Drake R-4C Instruction Manual

CHAPTER I
l-l. 1-2.
TABLE OF CONTENTS
INTRODUCTION
GENERAL DESCRIPTION .....................
MANUAL COVERAGE SPECIFICATIONS
.......................
.............
.....................
........
.-
.
Page
l-l l-l l-l l-3
CHAPTER II
2-l. 2-2. 2-3. 2-4. 2-5. 2-6. 2-7. 2-8. 2-9. 2-10. 2-11. 2-12. 2-13. 2-14. 2-15. 2-16. 2-17. 2-18.
INSTALLATION.
UNPACKING LOCATION
POWER REQUIREMENTS
GROUND...........................
ANTENNA. MUTE..
ANTI VOX. ..........................
INJECTION ..........................
CARRIER OSCILLATOR.
PTO LAMP. ..........................
SPEAKER...........................
ACCESSORY POWER.......................
ACCESSORY CRYSTAL FILTER INSTALLATION ACCESSORY CRYSTALS.
NOISE BLANKER ........................
CONNECTION TO T-4XC TRANSMITTER CONNECTION TO CONNECTION TO TR-4 OR TR-4C.
.................
..........................
..........................
..........................
.....................
.......
.....................
.....................
.............
.....................
...............
T-4/T-4X/T-4B/T-4XB
TRANSMITTERS.
.................
........
2-l 2-l 2-l
2-l 2-l 2-l 2-2 2-2 2-2 2-2 2-2 2-2 2-2 2-2 2-2 2-3
2-3
2-3 2-3
CHAPTER III
APRIL 1976
3-l. 3-2. 3-3. 3-4. 3-5.
3-6. 3-7. 3-8. 3-9. 3-10. 3-11. 3-12.
OPERATION . . . . . . -. . . . . . . . . . . . . . . . . . .
GENERAL. FUNCTION MODE.. MAIN TUNING DIAL DIAL CALIBRATION FRONT PANEL CONTROLS
XTALS............................
BAND.. PRESELECTOR PASSBAND TUNING
GAIN.............................
AGC.............................
NOTCH. ...........................
..........................
..........................
..........................
.......................
.......................
....................
..........................
.........................
.......................
3-l 3-l 3-l 3-l 3-l 3-l 3-3
3-4
3-4 3-4 3-4 3-4 3-5 3-5
TABLE OF CONTENTS (continued)
3-13. S'METER 3-14. 3-15. 3-16. 3
-
17. SSB 3-18. 3-19. 3-20. RTTY 3-21. 3-22.
PHONE-JACK. . . .
S'METER ZERO.
BASIC
CW AM
NOISE ADDITIONAL
CONTROL
RECEPTION . . RECEPTION .
RECEPTION. . . .
RECEPTION
BLANKER . .
TUNING RANGES
SETTINGS
. .
Page
3
5
3 5
.
3 5 3-
5 3 -6 3-6 336 3 -7 3-7 3-7
CHAPTER IV
4-l. 4-2. 4-3. 4-4. 4-5. 4-6. 4-7. 4-8. 4-9. 4-10. 4-11.
THEORY OF OPERATION.
GENERAL RF AMPLIFIER PREMIXER FIRST MIXER FIRST IF SYSTEM SECOND IF SYSTEM AND AGC
CIRCUIT. . . . .
S
METER . . . . . . .
AUDIO POWER CRYSTAL
AMPLIFIER . . . .
SUPPLY. . . . .
CALIBRATOR
DETECTORS
. . . . . .
. .
. .
CHAPTER V MAINTENANCE . . .
5-l. SERVICE DATA. 5-2. MAINTENANCE. 5-3. COVER REMOVAL. 5-4. TEST EQUIPMENT REQUIRED 5-5. TROUBLESHOOTING 5-6. ALIGNMENT INSTRUCTIONS. 5-7. 5-8. 5-9. FILTER MATCH ALIGNMENT. 5-10. 5-11. 5595 OSCILLATOR ADJUSTMENT 5-12. ANTENNA, RF AND INJECTION ALIGNMENT 5-13. S METER ADJUSTMENT. 5-14. CRYSTAL CALIBRATOR ADJUSTMENT
50kHz BFO AND 5645 OSCILLATOR ADJUSTMENT
NOTCH FILTER ADJUSTMENT
IF ALIGNMENT
. . . . . . . .
. . . .
. . . . .
. .
. . . . . . . .
. . .
5-2
5-2
441 441 4-l 4 -1 4-l 4-
1 4-2 4-2 4-2 4-2 4-2 4-2
5-l 5-l 5-1 5-
1 5-l 5-l 5 1 5-2
5-2 5 2 5-2 5 3 5 3
LIST OF ILLUSTRATIONS
Figure
1-1.
2-
1. 2-2. 2-3. 3-1. 3-2. 3-3. 3-4. 4-1. 5-l. 5-2.
5-3.
R-
4C
RECEIVER . . . . . . . . . .
VIEWING ANGLE OPTIONS. . . . . . .
REAR CHASSIS CONTROLS . . . . . . .
CONNECTING THE TR--4C. . . . . . .
FRONT PANEL CONTROLS. . . . . . . .
PRESELECTOR TUNING RANGES . . . . .
AM SELECTIVITY CURVES. . . . . . . .
SSB AND CW SELECTIVITY CURVES . . . .
BLOCK DIAGRAM . . . . . . . . . .
ALIGNMENT ALIGNMENT LOCATIONS, BOTTOM VIEW . . ACCESSORY NOISE BLANKER MODEL
SCHEMATIC DIAGRAM . . . . . . . . .
LOCATIONS,TOP VIEW
. . .
4-NB
Page
1 2
2-m
5 2-5 2-3 3-2 3-
7 3 8 339 443 557 5-8
.
5-8 5 --9
. . .
III
CHAPTER I
INTRODUCTION
1.1. GENERAL DESCRIPTION.
The R-4C Receiver is a triple conversion super­heterodyne receiver designed for optimum recep­tion of all types of amateur radio communications.
It provides complete coverage of the 80, 40, 20, and 15 meter amateur bands and 28.5 to 29.0 MHz of the 10 meter band with the crystals supplied. Additional/ coverage of 500 kHz segments between
1.5 and 30 MHz is possible with the addition of accessory range crystals. Sockets are provided for up to 15 additional crystals. A highly linear permeability-tuned solid state VFO and premixed injection give excellent stability and dial calibration on all bands. Eight pole crystal filter selectivity combined with passband tuning and a tunable notch filter provide superior interference rejection.
Three AGC time constants are selectable from the front panel and a 25 kHz crystal calibrator provides convenient markers at 25 kHz intervals throughout
the frequency range of the receiver.
1-2. MANUAL COVERAGE.
This manual is presented in 5 chapters and is ar­ranged for the convenience of the operator and service technician as follows:
Chapter I Chapter II
Chapter III
Chapter IV
Chapter V
Introduction (self explanatory). Installation. Describes the procedures
to be followed prior to operation.
Operation. Illustrates and describes front panel controls and describes operation in SSB, CW and AM modes.
Theory of Operation. Describes all critical circuits and networks.
Maintenance. Provides maintenance instructions and parts ordering infor­mation.
-
1.1
SPECIFICATIONS
Frequency Coverage
Accessory Coverage:
:
Covers 3.5to 4.0 MHz, 7.0to 7.5
21.5 MHz,and 28.5 to 29.0
MHz.
MHz,14.0to14.5MHz,
21.0to
15 accessory crystal sockets are provided. Coverage of any additional
500 kHz ranges between 1.5 and 30 MHz (except between 5.0 and
6.0 MHz) can be added by installing accessory crystals.
Modes of Operation:
SSB, CW, AM, RTTY.
Sensitivity: SSB Mode: 10 dB signal-plus-noise to noise ratio obtained on 80
10 M amateur bands with less than a 0.25 microvolt signal on the
antenna terminal, on other frequencies less than 0.5 microvolt signal.
Selectivity:
As supplied: SSB
Mode:2.4kHzat6dB,
AM
Mode:
8.0
kHzat6dB,28
4.2kHz kHzat
at60dB.
60dB.
With accessory crystal filters: AM Mode, 2 filters available:
CW
1.5,
6.0 kHz at6
4.0 kHz at6
CW
.5,
CW
1.5 kHz at6 500 Hz at6 250 Hz at6
dB,
10 kHz at 60
dB,
7.5 kHz at 60
.255
Modes, 3 filters available:
dB,
3.0 kHz at 60
dB,
1000 Hz at 60
dB,
600 Hz at 60
dB.
dB.
dB. dB.
dB.
M-
Stability
:
Calibration:
Spurious Responses:
Image Rejection:
Input Impedance: Audio Output Impedance: Audio Output: AGC:
After warm up, frequency will not drift more than +- 100 Hz, includ-
+-
ing voltage variation of Better than
+-
1 kHz when calibrated at nearest 100 kHz calibration
10%.
point. Internal spurious response less than the equivalent of a 1 microvolt
antenna signal on all amateur bands. (11.29 MHz above desired): Over 70 dB below 23 MHz, 60 dB above
23 MHz.
52 Ohms nominal.
3.2 Ohms to speaker, or headphones, 3000 Ohms anti
VOX.
0.7 Watt at AVC threshold, 2 Watts maximum at less than 5% T.H.D. Audio Output increases 3 dB maximum for a RF input increase of
100
dB
above AGC threshold. AGC threshold typically 1 microvolt. Attack time: 1 millisecond Release times: Slow: 1 second
Medium: 350 mSec Fast: 50 mSec
Power Consumption:
Size:
Weight:
60 Watts, 120/240 Volts AC,
50/60
Hz.
5.5 inches high, 10.75 inches wide, 12.25 inches deep overall. 17 pounds.
1-3
CHAPTER II
INSTALLATION
2-1. UNPACKING.
Carefully remove the receiver from the shipping carton and examine it for evidence of damage. If any damage is discovered, immediately notify the transportation company that delivered the receiver.
Be sure to keep the shipping carton and packing
material, as the transportation company will want
to examine them if there is a damage claim. Keep­ing the carton and packing is recommended in any case, as having these available makes packing the receiver much easier should it ever be necessary to store it or return it to the factory for service.
Inspect the packing material before putting it away to be sure you have not overlooked any accessory hardware. The hardware consists of two studs,
l0-24,5/8
No. Examine your R-4C to make sure that all tubes and crystals are properly seated in their sockets.
Fill out the enclosed registration card and return it to the factory immediately to insure registration and validation of the warranty.
2-2. LOCATION.
The location of the R-4C is not critical, as long as allowance is made for adequate air circulation. Avoid extremely hot locations. It is recommended that a minimum clearance of one inch be main­tained at each side of the R-4C. Do not cover the top with books, paper, or pieces of equipment.
With the studs and rubber feet supplied, it is sible to position the R-4C for either of two alter­nate viewing angles, as shown in figure vert the R-4C to either option, the first step is to remove the bottom cover from the receiver. Re­move the bottom row of three screws on each side of the receiver, and the cover can be removed.
Remove the rear feet, and snap the small rubber
feet into the holes just outboard from the original
inch long, and two small rubber feet.
NOTE
pos-
2-l.
To
con-
rear feet. For option B, put the bottom cover back on the receiver. For option C, remove the front feet from the receiver, invert them, and remount them on the same screws. Then thread one of the accessory studs into each of the remounted front feet. Finally, mount the feet that were removed from the rear of the receiver on the studs, and put the bottom cover back onto the receiver.
2-3. POWER REQUIREMENTS.
CAUTION Operation of this receiver with the wrong power source may result in serious dam­age.
Refer to figure 2-2. As shipped from the factory the R-4C is wired for 120 Volt operation. The receiver may also be operated from 240 V AC by removing the retaining tab and plac­ing the 120/240 Volt slide switch on the rear panel in the 240 Volt position. Replace the retaining tab on the opposite mounting screw to prevent the switch from accidentally being returned to the
120 V position. Operation of the receiver from
240 V with the switch in the 120 V position will cause serious damage.
2-4. GROUND.
A screw terminal is provided on the rear panel for connection to the station ground. Also, if used with the T-4XC transmitter and other accessories, con­nect a ground strap between the ground terminals of all units.
2-5. ANTENNA.
The jack labeled ANT is the connection point for the antenna. The nominal impedance of the circuit is 52 Ohms.
50/60
Hz AC
2-1
2-6. MUTE.
2-11. SPEAKER.
The MUTE jack provides connections for external standby-receive switching. The external circuit must isolate the MUTE jack center conductor from ground for standby, and connect it to the MUTE
jack ground for receive. The R-4C is shipped with
a shorted phono plug in this jack. When used with a transmitter, remove the shorted plug and connect the appropriate cable to the transmitter MUTE
jack.
2-7.
ANTI VOX.
High impedance audio is available at the ANTI VOX jack for use with the anti
VOX circuit of the
transmitter.
INJECTION.
2-8.
The phono jack marked INJ. provides a means of coupling the premixer system of the R-4C to the Drake T-4,
T-4B, T-4C,
T-4X, T-4XB or
T-4XC transmitters for transceive operation.
2-9. CARRIER OSCILLATOR.
The jack marked CAR. OSC provides a means of coupling injection from the T-4XC carrier oscilla­tor to the R-4C receiver. This connection phase­locks the two units to exactly the same frequency when used in the SSB Transceive mode. No connec-
tion is made to this jack for use with the T-4X or T-4XB transmitter.
2-10. PTO LAMP.
This jack provides a ground return for the pilot lamp behind the PTO dial. The R-4C is shipped with a shorted phono plug in this jack so that the lamp will light. When the R-4C is used with the T-4XC transmitter, remove the shorted phono plug and connect a cable between the PTO lamp
jacks of the two units. The lamp will then light
only when the T-4XC TRANSCEIVE switch is in the RCVR, SEPARATE, or SPOT positions. In the
XMTR position, the lamp will not light to indicate
that the R-4C PTO is disabled.
The audio output from the receiver is available at the jack marked SPKR. The output impedance is
3.2 Ohms.
2-12. ACCESSORY POWER.
The accessory power socket, labeled ACCY POWER,
located on the rear of the chassis, provides power
for operating accessories. Maximum load is 6.3 Volts AC at 300 milliamperes and 12 Volts DC at 50 milliamperes. A connection to the antenna is also available. The socket mates with a Cinch type 5AB2
plug.
2-13. ACCESSORY CRYSTAL FILTER
INSTALLATION.
To install additional crystal filter(s), proceed as follows: Remove the two screws holding the filter cover bracket for each position in which a filter is being installed. The upper position is for the .250 kHz filter, the center position is for the .500 kHz filter, and the lower position is for the 1.5 kHz filter. If a filter for the AM mode is being installed, remove the top cover of the
R-4C,
the mode
switch cover and remove the filter cover bracket
and the 150 Ohm jumper resistor from the AM
filter socket. Very carefully plug each filter straight
into the sockets.
After installing all the filters desired, replace the cover brackets over each filter and tighten the
mounting screws. Do not attempt to use accessory
filters without installing the brackets as it is very important to have a solid ground connection be­tween the bottom of the filter and the spring material.
2-14. ACCESSORY CRYSTALS.
By inserting the appropriate crystals in the acces­sory crystal sockets at the top rear of the chassis, it is possible to add up to 15 additional tuning ranges
(each 500 kHz wide) to the coverage of the R-4C. With the exception of the band from 5.0 to 6.0 MHz, these additional ranges may be anywhere be­tween 1.5 and 30 MHz. Only series resonant crystals
2-2
should be used for accessory coverage. Selected crystals for accessory coverage with the R-4C will be supplied by the R. L. Drake Company at a nom­inal cost. Contact Customer Service Department at the address given in paragraph 5-l for price and delivery information. crystal frequency for any additional range, see table 2-l which shows the required crystal frequen­cy and the proper BAND switch setting for the R-4C for the frequency spectrum from 1.5 to 30 MHz, except for the 5.0 to 6.0 MHz range. How­ever, if you are going to transceive with the Drake T-4, the crystal selection table in the transmitter manual
should be followed in selecting accessory crystals.
Remove the screws holding the shield/cover over the 15 accessory crystal sockets on the rear panel. Install the desired crystals and replace the cover and its mounting screws.
2-15. NOISE BLANKER.
To install the optional 4-NB Noise Blanker, re­move the top row of three screws on each side of
the R-4C. Remove the cabinet top. Remove the jumper plug from the noise blanker socket which is located toward the rear of the receiver, on top of the chassis. Retain the jumper plug so that it may be used if the 4-NB should ever require service. The 4-NB mounts on the four plastic stand-offs which are on the metal shields on either side of the PTO. Align the plastic stand-offs with the four holes in the 4-NB circuit board with the 4-NB cable toward the rear of the R-4C. Carefully push the 4-NB onto the stand-offs until it snaps into place. Dress the 4-NB cable toward the rear of the receiver and through the notch in the filter shield just above the NB socket and under the mode
switch cover. Plug the 4-NB into the NB socket
of the R-4C.
T-4B, T-4C,
To determine the correct
T-4X,
T-4XB,
or
T-4XC,
Turn on the receiver and tune in the crystal cali­brator signal. Detune the PRESELECTOR until calibrator signal S meter reading is around Temporarily unplug the 4-NB cable and reinstall the jumper plug. Compare S meter readings. If the
l/2
gain varies more than and the jumper plug, adjust R12 (blue potentiom­eter on 4-NB) until S meter readings are equal when switching between the 4-NB and the jumper plug. Replace cabinet top.
2-16. CONNECTION TO T-4XC
TRANSMITTER.
For interconnection diagram see the T-4XC in­struction manual.
2-17. CONNECTION TO
T-4XB
Connect as indicated in the transmitter instruction manual. No connection will be made to the CAR OSC jack and the shorted phono plug should be left in the PTO LAMP jack. Follow the instructions in the transmitter manual for Transceive Alignment if necessary. When making the adjustment, set the R-4C PASSBAND TUNING at 12 o’clock and the MODE Switch to SSB. Other control settings are the same as stated for the R-4/R-4B. The adjust­ment on the R-4C is C59 located on a PC board on the top of the R-4C chassis (see figure 5-l). Adjust this capacitor for zero canary chirps.
2-18. CONNECTION TO TR-4 OR TR-4C.
To use the R-4C as an external receiver with the TR-4/TR-4C illustrated in figure 2-3.
TRANSMITTERS.
transceiver, make the connections
S unit between the 4-NB
T-4/T-4X/T-4B/
S5.
2-3
Table 2-
FREQUENCY FREQUENCY
RANGE
2.01.5 -
222-
CRYSTAL
c
12.6
1.
Crystal
BAND RANGE
1.5 --3.0
Frequency
16.5--1 17.0
Chart
CRYSTAL
27.6
BAND
21.0
2.0--2.5
2.5
- 3.0
3.0
- 3.5
13.1
13.6
14.1
3.5-- 4.0 14.6*
4.0 - 4.5
4.5-- 5.0
6.0
-
- 6.5
6.5-- 7.0
7.0
-
- 7.5
7.5-- 8.0
8.0-- 8.5
8.5-- 9.0
9.0
-
- 9.5
9.5-- 10.0
-
- 10.5
10.0
-
15.1
15.6 3.5
17.1
17.6
1
18.1
* 7.0 21.0-- 21.5
18.6
19.1
7.0 22.0-- 22.5 33.1
19.6
20.1
7.0
7.0 23.0-- 23.5 34.1 28.5
20.6 7.0
-
21.1
@
1.5 --3.0
1.5 --3.0
17.0-- 17.5
17.5--18.0
28.6
28.1
-
3.5 18.0-- 18.5
3.5
3.5 19.0-- 19.5
7.0 20.0-- 20.5
7.0
18.5-- 19.0
19.5-- 20.0
20.5-- 21
.0
31.6 21.0
29.6 21.0
30.1
30.6 21.0
31.1
332.1* 21.0
7.0
21.5--22.0
32.6
21.0
22.5-- 23.0
23.5-- 24.0
14.0
24.0-- 24.5
33.6 21.0
34.6
28.5
21.0
21.0
21.0
21.0
21.0
21.0
28.5
o
10.5-- 11.0 11 .o-- 11.5 1 1.5-- 12.0
12.0
-
- 12.5
I
12.5-- 13.0
13.0
-
- 13.5 24.1
13.5-- 14.0
14.0
-
- 14.5
14.5-- 15.0
15.0
-
- 15.5
15.5-- 16.0
16.0
-
- 16.5
*Supplied with receiver
21.6
22.1
22.6
23.1
14.0
23.6
24.6
2225.1*
25.6
26.1
@
14.0
26.6
27.1
14.0 24.5-- 25.0
14.0
25.0-- 25.5 36.1 28.5
14.0 25.5-- 26.0
14.0
14.0
26.0-- 26.5
26.5-- 27.0 37.6
27.0-- 27.5
37.1
35.6
_
36.6
38.1
-
14.0 27.5-- 28.0
14.0
14.0 28.5-- 29.0 39.6*
28.0-- 28.5
.
29.0-- 29.5
38.6
0
28.5
3
39.
1
40.1
28.5
14.0 29.5-- 30.0 40.6
21.0
28.5
28.5
28.5
28.5
28.5
28.5
28.5
m
28.5
2-4
CHAPTER
III
OPERATION
3-1. GENERAL.
Figure 3-l illustrates and describes the front panel controls. Refer to the text in this chapter for de­tailed operating instructions. Rear chassis con­nectors are identified in figure 2-2.
3-2.
FUNCTION.
With the FUNCTION switch in the OFF position, the primary of the power transformer is disconnec­ted 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 in­stalled, 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 short­ing plug (supplied with the R-4C) must be inserted into the Mute jack in order to obtain NB and CAL operation.
MODE.
3-3.
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.
.5
In the CW 1.5, CW 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,
CW the appropriate rear panel socket.
3-4.
This dial has 2 transparent discs which display con­centric scales and which rotate at different speeds. Zero to 100 kHz is indicated on one disc and hun­dreds of kHz is indicated on the other. The fre­quency of the operating signal is the sum of the frequencies indicated by the BAND switch and the Main Tuning Dial, for example:
or CW
MAIN TUNING DIAL.
BAND switch setting
100 kHz dial
1 kHz dial
Received frequency
.25
mode until a filter is installed in
and CW
.25
modes, the
7.000 MHz .200 MHz .026 MHz
7.226 MHz
The
MODE switch determines the desired selectivi­ty 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 acces­sory 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 8
pole response in the AM mode. The Passband
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
FRONT PANEL CONTROLS
1. S Meter: Indicates relative signal strength.
Calibrated in S units from 1 to 9. Above 9 the
scale is calibrated in decibels.
2. FUNCTION Switch: Selects standby, external mute and crystal calibrator functions and switches in the Model 4-NB Noise Blanker. Also turns the Receiver on and off.
3. MODE Switch: Selects Receiver operating mode.
4. Main Tuning Dial: Displays a portion of the received frequency from zero to 500 kHz. The reading must be added to the BAND switch setting to determine the exact frequency.
5. Main Tuning Control: Adjusts frequency set­ting of the Main Tuning Dial.
6. AGC Switch: Selects the release time constant of the automatic gain control circuit (slow: S; medium: M; fast:
7. NOTCH Control: Attenuates heterodyne in­terference in all modes of reception.
F)
or turns off the AGC.
8. PASSBAND TUNING Control: Adjusts the positioning of the BFO in SSB and CW modes.
9. Phone Jack: Provides a connection for head-
phones.
10. PRESE LECTOR Control: Tunes the antenna, RF and premixer coupling coils.
11. GAIN Control: Knob adjusts AF gain. Lever
controls RF gain (normally in full clockwise position).
12. XTALS Switch: Selects accessory crystals for
accessory band operation position transfers crystal selection function to BAND switch for amateur band operation.
13. BAND Switch: Selects amateur band desired
when XTALS switch is in NORM position. Also selects proper RF circuits for accessory crystal operation (refer to table 2-l for correct setting).
(
15 positions). NORM
3-3
stationary and rotate the knob skirt until the dial displays the correct frequency.
3-6.
XTALS.
In the NORM setting of this 16 position switch, the proper crystal for reception of the various amateur bands is selected by the BAND switch (except at the
1 .5
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 connec­ted 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.
PRESELECTOR.
3-8.
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 con­trol 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.
knob
pointer
indicates the position of the BFO with respect to the passband. The longest line in­dicates the passband width of the 2.4 kHz filter
the
used in this
line
SSB mode. The dot at the left end of
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 posi­tioning of the BFO for USB reception. However, to emphasize lower audio frequencies and pitched interference,
the
control may be adjusted
reduce
high
slightly closer to the passband (toward 12 o’clock position). Conversely, to emphasize higher frequen­cies 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
1
.5
kHz crystal filter has been installed in
the
CW
1.5 mode,
the
second longest line in­dicates 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 .5 or CW
the shortest line above the
*PASSBAND
.25
position,
TUNING knob is used. When tuning in a CW signal, the re­ceived 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 cor­responding 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 quencies, the be in
the
PASSBAND
RTTY area.
2125 and 2975 tone fre-
TUNING control should
no
The
PASSBAND
TUNING control adjusts the posi­tioning 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 .5 CW
curved lines above the knob indicate
.25
modes. The
the
relative
bandwidths and positions of the passbands. The
3-4
3-10. GAIN.
The GAIN control consists of two concentric con­trols. 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
audio voltage applied to the audio amplifier stages. The outer control which is adjusted with the lever is the RF Gain control. This control increases the AGC threshold or bias level on the RF and IF stages which prevents signals below a certain level from being received. Normally this control should remain in the full clockwise position.
3-11.
AGC.
This switch selects the release time constant of the
automatic gain control circuit or turns off the AGC.
In the OFF position, the receiver gain may be con-
trolled manually with the RF gain control. In the
(fast
release). M (medium release), or S (slow re-
F lease) positions, the AGC is operative. The release time constant is approximately 1 second in the S position, 350 milliseconds in the M position, and
50 milliseconds in the F position. Attack time is 1
millisecond in F, M, S modes.
3-12.
NOTCH.
The NOTCH control can be used effectively in all modes of reception for attenuation of heterodyne interference from a carrier near the desired carrier. A permeability-tuned T-notch filter in the 50 kHz IF is used for this purpose. The filter produces a deep notch which can be tuned across the IF by rotation of the NOTCH control knob. On any mode of operation, an unwanted carrier is attenuated by tuning the notch across the receiver passband until the unwanted carrier is removed by the notch filter. Since the notch filter will remove the wanted car­rier just as readily as an unwanted carrier, the NOTCH control must be maximum effectiveness. In the SSB, CW 1.5, CW or CW
.25
modes, the PASSBAND TUNING will al-
adjusted carefully for
-5,
so affect the NOTCH frequency. Therefore, the PASSBAND
TUNING control should be set before the NOTCH control is adjusted. However, after ob­taining a notch, the PASSBAND TUNING may be moved slightly to fine tune the notch for maxi­mum null. When a notch is not needed, the NOTCH control should be returned to the detent in the OFF position.
3-13. S METER.
The S Meter indicates relative signal strength, and is a convenient indicator for peaking the tuning of the receiver. The lower (left hand) portion is cali­brated in S units from S-l through S-9. Above S-9 the scale is calibrated in decibels. Each S unit is equal to approximately 5 proximately 30 microvolts input to the antenna
Jack.
3-14. PHONE JACK.
dB.
An
S-9
signal is ap-
The phone jack is used when private listening is desired. Connection of the headphones automa­tically mutes the speaker output. While headphone impedance is not critical, a good quality set of 600 Ohm phones will work well. If 8 Ohm headphones are used, a pad should be connected between the phone jack and the phones to reduce the audio power to a reasonable level for the phones. Normal­ly connecting a 100 Ohm resistor in series with the
8 Ohm headphones will provide adequate attenua-
tion.
3-15. S METER ZERO.
NOTE The antenna should be disconnected from the R---4C while making this adjustment.
The S meter zero control is on the rear panel of the
R-4C.
It may be used to set the S meter needle to
S-l under no-signal conditions.
3-16. BASIC CONTROL SETTINGS.
For operation in any mode, preset the following
controls as indicated: a. SetFUNCTION switch to ON.
b. Set
BAND switch to Desired Amateur Band.
c. Set
XTALS switch to NORM. d. SetNOTCH control to OFF. e. SetRF GAIN lever fully clockwise.
3-5
f. Set AF GAIN knob to a comfortable level.
3-18 CW RECEPTION.
g. Set PRESELECTOR control to center of band
segment marked on panel. After desired signal is tuned in, adjust for maximum S meter reading.
3-17. SSB RECEPTION.
a. Make the basic control settings listed above. b. Set MODE switch to SSB. c. Set
PASSBAND
TUNING to the dot at either
the LSB or USB position as desired. d. Set AGC switch to S. e. Tune in station with Main Tuning knob.
f. Adjust PRESELECTOR for maximum S meter
reading.
After tuning in a station as described above, addi­tional adjustments may be made to further improve reception under various conditions or operator preferences.
g. Normally the AGC time constant S is optimum
for SSB but for rapidly changing signal condi­tions, it may be desirable to switch to the AGC release time constant M. The F or OFF positions will not normally be desirable for SSB reception.
h. The PASSBAND TUNING control may be
justed
slightly away from the dot at the LSB or
ad-
USB position to emphasize low or high frequen­cies. The fine adjustment of this control is large­ly one of operator preference, and the setting should be the one which produces the most pleasing audio response or minimum interference.
Under extremely adverse interference conditions the 1.5 kHz bandwidth crystal filter may be used to advantage for SSB reception if this accessory filter has been installed. Careful adjustment of the
PASSBAND
TUNING control will aid in the effective use of this restricted bandwidth for SSB reception.
The NOTCH control may be used to attenuate an interfering heterodyne. See paragraph 3-l 2 for adjustment of this control.
k. If impulse type noise interference is a problem,
the accessory 4-NB Noise Blanker may be
installed. The Noise Blanker may then be activa­ted by placing the FUNCTION switch in the NB
position.
Make the basic control settings listed in para-
a.
graph 3-l6.
b.
Set the MODE switch to SSB if the 2.4 kHz bandwidth filter is desired. If one of the narrow­er bandwidth accessory crystal filters has been installed it may be selected with the MODE switch.
C.
Set the PASSBAND TUNING to the dot at LSB or USB if the SSB mode is used. If the 1.5 kHz accessory bandwidth is used, set this control just beyond one end of the second longest line. If the
500 Hz or 250 Hz filter is used, set the
PASS­BAND TUNING just beyond one end of the shortest line.
d.
Set the AGC switch to S.
e.
Tune in a CW signal with Main Tuning knob for maximum S meter reading.
f.
Adjust PRESELECTOR for maximum S meter reading.
After tuning in a station as described above, addi-
tional adjustments may be made as follows:
If a different frequency beat note is desired, re­tune the MAIN TUNING for desired beat note while keeping the signal peaked for maximum
strength with the PASSBAND TUNING control. Faster AGC release time constants may be selec-
ted with the AGC control. If desired, the AGC may be switched OFF and the gain controlled manually with the RF GAIN lever.
The NOTCH control may be used to attenuate interfering undesired heterodynes. See paragraph 3-l 2 for adjustments of this control.
The accessory 4-NB Noise Blanker may be used
if impulse noise interference is a problem.
3-19. AM RECEPTION.
Make the basic control settings listed in para­graph 3-16.
Set MODE switch to AM. Tune in station for maximum S meter indication.
d. Peak PRESELECTOR for maximum signal
strength.
3-6
e. Medium or Fast AGC time constant may be
used if desired.
f. Additionally, the NOTCH filter may be used if
necessary to attenuate interfering heterodynes.
See paragraph 3-l 2.
g. The 4-NB Noise Blanker may be used if impulse
noise interference is a problem. The 4-NB will
function on AM as well as
SSB/CW.
3-20. RTTY RECEPTION.
Make the basic control settings listed in para-
a.
graph 3-l 6.
Set MODE switch to SSB; or, if the 1.5 kHz fil-
b.
ter has been installed, this position may be used. Also, if the 500 Hz filter has been installed, this filter may be used for narrow shift RTTY reception.
PASSBAND
Set
C.
TUNING to the RTTY region.
Make fine adjustment for optimum reception. Tune in station with MAIN TUNING knob.
d.
Adjust PRESELECTOR for maximum S meter
e.
indication.
f.
It may be desirable to use the M or F AGC time constant.
The NOTCH control may be used to attenuate
g.
interferring heterodynes. See paragraph 3-l 2.
h. The 4-NB Noise Blanker may be used if it has
been installed.
3-21. NOISE BLANKER.
This accessory is activated by placing the FUNC­TION switch in the NB position. The Model 4-NB Noise Blanker can be used on any type of reception.
It is most effective on short duration noise impulses such as those generated by automotive ignition systems. Refer to paragraph 2-l 5 for installation instructions.
3-22. ADDITIONAL TUNING RANGES.
By inserting the appropriate crystals in the acces-
sory crystal sockets at the top rear of the chassis, it
is possible to add up to 15 additional tuning ranges (each 500 kHz wide) to the coverage of the R-4C. With the exception of the band from 5.0 to 6.0 MHz, these additional ranges may be anywhere between 1.5 and 30 MHz. In order to receive with an accessory crystal,
the XTALswitch
of the R-4C must be set to the number corresponding to the accessory crystal socket into which the crystal was plugged. The lowest frequency of the accessory range may then be marked in the range window for reference. The marking is easily erased when crystals are changed. Refer to figure 3-2 for the recom-
mended tuning range for each band.
10
9
8 7
8
5
4 3
2
1
0
1.5
2 3 4
NOTE:
SOLID LINE INDICATES RECOMMENDED RANGE FOR EACH BAND.
Figure 3-2. Preselector Tuning Ranges
BAND
5
6
7 8 9
FREQUENCY (MC)
3.5
10
7.0
15
14.0
20 30
21.0 28.0
3-7
CHAPTER IV
THEORY OF OPERATION
4-1. GENERAL.
Refer to the block diagram figure 4-l and the schematic diagram figure 5-3 as required for the following circuit descriptions.
4-2. RF AMPLIFIER.
Jl
Signals from the antenna are fed from to permeability-tuned transformer Tl , and are applied to the grid of V1 through the tuned circuit formed by Tl and capacitors Cl through Cl 2. The amplified signal is coupled from the plate of VI to the grid of V2 through the tuned circuit formed by permeability-tuned coil T2 and capacitors Cl8 through C28.
4-3. PREMIXER.
The premixer system includes a transistorized per­meability-tuned VFO, crystal-controlled oscillator Q12, premixer tube V6, and the output circuitry consisting of T3 and T4 and the associated tuning and coupling capacitors. The PTO is tunable from 4955 kHz to 5455 kHz. The output of the PTO is applied to the cathode of V6. The output of crystal­controlled oscillator Q12 is applied to the grid of V6. The crystal selected to control oscillator Q12 is determined by the settings of the XTALS and BAND switches. The frequency of the crystal selec­ted will always be such that the difference frequen­cy obtained by heterodyning the output of the PTO with the output of oscillator Q12 will be 5645 kHz higher in frequency than the desired signal frequency.
4-4. FIRST MIXER.
The output of premixer V6 is coupled to the first mixer V2 through the permeability-tuned premixer output coils, T3 and T4, and their associated tuning and coupling capacitors. Heterodyning of the pre­mixer output and the RF amplifier output in V2 results in a difference frequency output of 5645
(ANT.)
Tl
the
and
.5
or
PASS-
In the
signal
pass-
.5
or
kHz from V2. Gang tuning of the RF coils T2 and the premixer ouptut coils T3 and T4 is used to maintain a fixed frequency relationship among these variable circuit elements. The output from V2 is applied to the input of a four pole crystal lattice filter with a bandwidth of approxi­mately 8 kHz.
4-5. FIRST IF SYSTEM.
The output of the crystal filter is applied to the gate of fied output of this stage is fed first through the noise blanker, if it is used, and then to grid 1 of V3, the 2nd mixer. Here the 5645 kHz IF signal is mixed with the BFO. In the SSB, CW 1.5, CW CW 5645 kHz IF signal and the BFO or approximately 5695 kHz depending on the setting of the BAND TUNING control. In the AM mode the BFO is off and V3 functions as a buffer amplifier with the output at 5645 kHz. The output of V3 is fed through the MODE switch S2 to the appropriate 8 pole crystal filters. In the AM mode the 5645 kHz IF signal may be fed through a filter or fed directly to stage V4 depending on whether an accessory, filter is installed in the AM filter SSB, CW 1.5, CW passes through the 8 pole crystal filter with a center frequency of 5695 kHz. As the frequency of the BFO ING control, the desired sideband or portion of the 5645 kHz IF signal is positioned within the
band of the 5695 crystal filter. The output of the
crystal filter is then applied to the grid of V4 through the MODE switch, S2. In V4, the 5695
kHz signal is mixed with a 5645 kHz oscillator in
the SSB, CW 1.5, CW AM mode the 5645 kHz signal is mixed with a
5595 kHz oscillator. The output of V4 is tuned to the difference frequency of 50 kHz by the IF trans­former (T7C). The Q of
position of the MODE switch. In the CW
CW provide additional selectivity.
Ql,
the 5645 kHz IF amplifier. The ampli-
.25
modes the output of V3 is the sum of the
p osition.
.5,
and CW
Q5
is varied by C86, the PASSBAND TUN-
.5
.25
position, the high Q tap is connected to
.25
modes
or CW
T7C
.25
modes. In the
is changed by the
4-1
4-6. SECOND IF SYSTEM AND DETECTORS.
The 50 kHz signal from T7C is coupled to the grid
V5
through the T-Notch filter T8 and its associ-
of
V5
ated circuitry.
further amplifies the signal before it reaches the detectors. The signal path from IF transformer T10 is determined by MODE
Q5
switch S2. In the AM mode, the BFO
is off. Detection is accomplished by diode CR4 and the resulting audio is amplified by Q6. In the SSB, CW
1.5, CW
.5
or CW
.25
modes the BFO is on. The BFO and IF output both feed the product detector consisting of diodes CR2 and CR3. The MODE switch selects the audio output of either Q6 on AM or the product detector on other modes and applies the audio to the audio amplifier section.
4-7.
AGC CIRCUIT.
The output of the 50 kHz IF amplifier V5 also is applied to Q7, the AGC detector. Q7 is biased past
cutoff under no-signal conditions. As the amplitude
V5
of the signal from
is increased, a point is reached where Q7 begins to conduct during a portion of each cycle resulting in a negative DC voltage being developed across resistor R50. Depending on the position of the AGC switch, a combination of capa­citors C73, C74, and C76 will be charged by this DC voltage. The release time of the AGC is deter­mined by this capacitor combination and R50. ‘The negative-going AGC voltage is applied to various filtering and delay networks and then to the grids of
V1,
V3 and V5. Counterclockwise rotation of the RF GAIN control increases the negative bias on the AGC controlled stages, limiting their gain. Isola­tion of the mute line from ground also allows the AGC line to swing negative, cutting
to approximately 40 Volts the three stages and muting
off
the receiver.
4-8. S
METER.
The S Meter is connected across a bridge circuit which has the plate of
V5
as one arm of the bridge, and the plates of V2 and V4 as the other arm of the bridge. Increasing signal strength results in the
V5
application of AVC voltage to the grid of
caus­ing the plate current to decrease thus unbalancing the bridge and causing the S Meter to deflect up
scale. Potentiometers R32 and R33 are used to set
the bridge balance point, determining the zero ad-
justment of the S Meter. The current characteristics
of the plate circuits of V2 and V4 are such that line voltage variation does not affect the zero set-
of the
ting
bridge circuit. The sensitivity of the S Meter is determined by the setting of potentiometer R36, which is in series with the S Meter.
4-9.
AUDIO AMPLIFIER.
The audio amplifier consists of a direct coupled, Class A, transformer output audio amplifier con-
sisting of Q9,
Ql0, Ql 1, T13 and other associated
parts. T13 has two secondary windings; one to
match a speaker or headphone output and a high
impedance winding for antivox voltage. The audio
gain is varied by R72, the AF GAIN control, at the
Q9.
input of
Negative feedback is used to reduce
distortion and increase stability of the amplifier.
4-10.
POWER SUPPLY.
power supply consists of transformer T14 and
The
the associated circuitry. CR8, CR9, Cl 63, R114, and C 164 form a full-wave, center-tapped configura-
tion to supply 150 Volts DC. CRlO, CR1 1 and Cl 67 form another full-wave rectifier to provide 12 Volts DC for the solid state stages. Q2, Cl 66 and
R116 form a filter to reduce the ripple on the 12 Volt supply. Negative bias voltage is obtained from half-wave rectifier CR7 and Cl 62.
4-11.
CRYSTAL CALIBRATOR.
When the FUNCTION switch is turned to the cali­brate position, a ground is supplied to the calibrator
circuitry. Q14 is a crystal controlled oscillator at
100 kHz. The output from Q14 is fed to CR1 6 and Q15 which shape the waveform to trigger the first J-K flip-flop in Ul . The 100 kHz is applied to the clock input causing the flip-flop to change state once every cycle of the input, thus dividing by two. The output of the first flip-flop is applied to the clock input of the second J-K flip-flop which again divides by two. The output of this flip-flop is a 25 kHz square wave which is applied to the antenna of the receiver through the coupling network.
4-2
CHAPTER V
MAINTENANCE
5-1. SERVICE DATA.
We will check and align your receiver at the factory for a nominal fee if it has not been tampered with. Transportation charges are extra. Any necessary repairs will be made on a time and material basis. Please write or call the factory for authorization before returning your receiver for alignment or service. Address your request for authorization to:
R. L. Drake Company 540 Richard Street Miamisburg, Ohio 45342 ATTN: Customer Service Department
Telephone: (Area Code 5 13) 866-3211
Code-A-Phone Service after
1630 Hours E.S.T.
5-2. MAINTENANCE.
WARNING Disconnect the R--4C from the power source before removing the covers. High
voltage which is present at several points
can cause a lethal electrical shock.
Careful consideration has been given in the design of the R-4C to keeping maintenance problems to a minimum. However, it is quite possible that some problem will arise which cannot be solved by tube substitution. If this occurs, we suggest that you either return the unit to your dealer, or write direct to our Service Department, describing your problem in detail. Include full information concerning ex­ternal connections, control settings, tubes substi­tuted, serial number, etc.
5-3. COVER REMOVAL.
a. Remove the three top screws on each side of the
R-4C.
b. Remove top cover by first pulling up on the rear
and then on the front of the cabinet.
c. Remove the six bottom screws from the sides of
the R-4C.
d. Lift the R-4C chassis out of the-bottom cover.
5-4. TEST EQUIPMENT REQUIRED.
a. Stable RF signal generator with calibrated out-
put attenuator and a frequency range of 50 kHz to 30 MHz.
b. Frequency counter or oscillator accurate to with-
in 50 Hz at 5.645 MHz. c. VTVM with 11 megohm input impedance. d. A 12.6 MH
the 1.5 through 2.0 MHz segment, if this band is
to be aligned. An accessory crystal for reception of the WWV
standard frequency transmission that is most reliably received in your area.
A scale with Two 10 K
5-5. TROUBLESHOOTING.
The R-4C has been designed so that tubes can be replaced without need for realignment. The best method of finding defective tubes is by direct sub­stitution. Do not rely too heavily on a tube checker.
The voltage and resistance charts, tables 5-l and
5-2 should be valuable in isolating minor problems. However, no attempt should be made to service the R-4C unless you are thoroughly familiar with electronic circuitry and servicing technique. Care should be taken not to disturb the lead dress in the R-4C. It is critical in several circuits.
5-6. ALIGNMENT INSTRUCTIONS.
Turn receiver on and adjust for SSB reception.
Z accessory crystal for operation of
l/32
inch divisions.
l/2
W resistors.
5-1
5-7. 50 kHz BFO AND IF ALIGNMENT.
a
Apply signal of exactly 50.000 kHz to pin 2 of V4 (6EJ7). (Maximum frequency error of 25 Hz.)
b
c d.
e.
PASSBAND
Set
(12 o’clock position).
control to exact center of range
Set MODE switch to CW Tune Tl 1 for zero beat. Tune
T7C
and Tl0 for maximum negative volt-
.5
or CW
.25
position.
age on AGC line or for maximum S meter reading.
50
f. Disconnect
5-8. 5645 OSCILLATOR
kHz signal from V4.
ADJUSTMENT.
a. Connect signal generator or oscillator to pin 2 of
V2 (6EJ7).
b. Set generator frequency with counter to exactly
5645.000 kHz. Accuracy should be within
50
Hz.
c. Adjust
C59
(top trimmer on second mixer oscil-
lator board on top of chassis) for zero beat.
d. Disconnect generator from V2.
ward the front panel). The pointer on the knob should be at the nine o’clock position. If it isn’t,
loosen the knob setscrew and position the knob
at the nine o’clock setting. Tighten set screw. Turn NOTCH control until it goes into the detent (slug completely into coil). The knob should be at the “OFF” position.
Tune in signal generator on any band, SSB Mode.
b.
dB
Set level for approximately 30 Set PASSBAND control to exact center (12
C.
over S9.
o’clock). Tune PTO for zero beat.
d.
Adjust NOTCH control for null. The knob
e.
should point very close to the 12 o’clock posi­tion. If it doesn’t, adjust the slug in the notch
coil until the null occurs at 12 o’clock. Be sure steps c and d have been performed before mak­ing any adjustment.
f.
Keep the NOTCH control adjusted for deepest null, and adjust R39 (the red potentiometer lo­cated on the longest PC board) for deepest notch.
5-9. FILTER MATCH ALIGNMENT.
a.
Tune in crystal calibrator signal on 80 M band. Set AGC switch to M.
b.
Turn MODE Switch to AM mode.
C.
Adjust PTO upwards in frequency until cali-
dB
brator level drops 20
d.
Adjust
T5
for maximum negative AGC voltage
(or 4 S units).
or maximum S meter reading.
e.
Set MODE Switch to SSB and PASSBAND
TUNING to center.
f.
Tune PTO until calibrator signal is zero beat. Turn PASSBAND TUNING control counter-
g .
clockwise toward LSB until S meter drops 25
dB
(or 5 S units).
Tune C42 and T6 for maximum S meter reading
h.
or maximum negative AGC voltage. If 2 peaks are observed on C42, choose the one at mini­mum capacitance.
5-10. NOTCH FILTER ADJUSTMENT.
a. Turn NOTCH control until the slug in the notch
coil is the greatest distance out of the coil (to-
5-l 1. 5595 OSCILLATOR ADJUSTMENT.
This oscillator affects only the AM mode. a. Tune in signal generator on any band in the SSB
Mode. b. Set PASSBAND control at exact center. c. Tune PTO for zero beat. d. Adjust NOTCH control for deepest null. e. Switch MODE switch to AM being careful not to
upset other control settings.
C60
f. Adjust
(lower trimmer on second mixer crystal oscillator board on top of chassis) for deepest notch.
5-12.
ANTENNA, RF, AND INJECTION
ALIGNMENT.
Turn off the receiver. Refer to figure 5-2 and determine the location of Sl D and Sl E (these are the third and fourth bandswitch wafers, counting from the front of the receiver). Locate these switch wafers in the receiver. Each of these switch wafers has two rotor contacts colored
5-2
green. Connect a 10,000 Ohm resistor from the more easily accessible of the two rotor contacts on Sl D to ground. From the corresponding rotor contact of Sl E, connect a 10,000 Ohm resistor to B+. The easiest point to make this connection is the red and white striped wire on the terminal strip near S 1 E.
Disconnect the antenna from the
b.
R-4C, connect a 47 Ohm resistor from the center of the antenna jack to ground.
Plug the 12.6 MHz crystal into one of the acces-
C.
sory crystal sockets.
d
Set the receiver right side up on the bench and
turn the PRESELECTOR knob as far clockwise as possible. Carefully measure the distance from
the top of the slug of Tl to the top of the white
liner projecting through the hole in the top of Tl
. The distance was set at the factory to exactly
9/l
6 inch. Check the measurement carefully be­fore altering the position of the slug. The dis­tance that the slug projects must be exactly inch. Check the setting of the slugs in T2, T3, and T4. All must have the same
9/l
6 inch pro-
jection.
Turn the receiver on, set the BAND switch to
e.
28.5, the FUNCTION switch to CAL, and tune in the calibrator signal at (28.7 MHz. Allow the
receiver to warm up for a few minutes.
Adjust the PRESELECTOR knob so the slugs in
f.
Tl
through T4 project exactly 15/32 inch above
the white liners. Refer to figure 5-1. Adjust the four trimmers
g-
marked 28.7 for maximum S Meter reading. If the calibrator signal is insufficient to produce an adequate S Meter indication, remove the 47 Ohm resistor from the antenna input, and connect the signal generator to the antenna input. Set the
R-4C FUNCTION switch to EXT. MUTE, ad-
just the signal generator to 28.7 MHz, and set
the generator output level to cause an S Meter
indication of approximately S-7. Adjust the four
S
trimmers marked 28.7 for maximum
Meter
indication.
h.
Repeat steps f and g for each band, using the
settings given below:
and
9/l
6
BAND
21.0
14.0 1 l/32
7.0
3.5
1.5
SLUG HEIGHT
7/l
6 inch
FREQUENCY
inch
3/l
6 inch Flush with White sleeve Flush with White sleeve
21.3 MHz
14.3 Mhz
7.3 MHz
3.8 MHz
1.9 MHz
NOTE: For the 1.5 band, the XTALS switch must be set to the position corresponding to the number of the socket into which the 12.6 MHz crystal was inserted .
i. Turn off the
R-4C,
and remove the alignment
resistors.
5-13. S METER ADJUSTMENT.
a. Tune in a 1 microvolt signal from the signal gen-
erator on the 40 meter band. Peak PRESELEC­TOR and PASSBAND for maximum strength.
b. Set S METER ZERO control on rear panel to
mid-range. Adjust R33 for S-3 reading. Remove signal and adjust the bias potentiometer
R5
5 for S-l reading.
micro
Apply a 30,000 METER sensitivity adjustment R36 for 60
signal and adjust the S
dB
over S-9.
Repeat steps a.through e. several times if
necessary.
5-14. CRYSTAL CALIBRATOR ADJUSTMENT.
Connect the antenna to the
a.
R-4C,
and set the receiver controls for AM reception of WWV. Tune in WWV.
b.
Refer to figure 5-l and determine the location of c174.
C.
Insert a shorted plug in the MUTE jack, and set the FUNCTION switch to CAL.
Adjust the audio gain until you can hear the beat
d.
note between WWV and the calibration signal.
e.
Adjust Cl74 for zero beat with the WWV signal.
5-3
Table 5-
Resistance Chart
1.
REF DES Type
Vl
v2 v3 v4 v5 V6
Q1
6BA6
6EJ7 470 100 K 470 6BE6
5.0M 6EJ7 470 6BA6
6EJ7 470 680 K 470
10M
2N5950 D:180 G:l
1
4M
2
0 0
0 0
1 M
0 0
K+
3
470
S:68
MEASURED AT PIN
4
0.01
0
0.01 0
0.01 0
-
5 6 7
5.5K
.0l
5.5 K .0l
5.5K .0l
-
9K
0
16 K
0
9K
0
-
8 9
0
6.5 K 12K
-
12K
--
6.5 K 42K
0
5K
-
6K
--
­0
0
­0
-
NOTE: All measurements were made with reference to chassis ground with an 11 megohm VTVM. Both GAIN
controls
fully clockwise. FUNCTION: off. MODE: SSB. AGC: slow. Antenna: discon­nected. BAND: 3.5. PRESELECTOR peaked on noise at 3.5. XTALS: NORM. Shorted plug in MUTE jack. AC line cord disconnected. Readings: +- 10%.
With
lead to xtal filter disconnected.
Table 5-2. Voltage Chart
REF
DES
Vl
v2
v3
v4
v5 V6
Q1 Q2
Qll
Type
6BA6
6EJ7
6BE6
6EJ7
6BA6
1
-1
.0-
-2.0
2.3
-1.
5-
1.8 0 1.8
-1
.o-
-2.0
6EJ7 2.0 -.5-
2N5950
EP487
D: 13.0
C:16.0
40310 C:14.5 B:l.l E:.45
2 3
0 0
0
2.3
0 0
0 0
-3.0 G:O
B:16.2
2.0
S:.75
E:15.5
NOTE: All measurements were made with reference to chassis ground with an 11
MEASURED AT PIN
4
6.3*
0
6.3*
0
6.3* 0
-
-
5 6 7 8 9
140
6.3*
125
6.3*
125 120 0
6.3*
-
-
--
55 0
-
0 130 120 0
40 -1.0
0
130 90
--
-
0 145
--
--
-
-
85 0
--
­_
megohm
VTVM.
-
0
-
-
-
Both GAIN controls fully clockwise. FUNCTION: on. MODE: SSB. AGC: slow. Antenna: dis­connected. BAND: 3.5. PRESELECTOR peaked on noise at 3.5. XTALS: NORM. Shorted plug
in MUTE jack. Line voltage: 1 17 Volts AC. Readings:
+-
10%.
*: AC Voltage.
5-4
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