This beautiful valve is a very early double grid valve. Space charge grid valves originated in Germany with the SS1. The design operated so that the first grid suppressed the space charge to improve sensitivity. Other Bi-grid designs were designed so that a signal and a local oscillator could be mixed together.

The construction still follows the coaxial pattern within a horizontal cylindrical anode, but the fixing supports have become more formalised, and thus the parameters more consistent. The second grid is also a wire helix, but with far fewer turns than the first grid.

The balloon envelope is 51 mm in diameter and, excluding the B4 base pins, is 88 mm tall.

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This exhibit was last updated on 28 August 2005