DRAKE R-4C Especificaciones descargar pdf (Pagina 13)

stationary and rotate the knob skirt until the

dial displays the correct frequency.

3-6.

XTALS.

In the NORM setting of this

position switch, the

proper crystal for reception of the various amateur

bands is selected by the BAND switch (except at

the

setting). The numbered positions of this

switch correspond to the accessory crystal sockets

mounted at the rear of the receiver. When the

switch is set to a numbered position, the crystals in

the socket having the same number will be connec-

ted to the circuit for accessory band operation.

(The range window, just to the right of the XTALS

control, provides a convenient place to write in the

frequency covered in each accessory band). The

band switch must then be operated in accordance

with table 2-l

3-7. BAND.

This six position switch selects the amateur band

desired during normal operation. It also is used to

select the proper RF circuits for the various tuning

ranges when use is made of accessory crystals for

other frequency ranges. Correct setting of the

BAND switch during accessory operation is shown

in table 2-1.

3-8.

PRESELECTOR.

Rotation of this control changes the tuning of the

antenna,RF, and premixer coupling coils. The

outer ring of numbers, around the base of this con-

trol indicates the general setting for the various

bands. Fine adjustment for peak reception is made

after the signal is tuned in. A scale calibrated from

0 through 10 is provided for logging. See figure 3-2

for setting for out-of-amateur-band operation.

3-9. PASSBAND TUNING.

The

PASSBAND

TUNING control adjusts the posi-

tioning of the BFO with respect to the receiver

passband but without changing the frequency to

which the receiver is tuned. This control operates

in the SSB, CW 1 .5 CW

.25

modes. The

curved lines above the knob indicate

the

relative

bandwidths and positions of the passbands. The

knob

pointer

indicates the position of the BFO

with respect to the passband. The longest line in-

dicates the passband width of the 2.4 kHz filter

used in

the

SSB mode. The dot at the left end of

this

line

shows

the

normal setting of the BFO with

respect to the passband for LSB reception. The dot

at the right end of this line shows the normal posi-

tioning of the BFO for USB reception. However, to

emphasize lower audio frequencies and

reduce

high

pitched interference,

the

control may be adjusted

slightly closer to the passband (toward 12 o’clock

position). Conversely, to emphasize higher frequen-

cies the

PASSBAND

TUNING control may bc set

to position the BFO slightly farther away from the

passband than

the

dot indicates. Note that because

the received frequency is not changed when the

PASSBAND

TUNING control is moved, selection of

USB or LSB with this control is possible with

retuning of the PTO to keep the receiver tuned to

the same carrier frequency. Careful adjustment of

this control

can

result in markedly improved recep-

tion under heavy interference conditions. When the

kHz crystal filter has been installed in

the

1.5 mode,

the

second longest line in-

dicates the relative width and position of this filter

passband. Again the

PASSBAND

TUNING knob

shows the position of the BFO with respect to this

passband. When the 500 Hz or 250 Hz filter has

been installed in the CW

or CW

.25

position,

the shortest line above the

*PASSBAND

TUNING

knob is used. When tuning in a CW signal, the re-

ceived signal will be centered in the passband. The

BFO frequency (as indicated by the relative posi-

tion of the

PASSBAND

TUNING) must be offset

by the amount needed to produce the desired beat

frequency. Normally the correct setting will be just

beyond either the left or right end of the line cor-

responding to the bandwidth of the filter in use.

For higher beat note frequencies, the knob must be

moved farther beyond the end of the passband line.

For RTTY reception of

2125 and 2975 tone fre-

quencies, the

PASSBAND

TUNING control should

be in

the

RTTY area.

3-10. GAIN.

The GAIN control consists of two concentric con-

trols. The inner control is the AF Gain and is ad-

justed with the knob. The AF Gain control varies

the audio output from the receiver by varying the

3-4

1 2 ... 8 9 10 11 12 13 14 15 16 17 18 ... 28 29

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