Here's the story behind why Zenith and Central Electronics Companies have become such an important part of amateur radio history and the development of single sideband communications.
When Central Electronics was acquired by Zenith in November of 1958, it was a marriage of convenience. The last thing Wes Schum ever wanted to have happen was to lose control of the company he had founded through innovation, risk and hard work. Yet, the Central Electronics 100V transmitter, as revolutionary as it was, relied on the brain power, vision and wallets of two men: Schum and Batchelor. Its development was very expensive and the two were just about tapped out.
Wes insisted on developing the 100V through cash flow generated by his two bedrock products: the 10B and 20A exciters. Actual work on the 100V concept started in early1955. By the spring of 1958 they had one working prototype and were nearly broke. Development of the prototype took far longer than expected and now they were essentially “all dressed up with nowhere to go”. That is, they lacked the money to build the units in any quantity to yield a profit and they had fallen behind in paying 10B/20A suppliers.
Wes frantically searched for investors…the Borg Company and even Barkers and Williamson were considered. Eventually, the 100V prototype found its way into Karl Hassel’s ham shack. Karl, one of the founders of Zenith radio, was eager to embrace this new single sideband technology and making a line of high-end, premier amateur rigs intrigued him. So, in late 1958 a deal was struck.
With the financial depth and engineering talent of Zenith, it was then possible to produce the 100V, however, it wasn’t a walk in the park for even a behemoth like Zenith. Red ink continued to flow for nearly two years. So, although many decry Zenith’s abrupt decision to stop amateur radio production at Central, without their intervention there would have been no 100V, 200V or that one-off prototype 100R receiver. In actuality, Central Electronics continued on for five more years at a location in Paris, Illinois where home entertainment products and sub assemblies were constructed….absent of union involvement.
This Zenith Laboratories brochure illustrates the men behind the engineering divisions critical to Central Electronics. The 100R receiver was not actually a Schum-Batchelor design. Due to production delays and hiccups with the 100V and the later redesign of the 200V to improve production yield, development of the companion 100R receiver was transferred to Zenith’s Special Products and Military Division. That Division was headed by Ed Passow and his assistant was Bill Van Slyke, both of whom amateur radio enthusiasts and keenly interested in single sideband. It makes sense that the 100R development fell into their laps.
Now is a good time to inspect closely the Zenith Laboratories brochure for a time capsule surprise. Please note the photograph immediately below Bill Van Slyke’s. The person seated is Jim Clark who was the 100R’s assigned project leader. On the workbench in front of him is no other than a 100R prototype! The right hand of the chassis includes the IF and detector stages. The left hand of the chassis is reserved for RF, oscillator and mixer stages. The big cutout in the middle is space for the vfo, of course.
Look closely and note that there is no wiring on the left side of the 100R’s chassis, as at this point in time the 50KHz IF was getting Clark’s design attention. As one designs and later builds a receiver, you generally start from the speaker and work your way to the antenna connector and this is what Clark is doing here. The rack mountable test equipment that is partially shown above the right hand area of the 100R chassis is a Zenith-designed 50KHz sweep generator. It was designed as an engineering tool for swept response testing of the receiver’s 50KHz bandpass filter. How do I know so much about that sweep generator? Actually, it is because it currently resides, fully restored and operational, in my workshop!
I hope you enjoy this glimpse into the Zenith and Central Electronics Companies that have become such an important part of amateur radio history and the development of single sideband communications.