| 摘要 |
The automatic gain-control devices for conventional receivers have a long holding time constant C3 which fixes the gain-control voltage Vg when the signal to be monitored Sa drops suddenly and steeply; this makes it possible to preserve the control voltage during speech blanks. However, when the receiver is of frequency-evasion type, if a channel with a very strong signal is received, the receiver is desensitised, for the duration of the holding constant, since the gain has too small a value for the following channels if their signal is not also very strong; in order to avoid this the amplification at the start of any new channel is carried out with the aid of an average control voltage obtained by memorisation and integration 4 over a time markedly greater than the duration of reception of a channel. Application to frequency-evasion SSB receivers. <IMAGE>
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