CEI 901 and Nems-Clarke 1906

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CEI 901 front panel tuning dials tuners gear train block diagram
Nems-Clarke 1906 front panel tuning dials tuners gear train block diagram
CEI 901-1 receiver page Nems-Clarke 1906 receiver page

CEI 901-1

Nems-Clarke 1906

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Comparing the CEI 901 to the Nems Clarke 1906

The CEI 901 and the Nems-Clarke 1906 appear to be different generations of the same evolutionary line of surveillance receiver design. A close inspection of both radios shows many similarities. Both are 3-1/2 inches high with spiral dials and a gear train driving the dials, tuners and movable windows. The tuners are very similar in design and construction, using the unusual 7077 vacuum tube and Mallory Inductuners. They cover the essentially the same frequency ranges, with the same 21.4 MHz IF frequency, IF bandwidths (20 and 300 MHz) and conversion schemes. Carrier Operated Relay (COR), a squelch that could turn on tape recorders, was available on both receivers. A video and spectrum display unit (SDU) output was standard on both receivers.

The Nems-Clarke 1906 was a remarkable design for the mid 1950s. The CEI 901, which was probably designed in the late 1950s, takes many of the Nems 1906's ground breaking ideas and refines them. I suspect, though I have no proof, they shared design engineers, especially considering a number of key CEI technical and management staff came from Nems-Clarke.

One must remember these radios were made when the massively built Collins R-390 HF radios and Motorola R-220 VHF radio were newly designed and in production. Those Collins and Motorola designs were considered marvels of engineering. The CEI 901 and the Nems-Clarke 1906 radios represent a very different design philosophy from those heavyweights, but their performance was second to none.

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CEI 901-1 tuning dials

Nems-Clarke 1906 tuning dials

The tuning dials on both receivers are spiral plastic disks with moving windows. Both receivers use Raytheon knobs throughout, black on the Nems-Clarke radios and light gray on the CEI radios.

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CEI 901 tuners - low band (30-60 MHz) left, high band (60-300 MHz) right

Nems-Clarke 1906 tuners - low band (30-60 MHz), high band (60-260 MHz) right

The high band tuners in both receivers use 7077 vacuum tubes (two in the 901 and three in the 1906) and Mallory inductuners. The 901 uses all nuvistors in subsequent stages whereas the older 1906 used 7 pin glass tubes. The 901 low band tuner uses a Mallory Inductuner and nuvistors, whereas the older 1906 uses 7 & 9 pin glass tubes and a multi section capacitor.

More information on the 7077 vacuum tube - More pictures of the Mallory Inductuner

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CEI 901-1 tuning mechanism

Nems-Clarke 1906 tuning mechanism

The CEI 901 tuning mechanism has a similar layout and operation to the Nems 1906 and works just as smoothly but it is a simpler design.

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