Re: Alternate pop fix...


Skip Davis
 

Allison try moving the FET to the M1/C51 side and mute the audio preamp directly that is where I have it and I’m not experiencing any detectable pop in my headphones. Having said that, your results may very. 

Skip Davis, NC9O 

On Jun 16, 2018, at 16:28, ajparent1/KB1GMX <kb1gmx@...> wrote:

While working with the uBitx V3 I finally got annoyed enough by the pop to fix it.
Basically copied from uBITX V4 but it still popped some..

Parts count 4:
2 1n4148/914 diodes.
1 10K resistor (any value from 10 to 100K really)
1 2n7000 mosfet

Why the second diode?  The TX line is relay switched 12V and relays are not instant
they take milliseconds to physically move contacts.  So the second diode to the T/R line
form the Raduino its the fast acting audio kill as that the command to the relay.  The
second diode resistor is the hold until the relay returns to RX position.

TX muting with no pop, no thump.  

Allison

schematic enclosed.
<IMG_1834.JPG>

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