Herman,
Well enough to use headphones comfortably and without the pop being noticbly loud. ?But like a lot of things if you're specifically looking for something its there as there are not that many absolutes. Also its been a while since Ive used the bitx40 and I have not compared results with the ubitx implementation.
Note the implementation is different as the PTT line is used as the control for the mute and it goes low for tx as opposed to the ubitx RX/TX line which goes high for TX. ?So an extra transistor is needed to invert the signal of the control line. But the principle is the same - put a mosfet across the volume pot to ground the signal with an RC circuit to delay turning it off at tx to rx transition to avoid the pop. Experiment with the rc values to get to what works.
On Bitx40 I made a small ugly style circuit on a piece of pcb as with extra transistor, point to point on the back of the pot was not an option. I think I added a small series resistor to stop some oscillations when vol was at max on receive. YMMV.
Note that this was not my idea. There is a post in the forum with a circuit diagram which I will locate and reference when I get home. Add a diode as seen in Hans Summers QCX mute circuit which is an enhancement.
73
Simon VK3ELH
