High frequency VOX. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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High frequency VOX. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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The operation of a portable VHF radio station in a car sometimes requires the prompt connection of a power amplifier (RA). In this case, it is desirable to minimize switching both when it is turned on and when it is turned off. A high frequency VOX can be used to solve this problem (see figure).

High frequency VOX

When the SB1 toggle switch is turned on ("QRO" mode), the supply voltage is supplied to VOX and RA. In transmission mode, the RF signal coming from the radio station is rectified by diodes VD1, VD2. The constant voltage of this rectifier opens the transistor VT1. Relay contacts K1 and K2 make the appropriate switching RA. When the toggle switch is open, the RF signal goes to the antenna bypassing the RA. Capacitor C1 is selected with the minimum capacitance at which VOX reliably operates.

Authors: V.Senko (UR5WG), G.Chliyants (UY5XE)

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