product detector tube V16, through the SIDE-
TONE control, to provide audio output from the
speaker for CW monitoring. Audio output from V2
is also applied to the grid of the VOX amplifier
tube, V19A, which causes relays K1 and K2 to
close. The relays turn on the transmitter, cause
the 9.0 MHz oscillator to be shifted to 9.001 MHz
and apply a variable source of DC, controlled by
half of the XMTR GAIN control, to the balanced
modulator. The DC voltage which unbalances the
modulator increases the carrier to a suitable level.
The resulting 9.001 MHz signal from the balanced
modulator is amplified by V15 and coupled into
the crystal filter. The SIDEBAND control must be
in the “X” position to allow the signal to pass. A
screen resistor is switched into the final amplifier
screen circuit to prevent excessive screen current in
the X-CW position of the Mode switch.
When the Mode switch is placed in the X-AM posi-
tion the AM screen modulator V14 is inserted in
series with the final amplifier screen supply and a
constant voltage is applied to the balanced modula-
tor. Relay K2 shifts the 9 MHz oscillator to 9.001
on transmit just as it does on X-CW. V
OX
and PTT
functions are the same on AM as on SSB.
When relay Kl is closed, either by the VOX circuit
or the push-to-talk switch, the cathode of V3B, V7,
Vl 1 and V12 are isolated from ground which dis-
ables the receiver.‘The cathodes of V4, V6, V8, V9,
V10 and V15 are connected to ground which actu-
ates the transmitter. Also, the antenna is switched
from the receiver input to the final amplifier tank
circuit. If the TCVR/RCVR switch is in the RCVR
position, the RCVR MUTE jack is grounded
through RFC 11 and RFC 7 and the antenna is
connected to the RCVR ANT jack instead of T9 in
the receive condition of the relays.
Pushing in the LOAD control disconnects the plate
current meter from the final amplifier cathode cir-
cuit and connects it to the diode D9 and its associa-
ted circuitry. This network samples the RF output
voltage at the antenna connection, rectifies it, and
applies it across the meter.
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