Jim / K7TXA
Eagle, ID

SKCC 10447T
BUG 301

I assume you wound T501 with the RWTST 3:2 turns ratio since you are running it at 12 volts.

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My opinion is you may show your numbers as long as you are within the QMX+ specifications as far as voltage goes. Be sure to confirm the accuracy of your measurement instruments. This should prove helpful to others.

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i could not see your plots either.

didn't see the plots but maybe i missed them?

Can you share your audicity recording from a QMX+ both with and without a signal with me?

Correction - Audicity not audaucity

Hi Yoon,

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Yes, besides erratic behaviors you described, the side tone also sounds funny.

Looks like to use reel wire to lower the SWR is the key. I could only get 1.8:1 from MFJ1720 as I remembered.?

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I will try on 10/12m again. If it works, it will be a good supplement to KH1.

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73

Wei AG6AQ

Matti,

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? ?I was recently working on adjusting the toroid winding for power adjustment when my QMX+ display screen flickered quicky while handling it.? I look to see what may have caused it when I noticed my power connection was coming loose from the back of the unit.? ?After pushing the plug back into place, the QMX+ quickly powered off instantly.? ?

? After that the QMX would not power back on.? ?I tried everything under the sun to get the unit to boot back up.? ?NO GO.

?What I found was that my Zener diode D109 had shorted to ground.? ? I could test this theory by pressing the power on knob and holding my finger on either Q109 or Q111.? ?I am sorry but I forget which it was of the two transistors but anyway the transistor got instantly hot to the touch of my finger.? ?I then pulled one of the legs up on D109 to take the diode out of the circuit.? After doing so I attempted to power on the QMZX+ with 7v limited to 200ma.? ?What did you know, the QMX+ came back to life.? ??

? I repaired the unit by replacing the D109 Zener diode with a known good one.? ? (D109= Zener 3.6v 500mW)

? I think this may be the issue you may be chasing for why your unit is not responding to the power on button if I am following the event of how yours shut down.? ?

Also, I remember check that the resistance across VDD and Ground read something like 265 ohms.? ?It should be in the Kilo Ohms or higher.? ?You can begin there with checking with your ohm meter.? No power applied occurs.?

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P.S? ?

?I agree that for the no power out issue, double check that you added the jumper during your build.? ?Good Luck and hope this helps.

On Fri, Feb 21, 2025 at 07:11 PM, Matti OH6BEX wrote:

But still, I do not understand how all this happened.

A full working equipment stops working by just pressing some buttons of the user interface.

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You applied pressure to the board.

Maybe caused something to short circuit.

Even under the board, you had it on the bench unmounted.

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73 Alan G4ZFQ

On Fri, Feb 21, 2025 at 08:11 PM, Matti OH6BEX wrote:

But still, I do not understand how all this happened.

A full working equipment stops working by just pressing some buttons of the user interface.

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Matti, hard to say without more information. Maybe after getting some results from your tests.

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73 Ludwig

I know people post pictures sometimes, but I cannot see them.

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I vassilate on whether my QMX+ is working correctly or not. I have never received strong CW or FT8 signals, but they are there - but weak.

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i have made audaucity recordings (low levels) both with a signal and not, which I would like to compare with others but cannot see any on Groupsio.

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i have looked for a setting which enables seeing pictures but no joy. I am using an Apple Ipad.

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Help!

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Hi Gert,

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Note that a minimum voltage drop is required.? From the specs:

Output adjustable from 1.25V to approximately 3V below the input voltage

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Three volts below 13.8 is 10.8 volts.? This would be the maximum output voltage regulated from a 13.8-volt supply.

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73

Evan

AC9TU

On Fri, Feb 21, 2025 at 11:49 AM, Wei AG6AQ wrote:

I was inspired by your post and tried myself with MFJ1720, the major problem is RFI. Have you seen RFI problem in your handheld setting?

Wei, what was the symptom of the RFI problem? Maybe some erratic behaviors of QMX like turning off itself or the keyer suddenly not working, etc.?

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I do remember having that kind of problems when trying handheld operation with different whip antennas and certain lengths of counterpoise wire. I think the problem can be generally minimized with the lowest SWR you can achieve, although there are many other factors affecting the antenna match with HT operation - your hand, head, body and your posture, also the dry or wet ground where you stand on, etc.

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Then I found it very handy to use the reel wire as the counterpoise, with which you can easily find the best match in any circumstances, which will surely minimize the RFI problem. I haven't had the problem with my whip antenna and the reel counterpoise wire.

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73,

Yoon KM6KJI

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Really Weird Twisted Sister Transformer.? This is the 12-volt version of the Wierd Twisted Sister Transformer for 9 volts.

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This is in the transformer manual introduction:

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73

Evan

AC9TU

What does the acronym 'RWTST' mean, or translate into?? Mr Google has not been helpful.

Hi Yoon,

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I was inspired by your post and tried myself with MFJ1720, the major problem is RFI. Have you seen RFI problem in your handheld setting?

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I can put battery in my pocket to reduce weight/volume and I agree ATU is not needed if you tune the antenna first.

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73,

Wei AG6AQ

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Elapsed time 3 days...

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--

Allison
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Post online only,?
direct email will go to a bit bucket.

It seems any photos attached to a thread are gone after a couple of weeks? So instead of posting my handheld QMX photos here again, I recommend you to visit my QRZ page to see how I'm operating QMX as HT -

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I have integrated it with the battery (3s1p 14500 li-ion cells with BMS), the internal speaker (though not much useful for noisy outdoor), and the plugin single lever cw paddle. For the whip antenna and the reel counterpoise wire combined with the QMX's built-in SWR bridge, I don't need an ATU.

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73,

Yoon KM6KJI