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For pentodes, it is higher, about (5-7)/g m. Valves with high g m thus tend to have lower noise at high frequencies. In the audio frequency range (below 1–100 kHz), "1/f" noise becomes dominant, which rises like 1/f. Thus, valves with low noise at high frequency do not necessarily have low noise in the audio frequency range.
A valve can contain more than one control grid. The hexode contains two such grids, one for a received signal and one for the signal from a local oscillator. The valve's inherent non-linearity causes not only both original signals to appear in the anode circuit, but also the sum and difference of those signals.
Class IV valves have no more than 0.01% leakage under those conditions; this tends to require multiple graphite piston rings or a single Teflon piston ring, and lapped metal seats. Class V valves leak less than 5 × 10 −12 cubic metres, per second, per bar of pressure differential, per millimetre of port diameter, of water when tested at the ...
6N3C power tube. A valve amplifier or tube amplifier is a type of electronic amplifier that uses vacuum tubes to increase the amplitude or power of a signal.Low to medium power valve amplifiers for frequencies below the microwaves were largely replaced by solid state amplifiers in the 1960s and 1970s.
The higher the resistor the greater the gain, the lower the damping effect and the greater the risk of instability. With this type of stage good layout is less vital. Passive grid design is ideal for audio equipment, because audio equipment must be more broadband than RF equipment. A RF device might be required to operate over the range 144 to ...
Valves continue to be used in some high-power, high-frequency amplifiers used for short wave broadcasting, VHF and UHF TV and (VHF) FM radio, also in existing "radar, countermeasures equipment, or communications equipment" [7] using specially designed valves, such as the klystron, gyrotron, traveling-wave tube, and crossed-field amplifier ...
The pentagrid converter is a type of radio receiving valve (vacuum tube) with five grids used as the frequency mixer stage of a superheterodyne radio receiver. The pentagrid was part of a line of development of valves that were able to take an incoming RF signal and change its frequency to a fixed intermediate frequency , which was then ...
The Fourier transform of a function of time, s(t), is a complex-valued function of frequency, S(f), often referred to as a frequency spectrum.Any linear time-invariant operation on s(t) produces a new spectrum of the form H(f)•S(f), which changes the relative magnitudes and/or angles of the non-zero values of S(f).