| Descripción |
According to Tyne, page 321, this first AC screen-grid tetrode, the UY224, later called 224 or 24' in the US was introduced in April 1929. It derived from the first US indirect heated triode UY227 from 1927 with the same heater-cathode combination. The oxide-coated filament operates at 2.5 volts AC or DC, taking 1.75 amperes.
With 180 volts on the anode (-1.5 inner control grid, 75 volts on screen grid) is resulting 4 milliamperes, the amplification factor is a bout 420, the anode impedance 400 000 ohms and the mutual conductance 1050 micromhos. Direct capacitance between anode and control grid is less than 0.01 picofarad which made Neutrodynes obsolete beginning in 1929.
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