Re: BITX40: Delay of PTT, RX amp keeps active too long
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A few possibilities: Swap ?pins 3 and 5 of relay K2, add a 100k resistor from K2-1 to ground. ? The resistor slows down the falling edge there to avoid a pop in the speaker, the 100k should discharge the 1uF at C115 with an RC of about 1/10 second.
Reduce the size of the 470uF cap at C110. ?Perhaps 47uF is sufficient if you use headphones with the volume set fairly low.
Add an NFET or NPN transistor with an appropriate load resistor to quickly discharge C110 when the TX rail is high. ?If you have some spare IRF510's lying about to replace the final when it blows, add one in there with the gate tied to the TX 12v rail, the drain tied to the top of C110, and the source to ground through a 100 ohm resistor.
Haven't tried any of these, as I don't yet have a Bitx40.
Jerry, KE7ER ---In BITX20@..., <ronvandoremalen@...> wrote : Experience a long PTT switch over time, resulting in a extended RX audio.
Ashhar mentioned this probably is caused by the large uF in the audio amp circuit ?
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