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I just finished my QMX+ and thought I would share my RF power out readings. I did my best to wind all the torroids evenly though not perfect. Measurements are made with an Oak Hills QRP meter into 50 ohms, and with a LiPo supply voltage of 13.4 volts through a single diode. Voltage at the rig when keyed is just below 12 volts.

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73, Gary W8PU

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160 m - 5.9 w

?80 m - 5 w

?60 m - 3.9 w

?40 m - 3.9 w

?30 m - 3.7 w

?20 m - 3 w

?17 m - 2.3 w

?15 m - 4 w

?12 m - 2 w

?10 m - 3 w

?? 6 m - 2 w

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Congratulations Gary W8PU

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Likewise, recently completed QMX+.

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Likewise, applied my very best effort.

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Likewise, a good result.

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Terminal mode, supply 11.85VDC

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Diagnostics reported RF output:dumb load

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160M? 5.5W

? 80M? 5.1W

? 60M? 4.6W

? 40M? 4.0W

? 30M? 4.5W

? 20M? 3.2W

? 17M? 3.0W

? 15M? 4.5W

? 12M? 3.3W

? 10M? 4.1W

? ? 6M? 3.2W

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Very pleased.

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de Mike KM9D

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Congrats on the build! You should be able to get a bit more power out on some bands. I’ve built a few QMX and QMX+ at this point. Even the best windings need some tuning.?

I’ve found on the QMX+, with the vertical toroids, that my windings don’t need a lot of adjustment, but the start/end of the wire and how that is spaced with the bottom of the toroid affects my power. I’ve tinkered with them to get power up and it runs like a champ. Usually I use a plastic poke to move the wires so they aren’t quite as close or stay flatter to the toroid, but each winding is different. Spent some time on it and you’ll be happy with the results. I used an external watt meter, but the numbers were petty close to the internal one.

Mike and Andy,

?? I am very pleased with how the QMX+ turned out, it's quite an amazing transceiver especially for the price. I spent considerable time adjusting the spacing on the BP toroids and the posted results are the best I could come up with. Only 17m, 12m, and 6m fall below the expected 3 to 5 watt published specification. Optimizing 17 meters caused a drop in 15 meter output, so I settled for 15 meters. I am primarily a CW operator so I have yet to try the QMX+ on SSB.

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73, Gary W8PU

Looks similar to mine

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160	5.3
80	5
60	3.5
40	3.8
30	2.5
20	3
17	3.9
15	3.8
12	1.4
10	2.5
6	1.7

Not being able to leave well enough alone I took one last stab at tweaking the band pass toroids. The biggest change came with the 20/17/15 meter coils. I gave up a bit on 15m to increase power on 12m.? I suspect the correct method of adjusting the band pass coils would be to use a laptop and the QMX's built in utilities. I will save that for another day.

73, Gary

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160m - 5.6w

? 80m - 5w

? 60m - 4w

? 40m - 4w

? 30m - 4.1w

? 20m - 3w

? 17m - 2.8w

? 15m - 3.8w

? 12m - 2w

? 10m - 3.2w

??? 6m - 2w

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On Tue, May 27, 2025 at 11:33 AM, gary poland wrote:

tweaking the band pass toroids.

I think you mean Low Pass Filter toroids.? Changing the bandpass toroids will primarily affect receive sensitivity.? ?Adjusting LPF toroids will primarily affect output power and harmonic rejection.

Stan KC7XE.?

Stan,

? I initial tried tweaking the LP filters with little effect. They are tightly wound and because of the tap little movement is possible. So yes I played with the spacing of the windings of the band pass filters. Most are completely spread across the entire toroid, no turns were added or removed.

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73, Gary

On Tue, May 27, 2025 at 01:37 PM, gary poland wrote:

I initial tried tweaking the LP filters with little effect. They are tightly wound and because of the tap little movement is possible. So yes I played with the spacing of the windings of the band pass filters. Most are completely spread across the entire toroid, no turns were added or removed.

Gary, maybe we just have a different understanding of LPF vs BPF.? On QMX/QMX+ only the bandpass filters have taps.? The low pass filter toroids (vertically mounted on QMX+) do not have taps.

Stan,

?? You are correct, I have the terminology of the two swapped.

Thanks, Gary

Thanks for insight and encouragement.

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Conclusion, I can learn much from Michael Faraday, Joseph Henry, and from those who followed.

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Gary, checking band configuration table, 12M & 15M do NOT share a filter.? I may have misunderstood your reported observation.? Now, I'm guessing you let 15M stand and turned your attention to 12M.

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Andy, I intend give more attention to detail, later.? I expect to find a way to make 4-watts for 20M.? I'm located in Malaysia and the tool at hand is often a bamboo-skewer.? You can probably imagine.

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Stan, thanks for the support of your knowledge and experience.? I've noticed, your contributions to the group are immense.

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73 all es gud DX

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I have a QMX+ (kit) that I completed a couple of months ago.? It is board revision 2, firmware version 1_00_027,? and it’s wired for 12 operation RWTST output transformer.? I’m powering it with a Drok buck converter.? The voltage is adjusted to deliver 11 volts at the radio’s power connector (measured during transmit).

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After correcting some “stupid” mistakes (yep- guilty of missing that jumper that connects the antenna BNC to the rest of the circuit), I’ve been using it since the beginning of this month.? So far I’ve confirmed 28 states and 13 countries (mostly FT8, but some CW too), and I've made contacts on every band (except for 160).? It’s been fun!? I’ve been following this thread and enjoying learning more about this radio, but I’m a bit concerned about my power output.

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The response of all of the LP filters ranges from 0 to +4 (dB?) at the center frequency for each band.? The curves seem to look “normal” to me.

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The radio is drawing .15 amps on receive, and the XMIT currents below are calculated by subtracting this 150ma from the buck converter’s current display during transmit.? It was transmitting into a dummy load, and the tests were run using the terminal mode’s diagnostic screen.? The Output Power was as displayed on the diagnostic screen (and the readings pretty much agreed with my external wattmeter).

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The Supply Voltage displayed on the screen was about 10.9 volts and the displayed Transmit voltage for each band was between 9.2 to 9.5 volts.

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I think that about covers all of the measurement details.? Here’s what I measured for each band:

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BAND	XMIT CURRENT (AMPS)	OUTPUT POWER (WATTS)
160	.91	5.6
80	.59	4.4
60	.42	3.1
40	.38	3.0
30	.42	3.2
20	.44	3.0
17	.84	3.2
15	.46	2.9
12	.90	3.3
10	.64	2.9
6	.43	1.6

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Hopefully this data is useful for anyone else trying to get their QMX+ to work properly, but I do have a few questions:

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The output power on several of the bands seems to be a bit lower than other results that I’ve seen posted.? Is there any indication that something’s wrong?? Should I be getting more power? If so, any suggestions on how to squeeze out another 500 mW or so?

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When you “tweak” the LP filters, what are you measuring and how are you doing it?? Is it just a trial and error process of trying to maximize power at the frequency of interest or are you using the filter scan to tune the “cutoff” frequency so that it’s further above the frequency of interest??

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And… why is the supply current draw for 12 meters (.9A) so much higher than the other bands even though the output power isn’t much higher?

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Thanks much,

Larry

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I was studying pages in the WIKI and noted the following remark:

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"Sweeps using TX mode may use a bit more current than normal transmitting."

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Larry, keen observation.

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I do notice that 12M & 17M are NOT so different from each other.

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Good luck

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I found that tuning with a power meter is better than using the low pass filter traces in diagnostics. Simply put, the scale and resolution of the graph are good to have a rough idea of performance, but not detailed enough for tuning.

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My tuning method is to attach the radio to an external power meter and then a dummy load. I have a variable power supply and I set it for 9 volts for my 12 volt build to lessen the power. I go key down and adjust the spacings on the low pass filter for max power on a band. Since most filters cover multiple bands, I cycle though all the bands affected by that filter to balance output between them or set it to favor the band I prefer.?

My approach to actually turning the coils is to start by checking the spacing between the PCB and the toroid and make sure those wires aren’t crossed or all over. That is a quick way to lose power. If it’s bad, I get out the soldering iron and try pulling it tighter while melting the connection. After that I start spreading and bunching the coils on the toroid as a whole. Once I get max power from that approach, I try doing that again on the second toroid. Once both have max power, I will some times tinker with moving single or small groups of coils to fine turn the inductance. Usually this isn’t necessary. Since I take mine portable a lot, once I have everything happy, I use hot glue to hold things in place so it won’t move in transport.?

I’m currently on the road and just have my QMX with me right now so I can’t share my power output, but all bands are roughly 4 to 5 with 160 and 6 meters being outliers (160 high and 6 meters low).?

On Wed, May 28, 2025 at 08:16 PM, Larry- WA2VKG wrote:

The output power on several of the bands seems to be a bit lower than other results that I’ve seen posted.? Is there any indication that something’s wrong?? Should I be getting more power?

Some bands share a lowpass filter and their adjustment will trade off power between them. You can pick up one band but another may suffer.

Having tested several ham-grade power meters against my Keysight power sensor/meter and seen errors as high as +/-20%, it is possible that the difference their results and yours? is measurement error.

Other possibilities are different operating voltages; some folks' "12V" is closer to 13.8V, which will affect power output.??

Your results look like they are comparable to others'. The station at the other end will never know the difference.

Remember,?

"If you compare yourself with others, you may become vain or bitter..." Max Ehrmann

73, Don N2VGU

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