ESM-ELINT receiver from the 1960s
Working on various vintages of equipment gives one a better appreciation for what we have today. Example - this is a frequency counter from the "HF Manual Receiver" which was part of a wideband surveillance receiving system that extended from VLF to microwave frequencies using a bank of front-ends to cover the range. It was designed as "ESM": Electronic Support Measures. These are gnerally passive systems that receive electromagnetic emissions from radiating devices.and are used to search, locate, and identify emitting sources for threat recognition, evaluation, avoidance, and targeting.
It's mission was ELINT, or ELectronic INTelligence, is the act of gathering intelligence through electronic emissions such as radars and radio intercepts. The WLR-6 was installed on some of the 637 Sturgeon-class nuclear-powered fast-attack submarines. The Sturgeon class (known colloquially in naval circles as the 637 class) was a class of submarines (SSN) in service with the United States Navy from the 1960s until 2004. They were the "workhorses" of the Navy's attack submarine fleet throughout much of the Cold War when ELINT activity was at it's peak. The boats were phased out in the 1990s and early 21st century, as their successors, the Los Angeles, followed by the Seawolf and Virginia-class boats, entered service. They have ELINT capabilty but with much more sophisticated (and classified!) systems.
The military designation for the HF Manual reeceiver is R-1451A, which is part of WLR-6(V) aka the "Water Boy 1" system.
I also have one of the VLF-LF receivers which is basically a repackaged version of one made by CEI, which later became W-J.
I've never even seen a picture of the whole system, but for whatever reason several HF Manual receivers have turned up at Chicago-area hamfests and I've latched onto every one I've seen. I now have three - two working (as of today) and one that's repairable. I think of them as a "transistorized R-390" becasue they cover the same range and have a similar bank of filters - .1, 1, 2, 4, 8, and 16 MHz - and both have digital readout tuning displays. But unlikes the R-390, a spin of the R-1451 knob will sent it zooming across the spectrum. These similarities probably shouldn't come as a surprise - if you were tasked to design a high performance HF receiver in the 1960s, what else would you model it after>
While other parts of the Water Boy system were repackaged commercial products, the HF manual receiver was designed by Sylvania Electronic Systems in the 1960s and use discrete transistors and early ICs. While I haven't made measurements, to the ear and finger they are very good, stable, selective receivers with a weighted flywheel dial that's fun to spin and very crisp and clear audio - probably the closest to SDR quality when fed into a good, amplifier and speaker. A bank of ceramic IF filters are provided and they are capable of ISB reception (using a separate pair of mechanical filters) and digital AFC. I've fixed several problems and fortunately was able to find a source for the complete technical manual, but considering the age of the radio, it's held up remarkably well and is plenty stable for copying SSB, CW, or even digital modes.
Each receiver of the WLR-6 system was a complete unit that slid into a mounting tray with mating connectors similar to those used on the mobile mounts for some high-end ham gear - even coaxial connections were made automatically when the radio was slid into position. IF outputs were made available for panadaptors or IF recording devices.
A good retro-technology lesson comes from the frequency counter module below that I recently worked on: