Hi Jonathan.

I'm pretty much deaf, but even then I've not needed full volume. Raj's improvements to quality could even lessen the need. Given that, I've not needed any more than the pin3 mod - and isn't pin 6 the Vcc supply to U1? Are you sure you're not messing with pin 7? or 2?

You seem to have the CAD usable, how about this? - CW sidetone is possible by resistor (1k or so?) from pin 3, with another from there off to the raduino pin giving the tone. Audio in from the Volume control wiper is then to the 2N2222 collector point. The 2N2222 clamps the Rx audio on PTT - it should be pretty much instantaneous, and any 'pop' there will be from the remnant Rx audio level. Those 2 resistors are then a voltage divider? feeding the sidetone. U1 is, of course, powered on Rx, and the CW mod will have it powered also on TX - I don't operate CW so I haven't explored this. ON PTT release there may be some 'pop' as U1 powers up - it will only take a few milliseconds, and we can delay the 'let-up' of the 2N2222's clamp by a small cap across the (10k) resistor feeding its base. T=CR so ~10 milliseconds per microfarad.
In short, I'm wondering if there is any real need for that second 2N2222?

Hopefully helpfully,
73 de ZL2DEX

Hi Dexter,

Even with the Pin 3 mod, and also when I added the second 2N2222 to include the Pin 1 mod with it, I was having pops that were getting quite painful for a "non-deaf" person (hihi). Everyone's attempts seem to be trying to get the audio from the LM386 to be gone as quickly as possible. As the LM386 by default is disconnected from power on TX, I am using the second 2N2222 to slam the power off the chip as fast as possible.

I don't know what improvements that Raj has made/suggested of which you speak. I am not a huge fan of this "reflector style" forum, and find it confusing to browse and find that which you are seeking. If you could point me to a post for my review, that would be most helpful.

I do have CAD capabilities, but my post was created by simply editing the graphic that Giancarlo has kindly posted.

Let's talk about remainder of your last paragraph for a moment. I am assuming the CW mod you speak of is part of Raj's improvements. If it is not, are you suggesting I create a resistive audio mixer to patch in the output from the CWcarrier pin from the Raduino (Pin D6, or P3-2)? I assume that would be much nicer sounding than the square wave sidetone generated directly from the Rad to the speaker output as per Allards diagrams.

In any case, I would appreciate Raj's improvements to be pointed out to me so I can review and maybe regroup (always looking to improve).

Best Regards,

Jonathan, N?JMS

'pre-script' to the above:

I'm pretty much deaf, and have to use headphones to avoid deafening the rest of the household (or whatever environment), ...

:)

Hi Jonathan and all,

I see we are still on raf waters popping around the LM386. I am sorry I am not ready with the BITX to look at the real problem too.

If the POP is still present even with pin 3 to ground or trying fast discharge power to pin6 we may have only one spot creating this and it could be the push-pull circuit. To avoid this we should keep power to pin 6 all time and muting pin 1 as it controls the right differential, as I reported on trial 5a. This also should fix the TX to RX transition ... hope.

Thanks for the follow-up on the problem and 73

Gian
I7SWX

Hi Arv,
thanks for your comments and feedback.
How did you detect those capacitors being trouble?

73

Gian
I7SWX

Hi Arv,

Thanks a lot for the prompt reply.

I did not follow the BITX20 project so I did not knw about the problem and measurement you did and reported.
I guess the pulse was on the audio PA power line, right? You are right, it may be a complicated to find a solution.
I will try to think ... hi.

73

Gian
I7SWX

开云体育

Agreed - not easy to fix. However, should be easy enough to mask. Gian, your 2-transistor 'clamp', applied to U1 pin 3, takes care of Rx-Tx transition, and I'm working on Tx-Rx with 10uF (what's to hand) between +12 and junction of 10k/1N4148. If that 'hang' is not long enough (T=CR, uF*k = ms, 10*10=100ms - will that tenth of a second be too much? Lessee, have I got a smaller cap?) I'm sure the 10k could go to 47 or even 100k and still clamp effectively - do we really need (10V/10k=)1mA into either base? There's a couple of 150k still on that scrapped PC PSU .... We shall see ...
73

150k to the 2N2222 base (mine's a 2SC945, again from that PSU) from +12V works to mute the audio. That, of course, is with the base otherwise open (and collecting RF!). i'll try 10k base to emitter ... after tea :)
Meanwhile I note quite a bit of audio hiss - worsening with proximity to the board, and particularly bad by touching the filter xtal cans. Can they be earthed without altering the filter too much? Might give better RF immunity if, like me, your unit is 'al fresco' or in a non-shielding enclosure.

Too many bits and pieces lying around, and I think 12V from the PTT switch got into one of the Arduino pins and banjaxed it. I'd put the 10k B-E on the clamp transistor, but hadn't got to testing. Looks like a new Raduino needed. Display seems OK.
TTFN, 73!

What is the best mod for the click/pop. I would prefer a 1 transistor mod but looking for the best recommendation.
Mark
N7HWR