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QCX mini constant tone #qcxmini

 

Hi, I have the identical issue as described by people in this thread (constant 700 hz tone in the background) and was wondering what the recommended course of action was to fix it, since it is quite annoying. I'm inclined to believe it's not an issue with my soldering given the discussion in the prior thread. I did check my soldering just in case but didn't see any issues. I have PCB rev 2 if that's relevant. Thanks.
 

Thanks, Theo, for bringing this issue up again.? In February Hans acknowledged the matter and was going to look into it as soon as things settled down.? I've not seen or found any resolution as yet.

But in the thread you've so helpfully provided a link to, there're findings and suggestions by Mont Pierce KM6WT and Greg and me that point strongly to the source of the tone being the (next intended) Tx frequency signal at the Si5351 CLK2 pin out.? That might be checked further by removing the resistor in the path that feeds the CLK2 alignment signal to the antenna input. ? Mont and Greg (and maybe others) have suggested a firmware mod (move the Tx frequency well away from the Rx frequency during receive) as a fix.? If I'm right, removing that resistor (after alignment!) might also do the job.

I'm not going to mess with my mini any further - I very nearly killed it already with ham-fisted replacement of op amps!? (Hint: don't try that with lead-free solder)

73
Rod G0VKX
 

Sorry - thatt should've read Month KM6WT and Gregg W7GRM
 

I was never able to resolve this issue and still hear it on my mini. You can change the pitch of the tone by putting the mini into split mode and changing the separation of VFO A and VFO B as in the older thread. I was ultimately convinced that this tone can only be removed by a change in firmware such as Mont suggested (where Clk2 frequency is moved well away during receive, even if the output is not enabled):

  1. During receive (key-up)
    1. set Clk 2 off
    2. set Clk 2 frequency up 10MHz (or just off somewhere out of the way)
  2. During transmit (key-down)
    1. set Clk 2 back to transmit frequency
    2. set Clk 2 on
So there is no way around it but to hope for a firmware update some day where the tone is minimized.

73,
Gregg W7GRM

On Mon, Nov 8, 2021 at 4:17 AM Rod Smith via <rodjsmith=[email protected]> wrote:
Sorry - thatt should've read Month KM6WT and Gregg W7GRM

 

I get this constant tone as well. Will hope for a fix even though the mini is still usable.
73 de Arnie W8DU
 

Interestingly the tone seems to be much louder relative to the band noise when using headphones over a speaker. Perhaps the impedance of the audio device you have plugged in is effecting this? The radio is almost unusable when using headphones, but with a speaker I can barely tell a tone is there.
 

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Are you sure it¡¯s not an alignment issue? I don¡¯t hear any 700 Hz tone on my QCX Mini with headphones, earphones or powered speaker. It¡¯s just a quiet hiss. I get some noise when I use a switch-mode power source but it¡¯s very quiet on a battery.?

Regards

Ian


On 9 Nov 2021, at 5:47 am, Theo <theotheo36@...> wrote:

?Interestingly the tone seems to be much louder relative to the band noise when using headphones over a speaker. Perhaps the impedance of the audio device you have plugged in is effecting this? The radio is almost unusable when using headphones, but with a speaker I can barely tell a tone is there.

 

Definitely not an alignment issue. Just checked and it's all aligned correctly.

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