TABLE OF CONTENTS CHAPTER I INTRODUCTION l-l. GENERAL DESCRIPTION . . . . . . . . . . . . 1-2. MANUAL COVERAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . SPECIFICATIONS CHAPTER II . INSTALLATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l-l . . . . . l-l . . . .- . l-3 . 2-l . . . . UNPACKING . . . . . . . . . . 2-2. LOCATION . . . . . . . . . . . . . .
TABLE OF CONTENTS (continued) Page 3 5 . . 3-13. S'METER 3-14. PHONE-JACK. 3-15. S'METER ZERO. 3-16. B A S I C CONTROL SETTINGS . . . 3 5 . 3 5 3- 5 3 - 17. SSB RECEPTION 3-18. CW RECEPTION 3-19. AM RECEPTION. 3-20. RTTY RECEPTION 3-21. NOISE BLANKER 3-22. A D D I T I O N A L TUNING RANGES 3-7 THEORY OPERATION. 441 CHAPTER IV . . 3 -6 . . 3-6 . . 3 -7 . OF 336 . 3-7 4-l. GENERAL . 441 4-2. RF AMPLIFIER . 4-l 4-3. PREMIXER . . 4 -1 4-4.
LIST OF ILLUSTRATIONS Figure 1-1. R-4C RECEIVER 2-1. VIEWING 2-2. REAR 2-3. CONNECTING 3-1. FRONT . . . . . . OPTIONS. . . . . . . 2-m 5 . . 2-5 . . 2-3 . . 3-2 3-2. PRESELECTOR TUNING RANGES . . . . . 3- 7 3-3. AM SELECTIVITY CURVES. . . . . . . . 3 8 3-4. SSB AND CW SELECTIVITY CURVES . . . . 339 4-1. BLOCK . 443 5-l. A L I G N M E N T LOCATIONS,TOP VIEW . . . 557 5-2. ALIGNMENT LOCATIONS, BOTTOM VIEW . . 5-8 ACCESSORY NOISE BLANKER MODEL 4-NB .
CHAPTER I INTRODUCTION 1.1. GENERAL DESCRIPTION. the frequency range of the receiver. 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.
SPECIFICATIONS Frequency Coverage : Covers 3.5 to 4.0 MHz, 7.0 to 7.5 MHz, 14.0 to 14.5 MHz, 21.0 to 21.5 MHz, and 28.5 to 29.0 MHz. Accessory Coverage: 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 M10 M amateur bands with less than a 0.
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.
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. The audio output from the receiver is available at the jack marked SPKR.
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. To determine the correct 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.
Table 2- 1. FREQUENCY RANGE CRYSTAL 1.5 2 2 2 --2.0 CRYSTAL BAND 1.5 - 3.0 16.5 - 1 17.0 27.6 21.0 13.1 1.5 - 3.0 17.0 - 17.5 28.1 21.0 2.5 - 3.0 13.6 1.5 - 3.0 17.5 - - 28.6 3.0 - 3.5 14.1 3.5 18.0 - 1 8.5 3.5 - 4 .0 14.6* 3.5 18.5 - 1 9.0 29.6 21.0 4.0 - 4 . 5- 15.1 3.5 19.0 - 19.5 30.1 21.0 4.5 - 5 .0 15.6 3.5 19.5 - 20.0 30.6 21.0 6.0 - 6 .5 17.1 7.0 20.0 - 20.5 31.1 21.0 6.5 - 7.0 17.6 7.0 20.5 - 2 1.0 31.6 21.0 7.0 - 7.5 1 18.1* 7.0 21.0- - 21.
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.
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. 8. PASSBAND TUNING Control: Adjusts the positioning of the BFO in SSB and CW modes. 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. 9. Phone Jack: Provides a connection for headphones. 3. MODE Switch: Selects Receiver operating mode. 4.
stationary and rotate the knob skirt until the dial displays the correct frequency. 3-6. X T A L S . 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.
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. A G C . 3-13. S METER. The S Meter indicates relative signal strength, and is a convenient indicator for peaking the tuning of the receiver.
3-18 CW RECEPTION. f. Set AF GAIN knob to a comfortable level. 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.
e. Medium or Fast AGC time constant may be used if desired. h. The 4-NB Noise Blanker may be used if it has been installed. f. Additionally, the NOTCH filter may be used if necessary to attenuate interfering heterodynes. See paragraph 3-l 2. 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.
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. Signals from the antenna are fed from Jl (ANT.) 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.
4-6. SECOND IF SYSTEM AND DETECTORS. The 50 kHz signal from T7C is coupled to the grid of V5 through the T-Notch filter T8 and its associated circuitry. V5 further amplifies the signal before it reaches the detectors. The signal path from IF transformer T10 is determined by MODE switch S2. In the AM mode, the BFO Q5 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.
CHAPTER V MAINTENANCE 5-1. SERVICE DATA. c. Remove the six bottom screws from the sides of the R-4C. 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: d. Lift the R-4C chassis out of the-bottom cover. R.
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 Set PASSBAND control to exact center of range (12 o’clock position). c Set MODE switch to CW .5 or CW .25 position. d. Tune Tl 1 for zero beat. e. Tune T7C and Tl0 for maximum negative voltage on AGC line or for maximum S meter reading. f. Disconnect 50 kHz signal from V4. 5-8. 5645 OSCILLATOR ADJUSTMENT. b. C. d. e. ward the front panel).
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. b. Disconnect the antenna from the R-4C, and connect a 47 Ohm resistor from the center of the antenna jack to ground. C. Plug the 12.6 MHz crystal into one of the accessory crystal sockets.
Table 5- 1. Resistance Chart MEASURED AT PIN REF DES Type 1 2 3 4 5 6 7 8 9 Vl 6BA6 4M 0 0 0.01 5.5K 9K 0 - - v2 6EJ7 470 100 K 470 0 .0l 0 6.5 K 12K 0 v3 ’ 6BE6 5.0M 0 0 0.01 5.5 K 16 K 12K - - v4 6EJ7 470 1M 470 0 .0l 0 6.5 K 42K 0 v5 6BA6 10M 0 0 0.01 5.5K 9K 0 - - V6 ’ 6EJ7 470 680 K 470 0 .
