Western Electric 407A-4, Инструкция по эксплуатации

Страница: 55 / 136

means of the "RF Output" control only.
If any tendency toward paras itic oscillations exists
after the above adjustments are completed, the neutraliz ing
of the third radio-frequency ampl ifie r should be che cke d.
This should b e done without changing any of the other radio­
frequency adjustments .
Adjustment of Sliders on R61A
The s liders on R61A provide the potentials for the
"RF
Output" control potent iometer. With this c ontrol at 20 and
all plate voltages on, the radi o-frequency output should b e
ess entiall y z ero . Rais ing the upper s lider on R6 1A will re­
duc e the output, while lowering it will increase the output .
With this s l ider adjuste d to give essentially z ero output,
s et the
"RF
Output" control at 85 and the Test Meter switch
on the 11V2 Grid X5" pos ition. If the grid current is not
within the s pecified l imits of 2 to 4 milliamperes, it will
be neces s ary to adjust the lower sl ider on R6 1A. Rais ing
this slider increas es the grid cu rrent as well as the
RF
Output of the transmitter. After the proper pos ition of
the lower s l ider has been determined, check the positi on of
the upper s l ider for z ero radio frequency output when the
"RF
Output" control is s et at 2011 • When the proper adjust­
ment of the s liders is obtained set the
nRF
Output" control
at 85 and readjust the "Output Coupling V2 " control until
normal carrier output is obtaine d. The final position of
the "Output Coupling V211 control should b e such that turn­
ing this control counter-clockwis e produces an inc rease in
antenna or output current .
Routine tests should b e made with the
"RF
Outputtt con­
trol to determine that carrier cut-off definitely takes
place when this c ontrol is between the l imits of 0 and 20.
This should b e done to as sure carrier cut-off when the pro ­
tective circuit of Unit D operates .
48