Main Page and Front and Side Views | Tank Coil Information |
Interior and Back Views | Typical Operating Conditions |
Circuit Description and Schematic Diagram | Power Supply Photos |
813 Tube Information | Power Supply Circuit Description and Schematic Diagram |
Operating Bias:
The operating bias on the amplifier can be set to any value from 0 volts to the
maximum available from the bias supply. However, experimentation has shown that
operating the tube by setting the bias for a zero signal plate current of about
10mA produces the best results. 10mA keeps the zero signal input to the
amplifier at about 25W and also provides a good bleeder load for the power
supply. At an output of 200W, the regulation of the power supply from zero
signal to 200W out is about 7.6%.
Maximum Power Output of 260 Watts:
Operating with the bias set for a zero signal plate current of 10mA, and driven
by the Wingfoot VFO exciter,
the 813 amplifier can produce an output of 260 watts on 40m as measured with a
Bird wattmeter. This is consistent with the 813 data
sheets.
Conservative Outputs of 250 Watts and 200 Watts:
Although the amplifier can produce 260 watts of output, the amplifier must be
carefully tuned to achieve this maximum. Cutting the drive back to an output of
250 watts is a little easier on the amplifier, and keeps the plate dissipation
well under the ICAS maximum of 125 watts. In most of my operating, I keep the
output cut even further back to 200W, since this is the legal limit on 30m,
where I often use the amplifier. This decrease of 1.1 dB from the maximum of
260 watts substantially reduces all operating currents and results in a cooler
and thus happier amplifier.
Drive Requirements and Input Impedance:
With the 1:4 input transformer, the 813 amplifier can be driven with either
tube or solid state transmitters. At 200W output the amplifier requires 16.5W
of drive from the exciter on a frequency of 7.020 MHz. This represents a power
gain of 10.8 dB. At 250W output the amplifier requires 26W of drive for a power
gain of 9.8 dB.
Summary of Typical Operating Conditions:
The first table below summarizes the operation of the amplifier at an output of
250 watts on the 40m band. The second table summarizes the operation of the
amplifier at a very conservative output of 200W. The third table indicates
typical zero signal conditions.
Parameter: | Value: |
Test Frequency | 7.018 MHz |
Power Output | 250 Watts |
Drive Power | 26 Watts |
Power Gain | 9.8 dB |
Plate Current | 160 mA |
Grid Current | 26 mA |
Screen Current | 7.5 mA |
Plate Voltage | 2241 Volts |
Plate Input | 359 Watts |
Plate Dissipation | 109 Watts |
Plate Efficiency | 70% |
Parameter: | Value: |
Test Frequency | 7.020 MHz |
Power Output | 200 Watts |
Drive Power | 16.5 Watts |
Power Gain | 10.8 dB |
Plate Current | 130 mA |
Grid Current | 21 mA |
Screen Current | 6 mA |
Plate Voltage | 2290 Volts |
Plate Input | 298 Watts |
Plate Dissipation | 98 Watts |
Plate Efficiency | 67% |
Parameter: | Value: |
Zero Signal Plate Current | 10 mA |
Zero Signal Plate Voltage | 2464 Volts |
Zero Signal Plate Input | 24.6 Watts |
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