An indirectly heated, high slope, low noise triode, the A2521, especially suitable as an RF amplifier for use at frequencies in the region 500 to 1,000 MHz, has been developed by GEC.
The valve has a slope of 12 ma/V and an anode dissipation of 2.5 Watts. In normal receiver applications it is free from microphony. At 500 and 900 MHz the noise factors are 9 and 12 dB respectively.
When operating in a UHF grounded grid amplifier circuit, the power gain and bandwidth may be adjusted by altering the coupling between the anode line and the output loop. At 900 Mhz, for power gains of 6 and 16dB the available bandwidths are 80 and 4 MHz respectively.
From The Radio Constructor January, 1957.