Tone Oscillator And Tone Amplifier - Heathkit SB-401 Assembly Manual

Grid-block type key control is used for V13B.
The output level of V13B to the receiver speaker
is adjusted by control R38 to suit the individual
requirements.
closing of the key ; and second, the output of
tone amplifier V12C is coupled to the receiver
speaker (by relay RL1) so the operator may hear
his keying during transmission. Tone oscillator V13B operates only when the
Mode switch is in the CW position. The output
audio frequency (approximately 1000 Hz) is
determined by the phase shift network (P.E.C.).
This audio tone is used to perform two func-
tions: first, to key the VOX amplifier so that
break-in CW operation is instantaneous with the
TONE OSCILLATOR AND TONE AMPLIFIER
(F igure 6-4)
Figure 6-4
- -
.01 .0 I
C/43
68
CI44
1M
47K
V13B
1/2 6J I I
TONE OSC.
R/54
-
-
RIJ9
470
+
CI.35
- 10
-
-
V12C
1/3
6010
SIOETONE
AMP.
..
- -
-
- -
RL1
PARTIAL
TONE
OUTPUT
LEVEL
TO
SPEAKER
T3
AUDIO
OUTPUT
TRANS-
FORMER
-
-
RI53
220K
OTUNE
CW
USB
o
-
M IF .-----.
",
."."
",
(
I
I
I
LSB
I
I -:
~// MIF
-
84-22
P.E.C.
___ .005
CI42
use cw
o
Q,....._----v
LSB QTUNE
RI52
1.5M
FIR
orr
TRAN
SPOT
TRCV
STBVO
TO VOX
AMPLIF IER
TO RECEIVE
AuDIO
B+
Page 128