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R. L. Drake Company, Miamisburg, OH

R - 4 C

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überarbeitet am 19.10.2010

The latest set in the R-4 series of Drake receivers was the R-4C introduced in 1973, it has a very similar appearence. The R-4C was Drake's latest tube equipped receiver, the succeeding SPR-4 broadcast band receiver was Drake's first solid state receiver.

Triple conversion, intermediate frequencies 5,645 / 5,695 MHz, 50 kHz

linear analog dial 1 kHz

ham bands and 15 additional cryszal controlled 500 kHz segments,
continuous coverage with the FS-4 frequency synthesizer.

AM, USB/LSB

Sensitivity 5 MHz
AM / SSB < 0,25 uV

Selectivity -6/-60 dB
SSB 2,4/4,2 kHz, AM 8/28 kHz, optional CW 0,25/0,6 0,5/1 1,5/3,0 kHz

RF-Gain, AGC 3x, PBT in SSB mode, Notch, (NB optional)

With it's dimensions of 14 x 27,3 x 29,7 cm and it's weight of 7,7 kg, the shape of the receiver is very similar to it's predecessors.

In the bright grey upper segment of the front panel, You find from the left side the signal strenght meter calibrated in S units and decibels over S9, the main switch to set the receiver in standby and operation mode and to activate the Noise blanking circuit and the Crystal calibrator. At it's right, You find the MODE switch - it sets the receiver to AM, SSB and CW operation and lets You chose the CW bandwidths. This is one of the major shortcomings of the R-4C: the IF bandwidths cannot be switched independently from the reception modes. For AM mode, the standard bandwidth is 8 MHz, the SSB bandwidth of 2,4 kHz is an excellent choice, for CW reception You can make a choice from 1,5, 0,5 or 0,25 kHz.
At the right, You find the analog frequency dial consisting of two concentric transparent plexiglass disks, displaying the frequency in 1 kHz steps, and the main tuning knob.

In the lower dark grey part of the front panel, You find six more controls. Leftmost in the upper row of the six controls, You will find the XTALS band selector for the fifteen additional crystal controlled 500 kHz segments and underneath the selector for the amateur bands, active when the XTALS switch is set to NORM position. In the middle, You find the preselector control with it's small red metal pointer, this has to be thoroughly set to the signal peak when tuning in a station. The Gain control underneath consists of two concentric controls. The normal knob is used to control the volume, the small metal handle controls the Rf gain, it is usually set to the most clockwise position. The controls at the right activate the NOTCH filter to eliminate an unwanted interfering carrier signal, the second knob underneath is the PASSBAND tuning control to shift the passband of the IF filter to the side of a signal, which is less compromised by an interfering adjacent channel signal.
In the right lower corner of the front panel, the AGC switch lets You select one of three AGC speeds, the AGC can be switched off for full manual control of the RF gain.

At the rear of the set, You find the RCA / chinch connectors for the external speaker, the antenna (!) and connectors used in transceive operation together with the matching transmitter.
In the middle of the rear side, the three optional CW filters can be installed; at the right, You find the cover for the sockets for the accessory crystals.
With a plain R-4C, continuous coverage from 1,5 - 30 MHz is not possible, You would need 55 crystals.

To correct this shortcoming, Drake did develop a solid state frequency synthesizer, the FS-4 plugs in in the socket of one crystal, You can chose the desired waveband by simply turning the knobs until the start frequency of the 500 kHz segment is displayed.
This accessory is extremely useful for the broadcast DXer. It has been sold only in small quantities, a second hand receiver coming together with the FS-4 synthesizer is worth double money as acquiring additional crystals for all interesting band is an expensive and cumbersome task.

When the receiver is switched on, the dial and S-meter will be illuminated with bright blue light. Now select the desired amateur radio band with BAND switch, the XTALS switch should remain in the normal position. In case You want to receive a signal from the 49m broadcast band, a matching crystal has to be fitted in the connector at the rear, a table in the operating manual will tell You about the correct settings of Bandswitch and Preselector. Adjust the preselector for maximum noise or signal strength; remember to adjust the preselector when cruising through a band - as long as the preselector is adjusted precisely, the receiver performs with an excellent sensitivity and rejection of unwanted and spurious signals. You can read frequencies from the dial with an accuracy of 1 kHz, two concentric plexiglass disks display the exact frequency.

After You have set the receiver to the desired frequency, several tools support You to improve reproduction of faint signals. The IF filters cannot be switched independently from the reception modes, there have been modifications to overcome tis major drawback of the R-4C. The PASSBAND tuning control lets You shift the filter passband to the direction of the less disturbed sideband to fade out interfering signals. The NOTCH filter is used to suppress an unwanted interfering signal, carefully tune its control until the hiss will disappear.

The performance of Drake's R-4C on the shortwave bands is superior. When the preselector is tuned carefully, sensitivity and selectivity are good and the stability is sufficient to copy radioteletype transmissions.
There is one major drawback: the IF bandwidth filters cannot be switched independently from the reception mode: there have been several proposals for modifications of the receiver.

further reading:
d/e: Drake R-4C at www.radiomuseum.org
e: The Drake R-4B and R-4C, Two Receivers From the Past, Jon Williams, fine tuning's proceedings 1989

© Martin Boesch 15.12.2008