Audio Mute Kit

Audio Mute kit for Transceiver’s

PCB AND PARTS

The audio mute delay kit is been designed for Bitx builders, who may

be experiencing loud noise when Bitx PTT is pressed to transmit.

The Audio Mute circuit operates in the following way.

The 555 timer is connected to the PTT switch and generates a 100

msec pulse when PTT is engaged and another 100 msec pulse

when PTT is released.

The 555 timer is configured as a deb-ounce circuit, so contact

bounce of the PTT switch does not initiate any new pulses.

The output of the 555 timer and the PTT switch signal are combined

in logic to form two signals, a mute command and a transmit

command. The mute command turns on Q16 of the Exciter board

which shorts the audio signal to ground, and no sound is heard from

the speaker.