To protect the MS5351M CLK0 output I added 4 Schmitt trigger buffers (at +5V DC) to get safe 50 Ohm +12dBm signal (5Vp-p square wave unterminated). I took the buffer circuit from the 10 MHz distributi

#vfo

Strange thing happened. I was measuring the VFO output signal spectrum at different frequencies. It is a VFO / SigGen using MS5351M. When I was changing the frequency from 150.000MHz up 1kHz it change

#vfo

Ron, I tried the factory reset a few times (resetting to TCXO each time). Interestingly, it moved the growl to different frequencies. I'll experiment some more tonight and try to discover any patterns

#17m #vfo #troubleshoot #qcxmini

Paul, go ahead and try the factory reset next. Be sure to reset the Reference Frequency to 25,000,000 since you have the TCXO. Ron

#17m #vfo #troubleshoot #qcxmini

I can confirm that by toggling the menu to "Speed" the growl disappears and I am able to hear signals that were previously obscured. This affects operation over the entire span of 17m. To reiterate, a

#17m #vfo #troubleshoot #qcxmini

Hi, Ron. I've not had a chance to do much of anything, even the reset. However, I did just discover that if I toggle the menu to "Speed" the growl disappears. I'm going to continue testing this across

#17m #vfo #troubleshoot #qcxmini

Paul, try the factory reset next if you haven’t already. If it’s still growling do the voltage measurements on all the opamps. That is a good way to zero in on a problem area. Ron

#17m #vfo #troubleshoot #qcxmini

Ron, et al. I ran the QCX-mini using a 9v battery and got the same results with regards to the "growling." So that confirms that it's internally generated. (Disconnecting antenna and key exacts no cha

#17m #vfo #troubleshoot #qcxmini

Paul, the microcontroller will go back to default settings on a factory reset. That’s all. So if it was calibrated before being reset you need to input the calibration data again. If it wasn’t calibra

#17m #vfo #troubleshoot #qcxmini

"...if one listens very carefully, the "growl" can be heard across the entire band, though at a level that would be negligible if that were only that, but it's not." That's a good suggestion, Ron. Whi

#17m #vfo #troubleshoot #qcxmini

Hi Paul. The first thing I would suggest is to change power supplies to verify you aren't getting the growl from that source. Even a 9 volt battery will power up the Mini for this test. Some power sup

#17m #vfo #troubleshoot #qcxmini

Hans et al. Having operated the QCX-mini 45 days or so (at the correct txco ref. freq., eliminating that variable - thanks, Hans) I have surely discovered what all the fuss is about with this little r

#17m #vfo #troubleshoot #qcxmini

Hans, Something else I just discovered is that the growling/engine idling sound that I hear across the band is also produced when keying in practice mode each time the paddle is depressed. Also, the c

#17m #vfo #troubleshoot #qcxmini

Hello there, Hans. Yes, I'm using the assigned value from the calibration sheet of 24.999.993 kHz. At this frequency the following occur: A consistent 700 Hz tone in the noise floor (low volume, but s

#17m #vfo #troubleshoot #qcxmini

Hi Paul So in that case, the reference frequency in menu 8.7 must definitely be 25,000,000 or within a few Hz of that; the value should be written on your calibration sheet. Another question, what pow

#17m #vfo #troubleshoot #qcxmini

Hans, Upon opening the unit the TXCO appears to be 25,000 kHz - it reads, "25.00 BN" and below it "D026". I can upload a photo if that helps. 73, Paul V7/KA4WPX

#17m #vfo #troubleshoot #qcxmini

Thanks for the clarification on that, Mike. That helps and is much appreciated. 73, Paul, V7/KA4WPX

#17m #vfo #troubleshoot #qcxmini

The board you mention is for uSDX if you choose. Hans does not support it other than provide the board. mike/w1mt

#17m #vfo #troubleshoot #qcxmini

Hi there, Hans. Yes, on the DVM front, so that makes sense. Understood. I will open up the unit and look for the TCXO. Upon opening the parcel, I noticed there was a very small, empty, PCB which looke

#17m #vfo #troubleshoot #qcxmini

Hi Paul We really need to know whether it has a TCXO in it or not. According to your order, it was supposed to have the 25MHz TCXO in it. However, the indications are that there may have been an error

#17m #vfo #troubleshoot #qcxmini