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Hi
I just had another session with my new QMX and loving it more and more.? I've decided it is the only radio I need to take on holiday.? I'm normally torn between both QCXs, but I've made a two bander covering 40 and 20 m so I could reduce it to one.? MCHF- it feels a bit fragile and draws a lot of current, eats my battery pack in less than an hour so realistically you need to carry a spare battery and I haven't got one.? KX3- a bit heavy and I worry about the cost of anything happening to it, its advantage is it is one of the best cw radios in the world and it lasts for ages and ages on its internal batteries.? I normally end up taking my KX3 and so far I haven't lost or damaged it, but I worry.? It is a good benchmark against which to judge other radios though.??

Within the limitations of what I want a radio to do, the QMX does probably 90% of what the KX3 can do.? The extra 10% is for competition or serious dx and to be honest I don't do much of that, particularly on holiday!? Its mostly to do with receiver sensitivity, crystal roofing filters and a vast array of DSP options and electronic filtering that enables a KX3 to pull out a barely detectable signal even with a kw transmitter contesting on the same band in the next room.? I probably miss out on some of its performance anyway because I don't know what all the controls do or how to use them.

The QMX CW filtering is fine, its a good compromise, its wide and shallow enough that you can easily tune the band and hear what's there yet is narrow and steep enough to have a QSO on a reasonably busy band without being distracted by qrm.? I'd like some control over it to adjust between 100 and 1000 Hz and to offset the centre frequency to skew the shape of the filter.? I like a fairly wide filter and only close it or manipulate it when I need to.? Filtering on the QMX should be a firmware thing and it may eventually come, but I don't mind if it stays as it is now, its perfectly good enough.? ?

I was using my 12v battery pack this evening so it was putting out about 5 watts or fractionally over on 40m.? It survived a three or four second burst of auto ATU (Elecraft T1)? and I could hear signals from UK, Ireland, France, Spain.? I never had to call CQ but just answered calls, everyone I called heard me and I was getting good signal reports.? I also had an email follow up from one op commenting on how nice the QMX sounded.? All contacts made so far have been qrp/qrp and in England, Ireland and Spain.? After three back to back cw qso's over about half an hour it was warm to the touch but no more.

So I'll take my QMX on holiday, I'll leave my KX3 at home and I don't think I'll miss it.??

Brilliant radio, thanks Hans!

73/72 all?

Peter?

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I set up a rule in my email client that automatically deletes emails from N4QA so now all I get is the moaning.

Chris, G5CTH

Aiaaah !
72,
Bill, N4QA

Two minutes to respond ...not Korsakoff Syndrome ....just a simple Troll... are we having fun?
Dave VE3KCL

Gee, I can't remember !
72,
Bill, N4QA

I have always wondered if extended use of FT8 can contribute to Korsakoff Syndrome.
Dave VE3KCL

Tnx QSO, WB8UBR.
72,
Bill, N4QA

Wow now I feel like a jerk, I thought I had read the manual in detail but this was already covered! Or I read it and somehow felt like there was enough room at the time - I did end up having to swap mine out for a second encoder (harvested from a previously botched QCX-mini) after first assembly because the pushbutton on the encoder I got was jammed (or so I thought - I later revived it with some excessive force)

Thanks pointing that out.

73
Andrew KI7FXL

Thank you for taking the time to reply Hans.

73, Kevin NZ1I?

Thanks for the reassurance Hans.? I'll crack on with building and testing.

I finished my QMX build today and thanks to the note in the assembly manual I found the same issue during continuity tests before powering up for the first time .

"3. Check that there is no short-circuit between the body of the left rotary encoder, and the DC input jack power connector."

It wasn't obvious at first but applying slight pressure with the DVM probes was enough to register a short circuit.? So I insulated the rear of the DC jack, powered up initially at 7.5v with the current limiter set to 250mA and all appeared good.? I then increased the supply to 12v and loaded the firmware successfully and hey presto the QMX is working as advertised!

73 Chris 2E0IFA

Cliff and Matt, thanks for the ideas. Looks like 10 V will work just fine. Thanks. 73, Mitch NK3H

Hello Hans,

Of course, this was only a test, not a permanent solution.

My second kit arrived today. I quickly swapped the power board and the rig came to life immediately. I did the sensitivity modification #2. Although the rf sweeps look way off, RX was fine.



Remains to find out, what the issue with the first power board is...

Best 73s
Simon

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I also destroyed my BS170 2 times. Also the 74ACT08. Reduced the Voltage to 10V.now I got 3-4 Watts.

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Mitch,

Thanks Cliff. I replaced all four. At 11 VDC the unit is putting out 5 w into a dummy load on the meter, 47 V p-p on the 'scope and 860 mA on the power supply. The BS170 leads are warm to the touch. Not hot. But at 11.5 VDC, they're almost too hot to touch at the end of the 13 sec FT8 transmit. The unit is outputting 6 w on the meter, 50 V p-p and 950 mA. Should the transistors be so hot? The unit is designed for 12 V but I don't know how they'd survive at the voltage. And I'm sure WSPR would knock them dead--well, I'm not sure but I don't want to try. What could be the cause of too much power output? I don't get it. Any help would be appreciated. Thanks. 73, Mitch NK3H

oops, make that 40m QRPppp !
72,
Bill, N4QA

Tnx QSO, KN4AME
72,
Bill, N4QA