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Re: Trouble Oscillation qcx 40? #40m #alignment #problem #qcx40

 

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Gianpi, I think that the squeal starting when the frequency display starts means it needs the microprocessor to be in "operational mode". That means SI5351 started, and all the RX/TX voltages set to RX. Not sure if it will help with troubleshooting, but I will keep it in mind.

For our next trick, put C21 back and remove R29. That's our next break point, dividing the radio into two pieces again. If the squeal comes back, we need to look in the 700 hz bandpass filter area. If it stays gone, we are looking at the mixer or the sideband reject circuit.

73

Jim W4JED

On 6/15/22 19:20, info@... wrote:

Jim, I guess we have a small progress ! I have removed C21 and the loud tone is disappear...but nor completely...

Now If I put the volume to zero I am now able to listen the "white noise" typical of a radio without antenna, and when I increase the volume this is the matter: considering volume from o to 10, volume 0 = just white noise, volume 3 appear the tone but stll possible to hear the white noise in the background, volume 6 the tone is stronger, and still a white noise very weak, volume 9 just the tone.

I have noted that if I power on the QCX wearing the earphone, until the display show "5W CW TCVR 1.09 QRP Labs 2021" the tone is not present, as soon the dispaly show the frequency, the tone appear... is this a fact that help to understand further ?
Best 73 de IK1TTD Gianpi.?

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