Re: I7SWX PTT Pop Mute


Hi Jerry,

I recently added the tx mod to my latest Bitx40 (3rd).  So far of all the tx pop mods, this one has produced the best results. 

The noise i refer to is a screech or loud click / pop when tx is turned on.
I tried the ctt which used a 2n3904 and a 2n7000fet - it worked but would occasionally cause a tx hang.

My best results, which remove nearly all the noise is the circuit above and the add on relay.
The relay mod uses a new relay and a  set of contacts which open the speaker when tx is activated.

I use the voltage from the led rx/tx mod... I just tapped in to the red led - when it goes red it keys my relay.
I found by using both mods it cut the pop dramatically on both when keying and unkeying the tx.

The outgoing carrier noise is not affected...


On Wed, Jul 26, 2017 at 3:53 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

Please tell us a bit more about what you figured out.

Does this cure the pop in the headphones when you press PTT? 
What I would call "tx noise" is the brief outgoing carrier, which is a totally different issue.
If this fix addresses the outgoing carrier issue, please show us where to find the fix.
What other circuits did you try?
In what way did this solution work better?
What is the relay mod?

A full description of what you did would be helpful to many here.


On Wed, Jul 26, 2017 at 11:32 am, Joe wrote:
I also tried your circuit for the tx noise.
It works very well.
I have tried several but this had the best results.
I use it in conjunction with a relay mod.

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