The main tuning dial, which appears behind the large escutcheon, is accurately calibrated in
kilocycles on band #1 and in megacycles on the remaining three bands.
Note: The accuracy of the main dial calibration will hold only if the BAND SPREAD condenser is set at
minimum capacity, or the position indicated by "O" on the Band Spread dial.
When first using the receiver, become familiar with its operation on the standard broadcast band, or
Band #1, before tuning the short wave bands. You then will be able to fully appreciate the
capabilities of the Sky Champion.
TUBE LINE-UP
6SK7
R. F. Amplifier
6F6G
Audio Frequency Power Amplifier
6K8
Converter and Oscillator
6H6
Automatic Noise Limiter
6SK7
1st I.F. Amplifier
6J6GT
Beat Frequency Oscillator
6SK7
2nd I.F. Amplifier
80
Rectifier
6SQ7
2nd Detector, A.V.C. and 1st stage of
audio amplification
CONTROLS AND OPERATION
Reading from left to right the functions of the various controls will be described.
The R.F. GAIN control adjusts the sensitivity of the receiver by varying the cathode bias on the R.F.
and I.F. amplifiers. Maximum sensitivity will be obtained when this control is rotated to
the right as far as it will go. When this has been done a switch will operate which turns on the
calibrated "S" meter which may be obtained as a separate unit.
The BAND SWITCH selects the frequency range through which the receiver tunes.
When using the receiver for the reception of modulated, or telephone, signals it is advisable to
have the AVC switch set at ON.
For code or C.W. reception, the Automatic Volume Control circuit should be disconnected by setting
the A.V.C. switch at OFF. When this has been done the R.F. GAIN control should be manually ad-
justed so that the set will not overload or block on extremely strong signals.
The MAIN TUNING control adjusts the main dial of the receiver for reception on the desired fre-
quency.
The TONE switch turns the receiver ON and OFF and in the HIGH position produces natural reproduction.
In the MED. and LOW position, the highs are attenuated, a condition that will be helpful in receiving
signals during certain types of interference.
The BAND SPREAD TUNING control allows smooth back-lash - free operation of the separate band spread
condenser and dial.
The A.N.L. or automatic noise limiter switch will effectively minimize ignition and similar types
of interference which are objectionable to short wave reception. Best results are obtained with
the AUDIO GAIN control set near the minimum end.
The PITCH CONTROL and its associated BFO switch provide a beat note for the reception of C.W.
signals. The PITCH CONTROL, when the B.F.O. switch is set at ON controls the frequency of the beat
note which may be set to a pitch most pleasing to the listener.
The SEND-REC. switch removes plate voltage from the tubes in the receiver so that the set is
inoperative during stand-by periods, but leaves the tube filaments hot for instant use.
Any type of high impedance headset, crystal or magnetic, may be plugged into the jack marked PHONES.
Unless otherwise specified the S-20R Receiver operates on 117 volts 50/60 cycle since phase cur- rent.
A universal model is available on special order for operation on 110 or 250 volts, 25/60
cycle single phase current, at a slight increase in price.
