 260 K.C. is used on Buick radios. The
local oscillator operates at a frequency higher
than the incoming signal, the two predominat-
ing resultant frequencies produced are the sum
and the difference of the two frequencies. The
design of these receivers is such that the differ-
ence in frequency is the same as the I-F ampli-
fier resonant frequency. Modulation of the in-
coming signal will be present as modulation of
input to the I-F amplifier.
c.
Effects
of R-F or I-F Misalignment
The effects of misaligned R-F or I-F stages
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