A Japanese R-392?
The above photos were from the Five Hundred Club web site, but are no longer available from the original source. This was a Japanese site dedicated to maritime communications. The page was translated by Tomohiro Inuzuka. Other information and pointers from Tom Marcotte and Leo Jormanainen.
Boatanchor afficianados in the U.S. and NATO countries are familiar with the Collins-designed receivers such as the R-392 and R-390A. They were produced by many companies for the U.S. military, and began entering the surplus market in the 1960's and 1970's. There did not appear to be any co-production by allied countries, nor any exact "knock-offs" from the the former Soviet Union or its allies. Then Tom Marcotte sent me a 1958 article (in Japanese!) by S. Shinagawa and T. Monoi, Communications Equipment Engineering Department, Tokyo Shibaura Electric Co (Toshiba). Subsequently, Leo Jormanainen pointed out the Five Hundred Club web site about the the same receiver.
Imagine, if you can, a "civilianized" R-392 with no power or main audio connections on the front panel. The row of controls directly below the S-meter on an R-392 has been moved below the tuning controls. Simpler power/function switch, small built in speaker, chrome rack handles on the front. S-meter with a white face, appears significantly larger than the 392's. Size is very similar, within 4 centimeters in all dimensions, but about 7.5 kilograms heavier. Power requirement (26 volts, 3 amp), sensitivity and audio output power are very close to the R-392 specs.
The tube/stage lineup is also very similar to the R-392. The RF and IF amplifiers are 26A6; the 1st and 2nd mixers are 26C6; VFO-Mixer is a 26D6; audio output is a 26A7-GT. Triple conversion from 400 KHz to 8 MHz, double conversion from 8 to 32 MHz. The calibration oscillator is followed by a multivibrator and harmonic distorter -- just like a R-392. But it is not an exact copy. The 3rd IF is 318 KHz instead of 455 KHz; there are 5 instead of 6 IF stages; there are 4 selectivity positions (6, 3, 1, and 0.3 KHz); the broader positions are L/C filters,while the narrowest is a crystal lattice filter; the 1st and 2nd crystal oscillators are 26A6 instead of 6AJ5; in fact, 26A6s are used in place of the 6AJ5 throughout the receiver, but the 12AU7s remain.
Two photos of the internals also show dramatic similarities to the R-392. The upper deck has crystal oscillator trimmers and a mechanical coil rack that any R-39X owner would recognize. The lower deck has the IF, AF, and calibration oscillator sub-chassis, along with the gap for the PTO.
The first version, the ZS-1447A, was produced in 1958. The ZS-1447H was produced in 1961.
It is difficult to imagine this receiver being produced and sold except under license from Collins. The similarities are many, the differences subtle. If you have any additional details about this receiver (or other non-U.S. R-39X clones), please send the information along.