Heathkit SB-401 - TRANSMITTER OPERATION ONLY

Page 112
Figure 5-2
NOTE: Movement of the meter pointer, with the
Meter switch in the ALC position, indicates that
the Automatic Level Control stage is automat-
ically cutting down the final amplifier driving
voltage, There is nothing to be gained by modul-
ating so the pointer reaches peaks outside the
ALC area, since only distortion andinterference
to adjacent frequencies will result, See Figures
5-2, 5-3, and 5-4, These Figures illustrate
typical oscilloscope patterns, Plate current in
SSB will normally run between 80 and 100 ma,
No grid current will be indicated in this mode,
Relative power will normally run 1/4 to 1/3
of that indicated in CW,
The oscilloscope pattern in Figure 5-2 results
from CW or single-tone modulation, The meter
indicates full plate current of 240 ma,
The oscilloscope pattern in Figure 5-3 results
from SSB voice modulation, Notice the peaks on
on the oscilloscope pattern, They are sharp,
indicating a clean signal, andthey attain the same
Figure 5-3
Gag sesryxit
bbbb
Figure 5-4
height as the CW or "single tone'' pattern of
Figure 5-2, indicating maximum power input,
NOTE: Plate current peak reading is approx-
imately 1/2 of the amplitude, or less of the maxi-
mum "single tone" reading, due to meter inertia
and voice characteristics, Plate current is
approximately 100 ma,
The oscilloscope pattern in Figure 5-4 results
from SSB overmodulation, The meter reads
higher than before, but the scope indicates peak
flattening, Operation in this manner causes dis-
tortion and severe interference to adjacent fre-
quencies, Plate current is approximately 150 ma,
TRANSMITTER OPERATION ONLY
Before attempting to operate the Transmitter other than as a
transceiver, with the SB-303 Receiver, be sure to follow the
crystal installation and Heterodyne Oscillator Adjustment
described on Page 97 of this Manual.