Heathkit SG-8 Assembly And Operation Manual page 7

USE OF THE I F SIGNAL GENERATOR
This signal generator can be used to align radio receivers. It furnishes a source of radio fre¬
quency or modulated radio frequency by means of signal generator fundamental frequencies be¬
tween 160 kc and 100 megacycles (1 megac? cle equals 1000 kilocycles) e nd useful harmonics of
the signal generator may be used to over 200 megacycles.
The RF Signal Generator will be found a most valuable aid to the radio service man as well as
the hobbyist. The day-to-day "bread and b itter" job of the signal generator is receiver align¬
ment. To save time and money, the servic e man or hobbyist should us< a technique which can
be applied to the majority of sets encountered in normal work. After us ing the technique a few
times, it becomes virtually a matter of "second nature" and so easily used that the average set
may be completely aligned in a matter of minutes.
The majority of single band radio receivers have nowadays become quite standardized and there¬
fore it is seldom necessary in alignment o receivers to refer to the specific manufacturer's
alignment instruction. In the average rec< iver, it is generally only necessary to take note of
the IF frequency (most home radios and aul Dmobile radios employ a 455 KC IF frequency).
Figure 13 is a schematic diagram of a small, single-band superheterodyne radio receiver. The
majority of single-band sets use a circuit similar to this one. Variations likely to be found are
as follows:
(1) Use of an antenna coil rather than a rod-type or loop antenna.
(2) Use of a separate oscillator rather than a pentagrid converter.
(3) Trimmer tuning of IF and RF stages in place of iron core slugs.
(4) Use of an RF stage ahead of the mixer.
(5) More than one IF stage.
These variations do not appreciably affect the alignment technique and the following step-by-
step procedure may be used directly in most cases:
(1) Turn both the signal generator and the receiver on and allow severa minutes for both units
to reach normal operating temperature. (It is a good idea to leave the signal generator on
during all working hours.)
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Page 17