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I have just finished building a Rev 2 QMX+. It was a fun build and all went smoothly ... with a couple of minor exceptions.

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1) For some reason, PuTTY refused to work on my Win10 desktop (it had worked in the past). It recognized the QMX on a serial port but then it just "hung". Luckily, my Win11 laptop worked perfectly and I moved on to the diagnostics.

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2) Power out ranged from a high of 5.0 watts on 160 to 2.3W on 6 metres. (This is quite acceptable for sure.)

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3) The biggest problem was the image rejection on 160M. Here's a table of the results:

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Band????? Image

160????????? -3.8 (no the decimal point is correct!)

? 80????????? -37

? 60????????? -41

? 40????????? -43

? 30????????? -46

? 20????????? -50

? 17????????? -58

? 15????????? -36

? 12????????? -35

? 10 ? ?????? -38

??? 6????????? -20

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In an effort to resolve the 160M image problem I removed L401 and rewound it! Unfortunately nothing changed. I also went into the band configuration and changed the BPF from 0 to 1 just to see what happened. Nothing changed? So it looks like BPF 0 is not there for some reason?

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The chances of me using this rig on 160 with 2.3W are fairly remote, however, it would be nice to get the image numbers to a more reasonable level.

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Thoughts appreciated. Thanks!

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73, Rick
VE7TK

Website:

Many thanks Alan!!

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After all those toroids I REALLY needed more practice with 44 turns of #28 wire on a T50-2 core! Hi!!

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73, Rick
VE7TK

Website:

Here are my output values by band. I did a little squeezing and expanding with the Low Pass Filters but didn't gain much. I'm not sure if these are typical or not.

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73, Rick
VE7TK

Website:

Those output powers you listed, are very close to my QMX+ build as well. ?Looks normal to me. ?I've worked the world on this rig already!

VE7SRF

I completed a QMX+ last week and the output powers are very similar to yours as you can see below. Measured power is from an external power meter and reported power is from the diagnostic menu on the rig.

One thing I noted was that the 10m output using the diagnostic tab is lower (and the power meter confirms) than that measured just keying the rig, I'm not sure if that is a feature or a setting I've messed up somewhere.

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QMX+ Measurements	12V	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?
Freqy (MHz)	1.8	2	3.5	4	5.332	5.405	7	7.3	10.1	10.15	14	14.35	18.068	18.168	21	21.45	24.89	24.99	28	29.7	50	54
Power Measured (W)	6	6	4.8	4.6	4.8	4.8	4.8	4.8	5.5	5.5	3.8	3.5	3	3	5.2	5.2	3.5	3.5	4	4	2	2
?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?	?
Current (A)	0.95	0.95	0.6	0.6	0.6	0.6	0.6	0.6	0.75	0.75	0.5	0.5	0.75	0.75	0.9	0.9	1	1	0.7	0.7	0.6	0.6
VSWR	?	1	?	1	?	1	?	1	?	1	?	1.1	?	1.1	?	1.1	?	1.1	?	1.2	1.25	?
Reported Power	?	5.8	?	4.3	?	4.2	?	4	?	5.1	?	3.3	?	2.9	?	4.4	?	3.2	?	1.2	2.3	?
Volts TX	?	9.8	?	9.8	?	9.8	?	9.8	?	9.8	?	9.8	?	9.8	?	9.8	?	9.8	?	9.8	9.8	?

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G0TXL (Paul)

Thanks Paul! What jumps out at me is that on 12m your output power is low and current pull is high. That sounds similar to my QDX situation on 10m. Do you find your finals overheat on 12m? Naively it appears to me you're over the rated dissipation for that band.

I haven't really run the rig for long other than quick cw tests, nothing seems to get warm. The current values were taken from the psu and are of dubious accuracy but should give a relative indication. The QMX+ broke down yesterday and I've only just got it going again (zener diode failure). I put the lower power down to the LPF compromise; looking at the diagnostics its not really optimised for that band, could be the amp is therefore running into an odd impedance.? But its speculation without doing some measurements. Its producing the power specified with the exception of 6m which I suspect is normal from other results I've seen on the forum; including those from Rick below.

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G0TXL (Paul)

Getting T501 to deliver power from 1.8mhz to 50mhz is well beyond anything I'd attempt.

Amazing 6m works at all.

Variations between rigs with hand wound inductors is to be expected.

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On Wed, Oct 16, 2024 at 10:27 AM, G0TXL wrote:

Thanks; I agree it's expected the bands may have different efficiency. In my case 10m was quite a bit lower output and higher draw, and I saw that running 10m also heated the finals much faster than other bands. I would like to troubleshoot this more, but other than messing with the winding spacing I'm not sure where to start. Now that I run it with a little fan cooling the finals most of the time I don't worry about heat as much. But interested to hear suggestions or other builders' experiences. (Should note my QDX also has TN0110 finals instead of BS170 now, but I also saw differences in heating across the bands with the original BS170s.)