CARRIE R BALANCE
Once the CARRIE R BALANCE control is properly adjusted as described for SSB operation,
it
is
to be lef t in this position for all subsequent SSB, AM, and CW work. Partial carr ier unbalance is
obtained automatically at the AM position of the MODE switch by connection of resistor R42 between
one of the 7360 balanced modulator tube deflection plates and ground. This partial unbalance should
be exactly that required to set up the transceiver for AM transmission, provided that the CARRIE R
BALANCE control is properly adjusted as described for SSB operation. In the CW position of the
of the MODE switch, one deflection plate of the 7360 balanced modulator tube is automatically grounded
to provide complete carrier unbalance. Thus, in CW operation, the CARRIE R BALANCE control
setting has no effect.
CALIBRATION AC TIVATION
The 753 provides power and input connections for a lOOkc crystal oscillator employing a tube with
a 12. 6 volt heater. A 4-pin plug (EBY 11'9721-71) must be wired to the calibrator connection cable as
follows:
pin 1: 12.
6
volt heater
pin 2: Ground
pin 3: Calibrator signal output
pin 4: B+
The 4-pin plug may then be inserted in the CALIBRATOR socket on the rear apron. To activate
the calibra tor , the MIC GAIN control is turned fully ccw past the detent.
A F GAIN CONTROL
May be used as a volume control in listening with either a loudspeaker or headphones. However ,
most operators pref er to run the A F GAIN wide open (fully cw) for SSB and CW reception, and use the
R F GAIN control as a volume control.
R F GAIN CONTROL
May be set in accordance with the operator 's preferences, with, however , the understanding that
the S-Meter reading is aff ected by the setting. Nor mal S-Meter operation is obtained with this control
tu rned fully cw.
S-METER ZERO ADJ USTME NT
Set the MODE switch at SSB and the RF GAIN fully ccw. Adjust the S-ME TE R ZE RO control on
the rear apron for a zero S-Meter reading. The S-Meter will now read received signal strength or
background noise.
All other control adjustments and uses are described fully in the Operation section.
CIRCUIT DESCRIPTION
TRANSMITTING
Two stages of microphone amplification are provided by V lA and VlB. A sample of the speech
wavefor m is taken from the plate of V lA, before the MIC GAIN control, and applied to V3A, the VOX
amplifier . A description of the VOX circuit is given in the Receiving section.
Balanced modulation is eff ected with the 7 360 beam deflection tube, V2, which has as its grid in-
put signal the output of the 5. 2 mc crystal-controlled carrier oscillator , V4A. Audio from V lB is
applied between the deflection plates, and is R-C coupled through C7 and R9. The DC bias on the
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