DRAKE R-4C Spezifikationen PDF herunterladen (Seite 11)

CHAPTER

III

OPERATION

3-1. GENERAL.

Figure 3-l illustrates and describes the front panel

controls. Refer to the text in this chapter for de-

tailed operating instructions. Rear chassis con-

nectors are identified in figure 2-2.

3-2.

FUNCTION.

With the FUNCTION switch in the OFF position,

the primary of the power transformer is disconnec-

ted from the line cord. In the standby (STBY)

position all operating voltages are applied to the

receiver circuits, but the receiver is muted. With the

switch in the ON position, the receiver operates

unmuted regardless of external muting connections.

The EXT. MUTE position is the same as the ON

position, except that receiver muting is externally

controlled through the MUTE jack on the rear of

the chassis. Switching to the NB position energizes

the accessory Noise Blanker, when it has been in-

stalled, without changing the muting function.

Switching to the CAL position energizes the 25

kHz Crystal calibrator without changing the muting

function. If external muting is not used, the short-

ing plug (supplied with the R-4C) must be inserted

into the Mute jack in order to obtain NB and CAL

operation.

3-3.

MODE.

The

MODE switch determines the desired selectivi-

ty and selects the proper detectors. In the AM

position, the AM detector is switched in. The IF

bandpass of the receiver is 8 kHz as determined by

the 4 pole 1st IF crystal filter and the two 50 kHz

tuned circuits. For additional selectivity an acces-

sory AM 8 pole filter can be installed in the internal

accessory filter socket in place of the 150 Ohm

resistor which is supplied. The selectivity then has

pole response in the AM mode. The Passband

Tuning is inoperative in AM mode. In the SSB

mode, the product detector is used. The 2.4 kHz,

8 pole crystal filter which is mounted internally

determines the selectivity. This mode is used for

normal SSB reception and can also be used for CW

and RTTY.

In the CW 1.5, CW

and CW

.25

modes, the

product detector is used. Selectivity is determined

by the accessory filter(s) which are installed in the

sockets on the rear panel. The passband tuning is

operative in the SSB and the three CW modes. Note

that the receiver will not operate in the CW 1.5,

.5,

or CW

.25

mode until a filter is installed in

the appropriate rear panel socket.

3-4.

MAIN TUNING DIAL.

This dial has 2 transparent discs which display con-

centric scales and which rotate at different speeds.

Zero to 100 kHz is indicated on one disc and hun-

dreds of kHz is indicated on the other. The fre-

quency of the operating signal is the sum of the

frequencies indicated by the BAND switch and the

Main Tuning Dial, for example:

BAND switch setting

7.000 MHz

100 kHz dial

.200 MHz

1 kHz dial

.026 MHz

Received frequency

7.226 MHz

3-5.

DIAL CALIBRATION.

The Main Tuning Dial may be calibrated by the

following procedure:

a. Set the FUNCTION switch to CAL and set the

PASSBAND TUNING control to 12 o’clock.

b. Tune the R-4C to zero beat with the nearest

25 kHz calibrator signal.

C. Hold the knob on the Main Tuning control

3-1

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