Specifications

Page 16
Copyright 2006 Robert A. Larson, KC9ICH
V5, where they are amplified and then applied to the control grid of the Receiver Mixer, V6. The local oscillator signal from the VFO
Amplifier is then heterodyned with the received signal to produce the IF Frequency. All IF amplification is accomplished at this
frequency, nominally 5500.0 KHz, through IF amplifiers V7 and V8. In the Product Detector, V9A, the IF signal is heterodyned with
the carrier frequency generated by Carrier Oscillator, Q3. The resultant audio is then amplified by V9B, which then couples to the
AGC amplifier, V10, and the audio output stage, V11.
FREQUENCY CALIBRATION
Frequency calibration of the Model 1011D tuning dial is in 5 KHz increments. Dial accuracy and tracking are quite good, but caution
must always be observed when operating near band edges. Measuring the frequency with a frequency standard or marker generator
when working near band edges is recommended. The procedure for adjusting the dial calibration is covered in the OPERATION
section.
TRANSMIT AND RECEIVE SWITCHING
Transmit and receive switching is performed by relay K1. In TRANSMIT, only those tubes that operate in the transmit mode are
operative, all others being biased to cutoff through the relay contacts. In RECEIVE, with the relays de-energized, the tubes that are
used only in transmit are cut off in the same manner. Relay K1 when de-energized, applies signals from the output Pi-network to the
receiver. Note that relay K1 will not operate when the BAND SWITCH control is in the 27.0 REC position.
POWER RATING
The Siltronix 1011D is capable of over 200 watts P.E.P input under steady state two-tone test conditions. The peak envelope power,
when voice modulated, is considerably greater, typically 300 watts or more.
The built-in power supply produces a no-load plate voltage of approximately 830 volts. Under TUNE conditions, this voltage will
drop to approximately 680 volts and maximum input
power will be reduced considerably below the voice
P.E.P. rating. Under voice modulation, because
average power is considerably less, the power
amplifier plate and screen voltages will be maintained
higher, even during voice peaks, by the power supply
filter capacitors. Peak plate current will, therefore,
also be higher than with two-tone test conditions.
Under typical operating conditions, peak plate current
before flat-topping will be 380 mA at 800 volts, to
result in an input of about 300 watts P.E.P. Meter
readings of cathode current will not reflect this power
input, however, because of the damping in the meter.
Cathode current readings under normal voice input
should not average more than 100 to 120 mA.
POWER AMPLIFIER PLATE DISSIPATION
There is often a misunderstanding about the plate
dissipation of tubes operated as AB1 amplifiers under
voice modulation. In the Siltronix 1011D, while in
the transmit mode, and with no modulation, the plate
voltage will be approximately 830 volts, the plate
current 40 mA., and the power input 33 watts.
Authorities agree that the average voice power is 10 to
20 db below peak voice power. Normally, some peak
clipping in Conditions, the average power input will
be 80 watts, and average plate current will be the
power amplifier can be tolerated, and a peak-to-
average ratio of only 6 db may sometimes occur.
Under such conditions, the input power will be 80
watts, and the average plate current will be 100 mA.
With power amplifier efficiency of 65 percent, plate
dissipation will be approximately 26 watts. The 8950
is rated at 40 watts, continuous duty cycle. Thus it
can b
e seen that under normal operating conditions,
the Power Amplifier tube in the 1011D is not being
driven very hard. Note, however, that proper
modulation level must be maintained by correct setting of MIC GAIN and that the length of time in TUNE position must be limited to
not more than 10 seconds at a time.
FIGURE 5. CRYSTAL FILTER CHARACTERISTICS.