Mount Evelyn DX Report: RETRO RECEIVER #6: KENWOOD QR 666

RETRO RECEIVER REVIEW #6

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KENWOOD QR 666

By Craig Seager VK2HBT

This time, we cast our eyes over an early solid state receiver from Kenwood - the QR 666. Somehow I doubt whether the selection of the model number “QR 666” was some oblique reference by Kenwood’s technicians to the biblical number of the beast, borne out of some apocalyptic vision of receivers to come. Interestingly, 666 is also said to be the sum of all the numbers on a roulette wheel. Either way, there wasn’t a “665” preceding it. In fact, it seems that the only attempt to bridge the gap between the very successful Trio-Kenwood 9R 59 series of receivers and the next general coverage offering was an amateur band only set - the R-599 - a pretty neat and well performed unit with brushed aluminium fascia that paired with the T-599 transmitter.

According to Fred Osterman's reference guide Shortwave Receivers - Past and Present, the QR 666 was launched around 1974 and continued until replaced by the similarly styled but slicker looking R-300 in 1976. The latter was advertised in the 1976 World Radio TV Handbook as “Kenwood’s new way to listen to the world”, and touted as “the last word in engineering design and craftsmanship”. Whilst the R-300 was admittedly no slouch, how far we have come since then!

The QR-666 was marketed under both the Trio and Kenwood brands, and somewhat more obscurely, also in kit form (as “Kencraft”). One variant of the latter I’ve seen on the web even had bright pink knobs and trim.

This receiver is fully solid state and receives AM, SSB and CW signals from 170 kHz to 30 MHz. FM is available through an optional board (QR-6FM). The RF amplifier and mixer stages both employ dual gate MOSFETs, which help minimise the cross-modulation effects that had plagued so many early 1970s solid state sets. The dual conversion design is another step in that direction. IF Filtering is via both mechanical and ceramic devices.

The spectrum coverage is split into 6 bands, and two dial drums indicate frequency; the uppermost for MHz ranges, and the lower for bandspread. The latter is calibrated more precisely for the amateur band ranges, though there was an optional SWL bandspread drum offered as an alternative. A 500 kHz crystal calibrator option was also available (QR-6MK). Mode is selected by a series of pushbutton switches, which have a very positive feel, and similarly either of the two bandwidths (nominally 5 kHz and 3 kHz, wide and narrow respectively). Rotary controls are employed for volume, RF gain, antenna trim and BFO pitch, and another pushbutton switches in the diode based ANL circuit.

The off-white plastic knobs, although well sized and comfortable, have a cheap look about them, which detracts from the overall aesthetics; something remedied on the R-300 to follow. There is provision for DC operation of the QR 666, but finding 8 “D” cell batteries in the drawer and removing the hatch where they are to be housed (at the base of the radio) means that this isn’t an attractive option. Happily there is also a separate input on the rear for 13.8V DC.

Antenna connections on the rear include screw terminals for high impedance, or 50 ohm SO-239. There is also a fold down rod antenna, which might prove handy, and a shorted remote plug which can be relay switched by a paired transmitter.

General performance is quite good, and in line with other serious sets of the era. This can be quite a lively receiver, though selectivity in the narrow bandwidth position can only be described as adequate. Drift is the biggest problem, and even after an hour of warm-up, one has to frequently tweak the frequency. For this reason, SSB and CW operation is hard work. At the time, Trio-Kenwood ascribed some of the instability issues to roughness during shipping and advised owners experiencing these symptoms to check the tightness of the screws holding the RF circuit board to the chassis. I doubt whether that advice helped many people!

Serviceability is very good, with easy access to all boards. The manual provides comprehensive disassembly instructions, a guide to re-stringing the dial cord, as well as the alignment procedure. I’m not aware of any particular intrinsic problems that are evidenced over time, though substitution of some semiconductors with modern equivalents may be required in the event of failure.

Examples of the QR 666 appear periodically on eBay and some radio enthusiast classified websites. Expect to pay AUD $120-$180 (USD $90-$135), depending on condition. Most are in pretty good shape cosmetically, courtesy of robust construction, though I’ve seen some with the front Perspex protecting the dial drums cracked. All in all, a good example of mid 70’s communications technology that has not yet quite made the “collectable” category, but is still devilishly useful!

Of course, Kenwood went onto greater achievement in the next decade with digital display receivers such as the R600, R1000, R2000 and R5000, all of which performed well, and it was a sad day indeed when the company finally left the general coverage receiver arena.

(This article first appeared in the September 2009 issue of the Australian DX News)

Once again, many thanks to Craig Seager for contributing this retro review to MEDXR.

Missed the other Retro Reviews? Check them all out by clicking below:

Retro Receiver Review # 1 - The DANSK RX4000

Retro Receiver Review # 2 - The HITACHI KH-3800W

Retro Receiver Review # 3 - The SCHAUB LORENZ ITT TOURING T104A RECEIVER

Retro Receiver Review # 4 - The RACAL RA6790/GM

Retro Receiver Review # 5 - The REALISTIC (RADIO SHACK) DX160

Retro Receiver Review # 6 - The KENWOOD QR 666

Retro Receiver Review # 7 - The RODHE & SCHWARZ EK890

Retro Receiver Review # 8 - The YAESU FR101S

Retro Receiver Review # 9 - The SELENA VEGA B206

Retro Receiver Review # 10 - The DRAKE SPR-4

Retro Receiver Review # 11 - The NATIONAL RF-5000

Retro Receiver Review # 12 - The YAESU FRG-100

Retro Receiver Review # 13 - The MARC NR-82 F1

Retro Receiver Review # 14 - The MURPHY B40

Retro Receiver Review # 15 - The STROMBERG CARLSON AWP-8

Retro Receiver Review # 16 - The YAESU FRG-7

Retro Receiver Review # 17 - The ALLIED/REALISTIC SX-190

Retro Receiver Review # 18 - The PANASONIC RF4800/4900 (DR-48/49)

Retro Receiver Review # 19 - The ZENITH TRANSOCEANIC B600

Retro Receiver Review # 20 - The SONY ICF-5900W

Retro Receiver Review # 21 - The KENWOOD R-5000