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UHF receiving valves for Bands IV and V are now coming on to the market - colour television and mobile radio being two likely future applications. One might expect such valves to look rather unusual. In fact they are just like conventional B7G and B9A miniature types, except for the planar type of electrode structure inside. A recent one from GEC is the A2521, a low-noise triode suitable for use as an RF amplifier in the 500-1,000 MHz region. Its slope is notably high at 12 mA/V, and the noise factor varies between 9 and 12dB, depending on the frequency.
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