Hi-band kit: strong key-up popping clicking sound

[kg6yj]

Hello,

This is KG6YJ. I've assembled my Hi-band kit and did filter tuning by playing with the toroids. Compared to my Lo-band kit, the CW audio side-tone has very noticeable key-up (when I release the key) popping or clicking sound. When every 'dit' or 'dah' finishes, there's a strong popping/clicking sound in the side-tone audio, sounds like a DC in-rush. My Hi-band kit is at the latest Beta R2.00x firmware.

My Lo-band kit also has this issue, but much better and can be tolerated. It's at R2.00t firmware.

I tried to play with the audio signal path components: reducing C14 from 10uF to 1uF, adding a shunt 5.1K ohm resistor at U4 (ATmega328P) pin13 (PB1_AUDIO), adding a parallel 0.1uF capacitor to the original 10n (0.01uF) C37. It seems 20m band 'dit' key-up popping/clicking sound is getting better, but 'dah' key-up noise is still loud, and all other bands remain the same loud key-up popping/clicking sound for both 'dit' and 'dah'. At 15-18wpm, every 'dit' and 'dat' will give my earphone or the little speaker a strong 'pop' that is hard to tolerate.

FYI, I used a dummy load and another radio to listen to the CW signal from this Hi-band kit, the received CW signal sounds good, no key-up popping/clicking noise. That means the issue is at the side-tone audio section.

Question: right after the key-up moment, how the software/firmware control or release the pin13 (PB1_AUDIO) I/O port? Letting it floating to avoid DC in-rush (may be the best?), or making it pulled-up after a ramp, or making it pulled-down?

Tag R2.00i has "Fix CW key-up ramp issue", not sure if it's related.

Thanks Manuel and Guido for the great works!
73 de KG6YJ, Jun


ps. I get 4-5W output using 12V with displayed efficiency between 45% (10m band) - 58% (20m band), hopefully it's normal. I had to remove 1 or 2 turns from a few Lx1 and Lx2 toroids to get the desired 4-5W output power.

[pe1nnz]

Hi Jun,

Thanks for your feedback.
Question: are you observations done with semi-qsk ON? In This may reduce the clicking.

Currently during RX a PWM signal generates the audio, at TX this PWM signal stops and PB1 is kept as output, basically preventing in-rush current through speaker in case there would be no decoupling capacitor. I can see your point that this might cause a click as the capacitor will be discharged on the speaker. Will do a quick check to see if it helps to put PB1 as high-impedance (no output).

The remark in the change log was related to CW key clicks on TX, but this bug have been fixed.

[kg6yj]

Thank you, Guido. My observations were with semi-qsk OFF. If I change it to ON, the popping/clicking noise is totally gone, it becomes so quiet when I do CW TX. But I cannot hear any RX signal when I transmit dits and dahs until about 0.5 second after my last dit or dah, I'm a little nervous if I will miss anything because of that. But setting semi-qsk to ON may be a compromised work-around for now.

If you have a new Beta to set PB1 to high-Z, please let me know so that I can test it out.

Also I'm curious why the popping/clicking noise is more obvious on my Hi-band kit (main PCB 1.2) than my Lo-band kit (main PCB 1.0).

Best regards,
KG6YJ, Jun