The McKay Dymek DR 22 & DR 22C
General Coverage Communications Receiver

Chris J Arthur VK3CAE
 

This series of the American designed and built McKay Dymek receivers was produced in limited numbers from 1977 to 1980. They have a distinct 1970's hi-fi component style which is somewhat unique for a communications receiver. Many early PLL type receivers exhibited phase noise and intermod problems but the DR 22 and DR 22C were nothing short of excellent in these areas, however they did have a price supporting this (and some). In 1979-80 the DR 22C was available here in Australia through VICOM and at that time the price was a whopping $1600 + AU, as a result only a few units were ever sold in VK.

Those who know of the DR 22 would be familiar with its bullet proof front end and the strange tuning scheme used by its early programmable divider circuit. A  separate rotary switch is employed for each decade of a 5 digit display, with the exception of the last digit. A ± 5 kHz Fine Tuning knob was mounted under the last digit for sliding ether side of the 5 kHz minimum resolution step. Earlier model DR22's did not have a Noise Limiter function, both the DR 22 and DR 22C are quite rare. There was also a DR 33 model but as far as I know none of these ever made it over here to Australia, if you know likewise please let me know.


 

Features:       Phase locked loop, Digital synthesis tuning control with 5 digit LED display.
                        High level RF front end for excellent intermodulation rejection and sensitivity.
                        Class D AM envelope detection for low distortion at high modulation percentages.
                        Crystal filters in 1st and 2nd IF's with a Ceramic filter in the 3rd (triple conversion).
                        Switch selectable Bandwidth filtering of 8 or 4 kHz in the 3rd IF (455 kHz).
                        Fixed 5000 Hz audio heterodyne Notch filter
                        NL, IF Output Jack, Mute Line, Fine Tuning.

 

Accessories: DS111 Speaker, DA100 Active Antenna, 19RM22 Rack Kit, DP40 RF Preselector.
 

Circuit Description and Block Diagram for the DR 22

Incoming RF energy from the antenna is passed through a steep roll off 30 MHz low pass filter to a Broad Band RF Amplifier with switching for through, bypass and attenuator operation (not shown on block diagram). A high level Double Balanced Mixer is driven by the 1st local oscillator which consists of a PLL frequency synthesizer and RF Amplifier. The use of a high level LO (5 - 10mW) and double balanced mixer arrangement works well in limiting intermodulation and receiver overload problems. The DR 22 synthesizer is controlled by a multi-switched programmable divider with frequency selection being displayed on a large 5 digit LED display.

A first IF of 30 MHz is employed, thus the output of the double balanced mixer is passed through a 30 MHz Crystal filter. The 2nd IF also employs Crystal filtering (not ceramic) but the LO frequency of 40.7 MHz can be moved ± 5 kHz, this allows for tuning / sliding between the minimum divider step of 5 kHz. A final IF of 455 kHz is fed by switch selected 4 or 8 kHz Ceramic Filter.

Detection for the AM mode is carried out using the Class D AM envelope detection method this provides for low distortion levels at high modulation percentages. Demodulation of SSB/CW signals is carried out by the conventional Balanced Demodulator and BFO (455 kHz) method. Prior to audio amplification all AF signals pass through a 5000 Hz audio heterodyne Notch Filter.




 

Specifications:      Made In United States 1977-1980
                                Coverage: 50 kHz - 29.700 MHz
                                Readout: Digital LED display.
                                Modes: AM / LSB / USB
                                Circuit: Triple Conversion (30MHz - 10.7MHz - 455kHz)
                                Selectivity: 8 kHz @ -6 dB or 4 kHz @ -6 dB  (switchable)
                                Sensitivity: AM = 10 uV @ 100 kHz, 3 uV @ 300kHz & <1.5 uV @ > 400 kHz
                                Sensitivity: SSB = 5 uV @ 100 kHz, 1.5 uV @ 300 kHz & < 0.5 uV @ > 400 kHz
                                Intermodulation: 65 dB to 1 uV
                                Cross Mod: 65 dB to 1 uV
                                Image Rejection: 75 dB
                                Voltages: 110 -120 / 220 - 240 VAC

                                Physical: 43cm x 13cm x 37cm  6.8 kg  (17.5x5.1x15" 20 Lbs)
 

In August 1979 the now defunked Electronics Today International (ETI) magazine published a review of the DR 22 carried out by Roger Harrison (VK2ZTB) and Phil Wait (VK2ZZQ). The radio was supplied by VICOM Australia and had the serial number of 01519, it was later purchased by Bill Trenworth VK3ATW from Melbourne for what he described to me as "a hard to pass-up price". Bill was a friend to me and a valued member of the Moorabbin and District Radio Club, unfortunately he passed away late in 2000.
The DR 22 is now in my care.
 

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E-mail VK3CAE (Ex VK3JEG): cja@rmit.edu.au