This is an example of the real thing. Radio Engineering Labs was a long-time collaborator and supplier for Armstrong. The earliest FM programing relay stations used REL equipment. And you note by the licensing logo, this unit has the full Armstrong circuitry - not that "Super-FM" that RCA was licensing. Armstrong's associate Runyon exercised his option to buy REL in 1942. Too bad it's so expensive - $349 plus shipping at this writing.

I would assume that it has only the 'old' FM band?

That thing is a monster!!!
There is 17 tube in the thing!!!

http://www.nostalgiaair.org/PagesByModel/057/M0016057.pdf

Several of the tube types peg it as definitely postwar.

The REL Precedent FM tuner is perhaps the most outrageous FM tuner ever made. They always go for megabucks on the rare occasions that they appear. It's from the early 50's and has miniature tubes.

This thing has loctals. Is it a tuner? I dont see a speaker. Maybe a broadcast monitor?

John

That set features both the old and new FM bands. Looking at the schematic of the amplifier I see it has negative feedback so the sound quality should be very good. It’s not an attractive radio since they were mostly used as station monitors, but once properly restored, it should perform great. At least it’ll be able to tune in music stations on the FM band unlike the AM band today whose stations basically spew out nothing but news, talk, religion, and sports. I’m sure some audiophile will snap it up for top dollar.

Michael Feldt

You're kiddin' me! Here's another one - and at only $225!

Yeah, and it is a parts radio at that!

The REL receiver pictured appears to be a typical example of what one looks like after many years of abuse and lack of loving care. While a few went into private homes and a few specimens may exist in pristine condition, this is what happens to gear after it's been knocked around at a radio station which is where many of these units were placed. The REL decal below the dial is of course not original and the decorative chrome strips on either side of the cabinet are missing.

The 646 was available as both a rack-mounted version though seen more commonly in the metal case. Three versions are shown in the factory service manual. The 646-B was a complete a/c-operated receiver with a 10-watt push-pull output stage. The 647-B was a tuner designed to operate into a 600-ohm load. The 648-B was a field/mobile 6-volt receiver requiring a separate B-voltage supply offering an audio output of 4-watts into a 6-ohm load.

The 646 series was REL's post-war successor to the pre-war [1939-41] type 517-A, a two-dial 42-50 mc superheterodyne that did not have ganged tuning but strictly followed Armstrong's circuitry as REL was one of his original licensees [General Electric and Stromberg-Carlson were among his others].

There were several iterations of the 646 series. The first units manufactured through 1948 covered both the prewar band [my unit covers 44-50 mc; curiously omitting 42-44 mc] and the present 100-channel 88.1-107.9 megacycle band.

After much debate and contentiousness between the FCC vs. Armstrong and his followers relative to retaining a portion of the old 45-megacycle band for relay purposes, the Commission ordered the closure of all low-band facilities by December 31, 1948.

Thus, later versions of the 646-series covered only the 88-108 mc band and the REL's lower dial scale substituted channel numbers (201-300) for the 44-50 megacycle calibration.

The 646-B remains an excellent FM tuner/receiver in what could be described as a "supertuner" of its day but it wasn't the only one. A firm even more obscure than Long Island-based REL -- Harvey Radio Labs of Cambridge, Mass. -- manufactured a limited number of model 193-R FM monitor receivers which out-class as well as out-weigh the much touted 646 series.

The 646-B is quite sensitive and has a smooth tuning "feel" across the dial. It's only moderately selective but the two meters [signal strength and center-channel tuning] are a classy touch. Of course, I would strongly recommend replacing every bypass capacitor.

Incidentally, the eBay "parts" set is missing its power transformer; a suitable substitute shouldn't be hard to find.

In 1950-1, REL took out small trade publication ads to announce the final 646 production run though with plans for a successor that turned out to be the "Precedent" or model 646-C. When the much-anticipated "Precedent" finally appeared in 1954, it wasn't too long after Armstrong's suicide [1-31/2-1-54] and the closure of his station, KE2XCC [93.1 mc/Alpine, N.J.] on March 5, 1954 when FM broadcasting in this country really was at its nadir. As an aside, both the military and prospective television broadcasters were screaming for FM's frequencies as late as 1956-7 but the FCC held fast and by that time, FM broadcasting was beginning its resurgence.

While there's been much whoop-de-doo about the "Precedent" over the years, I find its performance somewhat disappointing and echoing the comments found in a comprehensive review of "state-of-the art" FM tuners published by Consumers Research [Washington, N.J., NOT Consumers Union ("Consumer Reports") which at the time was based in Mount Vernon, N.Y.] in 1956.

The "Precedent" is very sensitive of course but its front-end is easily overloaded which is why there's a multi-level attenuation control on the front panel, something also found -- but seemingly less necessary -- on the 646-series. Selectivity is also only fair though there's no argument about the "Precedent's" appearence, tuning "feel" and perhaps audio performance though who can tell these days the way most FM stations over-process their signals.

The "Precedent" thoughfully included a multiplex output jack indicating an awareness of the earliest binaural (multiplex) tests that began experimentally in 1950 at New York's WGYN/97.9.

I have connected such well-known multiplex adaptors as the Scott 335 and the Fisher MPX-100 to this jack and the audio quality is surprisingly good. Adaptors such as these remain highly collectible fetching what seem to be outlandish prices though in truth their output tends to be noisy except in the strongest signal areas.

The dark-horse of "super-tuners" remains the National NC-1000, "Criterion" binaural AM-FM tuner introduced in 1954. "Consumer's Research" gave the "Criterion" a very favorable review though it scolding the National for its relatively tiny dial which is a point well taken.

I will go further. The NC-1000 is just as sensitive as the "Precedent" and much more selective based on my field tests. The "Criterion" shows up from time to time at hamfests, etc. but remains un-recognized and largely ignored even though it is a superior performer.

Thank you, al germond, for that truly enlightening post!