Hi folks. After trials and tribulation, I got the o'l bitx up and running. I adjusted the BFO and calibrated using local AM broadcast, audio sounds good. Except one thing. While adjusting the settings, I could hear the audio clearly, but there was a nasty tone coming over the intended signal. I posted about this previously, but I worded it oddly to sound like I was just hearing the AM carrier. To clarify that, I'm not hearing the carrier, I'm hearing the tone across the board, and it's pitch is NOT dependent on the VFO frequency. Oddly, the tone does change pitch and decreases in amplitude when switching from LSB to USB.

I have tried adjusting the BFO and calibration, but changing those to the point that the tone is inaudible renders the signal useless.

Could this be a tune up issue or something else?

Thanks to those more knowledgeable than myself that help out with problems :)

I work too with this problem, using stock firmware I don't have these tone, but upgrading to KD8CEC firmware, high frequency audio tone appear, louder that all voice band and give me headaches. I read a bit about this problem and seem replacing Arduino nano solve this problem.

But before do that, I make test and seem the CLK #1 is mixing probably with CPU clock.

Here my test with KD8CEC firmware:
-Audio tone at 8Khz very strong on LSB, nothing on USB.
-BFO frequency also move tone but audio was bad, so this is not a solution.
-ATT value also move to tone higher in frequency.

ATT = 0 mean strong audio tone at 8KHz
ATT = 10 Tone push to 13KHz
ATT = 40 Tone is pushed far away at 23Khz (if I remember well)

ATT setting shift the CLK #1 a bit to move signal on the slope of the 45MHz IF, but at ATT=40, radio signal seem strong as ATT=0 but high frequency tone is far away enough.

I also completly remove the CH340 from Arduino Nano because XTAL used by USB chip is a 12 MHz but this not affect tone at all.?

I try to replace nano or shift is xtal a bit using small cap to check if audio tone shift when I shift CPU clock source.

Remi, VE2YAG

Remi,?
I'll try out the CEC firmware. It looks like it should work with the stock display, correct? I have not explored the alternate firmware, I've only seen it used with the larger touchscreen display.?

Thanks!?

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