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Re: QMX Wish List


 

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Hans,

Thank you for your excellent explanation!? I wasn't worried about it at all, it was just a discovery as I was investigating CW works perfectly but digital was being squirrlly.? I've seen other comments about this but no one had a reason.? Just user error, as is typically the case.

Other than tweaking the low pass filters on a few bands, I have not much left to do on this QMX.? I have been on the air and made quite a few FT8 contacts with a little over 3 watts out, and some surprising CW contact.? The next challenge will be to try it out in a rapid-fire WWFF activation with a pile-up, but I'm beginning to think this might become a regular in my park activation line-up.? It's like a lot of things.? I worry a lot less about a $150 radio than gets the job done than my very expensive KX2 & KX3, and others in the cadre.? It cost less than my first QRP rig in 2011, and performs rings around that radio.

72

Charles - NK8O

On 1/13/25 10:29, Hans Summers via groups.io wrote:

Hello Charles

In addition, I discovered almost immediately that too much audio drive into the radio for digital modes will inhibit transmit.? I thought something was wrong with my QMX when it wouldn't transmit but for a brief second, but when I turned down the audio drive to 100% (Linux pavumixer) it behaved normally.? Presumably it can overwhelm the ADC.? The audio was turned up for another application but the laptop thought it applied to the QMX as well.

There is no ADC involved. All transfer from the PC to the QMX is digital via the USB audio sound card emulation of QMX. So what happens if you have a sinewave at full 100.0% volume, the sinewave peaks and troughs hit the peak numbers the digital transfer is capable of. If you go beyond that, then the peaks "wrap around" so you then get a frequency component at even harmonics, at a lower amplitude; QMX will then measure the incorrect frequency, as well as determine that the amplitude (of those wrapped peaks) is below the threshold and it will switch off the transmit.?

It's all correct behaviour of QMX.?

73 Hans G0UPL

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