DRAKE R-4A Especificaciones descargar pdf (Pagina 23)

Second Converter

The 5645 KC output of V2 is applied to the grid of the

12BE6

second

converter (V3) through a crystal filter.

This gives excellent cross mod-

ulation and overload characteristics by providing selectivity before the

gain producing stages.

The

cathode, control grid and screen grid are connected in a Pierce

oscillator configuration controlled by a 5595 KC crystal. The

5645

signal

is applied to the signal grid of this tube where it beats with

the crystal oscillator signal to produce 50 KC output.

50 KC I.F. System

The 50 KC output of the second converter V3 is applied to the grid of the

12BA6

IF amplifier tube V4 through the T-Notch Filter composed of T8 and

its associated circuitry.

Output of V4 is applied to the grid of the last

12BA6

IF amplifier (V-5)

through the

passband

tuner T9.

The

passband

tuner consists of four LC circuits with high Q.

Passband

tuning is accomplished by ganged permeability tuning of the

four coils, and variable selectivity is accomplished by changing the

coupling between the four tuned circuits.

DETECTOR SYSTEMS

The amplified signal

from V5 is applied to the AM detector composed

of diode D7 and

Q5,

to the AVC amplifier Q4 and to the product

detector diodes through the IF transformer,

Tl0.

When the SSB/CW-AM switch is in the SSB/CW position, the BFO, Q6,

is turned on applying 50 KC voltage to the product detector diodes, and

beats with the IF signal to produce an audio signal across the AF GAIN

potentiometer.

When the SSB/CW-AM switch is in the AM position, the BFO is turned

off, the AM detector is turned on and its output is connected to the AF

GAIN potentiometer.

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DRAKE R-4A Especificaciones Pagina 23

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