DRAKE R-4A Spécifications télécharger pdf (Page 22)

V THEORY OF OPERATION

A. R.F. Amplifier

A signal entering the antenna is applied to the grid of the low noise

12BZ6

R. F. amplifier tube

(Vl)

through the tuned circuit formed by the

coil

and capacitors C21 through C31.

Here it is amplified and the output is tuned by the circuit formed by

coil T2 and capacitors Cl through C11.

The signal is then applied to

the grid of the

6HS6

first mixer (V2).

B. First Mixer and Premixer System

A signal from the premixer system is applied to the cathode of the

6HS6

first mixer tube (V2), 5645 KC above the incoming signal frequency

applied to its control grid.

This results in 5645 KC I.F. output.

The premixer system consists of a 4955KC to 5455KC solid state

permeability tuned VFO T13, a switchable overtone crystal oscillator

Ql,

the premixer

V8, and

the premixer output circuitry composed of

T3 and T4 and their tuning and coupling capacitors.

The VFO signal is applied to the cathode of the premixer V8 and the

output of the crystal oscillator

Ql,

is applied to the grid.

The crystal frequencies are selected so that the difference frequency

output of the premixer is 5645 KC above the frequency of the desired

incoming signal.

For example, on 80 meters a 14.6 mc crystal is used in the crystal

oscillator. This frequency and the 4955

5455 KC VFO output com-

bine in the premixer stage to give output from 9145 KC to 9645 KC.

This signal is applied to the first mixer cathode through coils T3 and T4 and

their associated tuning and coupling capacitors to beat with the incoming

3.5-4.0 M

C signal.

This results in 5645 KC output.

Note that the RF coils

and T2 and premixer output coils T3 and T4 are

premeability tuned, and are ganged together. They are tuned by means

of the PRESELECTOR control.

-21-

1 2 ... 17 18 19 20 21 22 23 24 25 26 27 ... 38 39

Commentaires sur ces manuels

Pas de commentaire

DRAKE R-4A Spécifications Page 22

Commentaires sur ces manuels

Produits connexes et manuels pour Récepteur DRAKE R-4A