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Strange/Poor Power Performance QMX+
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Hello,
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I recently bought a QMX+ and had a lot of fun building it and using it so far, but, my biggest problem is the inconsistency of power over the bands. I've tried quite a bit of stuff suggested (re soldering, touching up the joints, verifying continuity, etc.) but I am now out of ideas on what to do. I've attached photos of my RF filter sweeps, SWR sweeps, LPF sweeps, and I/Q sweeps. I am out of ideas on what to do and just want to make sure I am getting the most out the device.
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Also I am sorry if I am heading in the wrong direction with this, I am new to the hobby.
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Current RF power:
6m -> 0.9W, 1.43SWR
10m -> 1.8W, 1.22SWR
12m -> 3.0W, 1.18SWR
15m -> 3.3W, 1.12SWR
17m -> 2.3W, 1.15SWR
20m -> 3.1W, 1.10SWR
30m -> 4.4W, 1.07SWR
40m -> 4.1W, 1.04SWR
60m -> 4.4W, 1.05SWR
80m -> 5.4W, 1.05SWR
160m -> 6.0W, 1.04SWR
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¿ªÔÆÌåÓýHi there. You should start with examining SWR bridge then trifilar transformer.. These are two CRUCIAL parts to get it working right. ? Of course I assume You did all the sweeps on dummy, but looking at your SWR sweeps, apparently something is not OK. You did not attached close pic of PCB so hard to tell but please compare your SWR and RF sweeps with my QMX ( They're similar in general, your 80m RF sweep looking exactly as mine LOL and nothing we can do with it ) ? BTW, I was 200% sure I did not made any mistake, pffff, I am working with RF daily and such things are POC, but we are human. Errare humanum est ;-) ? If anything drop me a line. ? 73 Greg SP3RNZ ? ? From: [email protected] [mailto:[email protected]] On Behalf Of groups.3dxvx via groups.io ? Hello, ? I recently bought a QMX+ and had a lot of fun building it and using it so far, but, my biggest problem is the inconsistency of power over the bands. I've tried quite a bit of stuff suggested (re soldering, touching up the joints, verifying continuity, etc.) but I am now out of ideas on what to do. I've attached photos of my RF filter sweeps, SWR sweeps, LPF sweeps, and I/Q sweeps. I am out of ideas on what to do and just want to make sure I am getting the most out the device. ? Also I am sorry if I am heading in the wrong direction with this, I am new to the hobby. ? Current RF power: 6m -> 0.9W, 1.43SWR 10m -> 1.8W, 1.22SWR 12m -> 3.0W, 1.18SWR 15m -> 3.3W, 1.12SWR 17m -> 2.3W, 1.15SWR 20m -> 3.1W, 1.10SWR 30m -> 4.4W, 1.07SWR 40m -> 4.1W, 1.04SWR 60m -> 4.4W, 1.05SWR 80m -> 5.4W, 1.05SWR 160m -> 6.0W, 1.04SWR ? ? |
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Hello :)
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First, thank you so much for responding and telling me to look at the SWR bridge and trifilar transformer, that GREATLY improved the performance on all bands (re wound SWR bridge and re soldered trifilar). It still suffers quite a bit on the lower bands and power for some reason isn't consistent over the whole band? I've attached photos of the PCB but there isn't anything notable that I can see. I assume to further improve performance I should take a look at the filters now? I might also rewind the trifilar since it helped a lot with the SWR bridge.
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New power:
6m -> 1.1W
10m -> 3.4W
12m -> 2.7W
15m -> 3.7W
17m -> 2.6W
20m -> 3.7W
30m -> 5W
40m -> 4.6W
60m -> 5W
80m -> 6W
160m -> 6.6W
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Hello,
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what are you looking to improve here, exactly? The values of output power you listed seem to be consistent with the expected ones for a typical QMX+ build...?
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You can perhaps squeeze a bit more power on 6m by playing with the corresponding LPF (if you live in the Northern emisphere you will have time until next May to do that HI), but the rest looks totally in line with the power levels reported by other builders.
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72/73 de Enzo M0KTZ |
¿ªÔÆÌåÓýOKay. My personal point of view below. ? You see quite an improvement with just checking few vital places in QMX. If I were You, I will dig deeper (and I will in mine QMX for sure) I wasn't sure about my QMX, and already asked Hans and Ludwig (THANK YOU guys! ) if my QMX is "working" OKay. Apparently it is, within expected results (but that's not enough for me). My first HB radio made in dark ages, behind steel curtain in Poland, without nowadays cores, DMM's and other stuff. Tweaking, testing, changing - it's long story. Doesn't matter kit or build from scratch all need lot's of work.? ? So, as You probably read in manual, 75% success of power output is T507. This need to be really perfectly done, bear in mind You want to get it work on 50MHz. It's not 80 or 40m. No lousy connections, special care for enameled wire needed, etc. So, I will rewind it and make it RWTST (what type You have?) - as per manual it give better results especially on higher bands - and if so, 6m should be improved as well. Here You are with great example how to do it https://www.youtube.com/live/Wz_cCifwAJE Run the diag before replacing and after. ? Next step. Tweak your LPF for 6m. It's easiest part - only two cores involved. ? Next I will get another FT37-43 and make second trifilar transformer ;-) and check and check if I/Q response will change ( it will for sure, question which way) I found it very important for overall performance, even little too long legs make a difference (tested)??? ? Last, remember that SWR bridge in this radio is very simple, but still it have to read frequencies ~50MHz. Unnecessary long legs, non symmetrical windings, crossed wires - will NOT do it properly at 28/50MHz. I know one can say it will have minor impact.? But few "minor impacts" can lead to frustration and failure. It's not acceptable for perfectionist, is it ? :-))))) ? P.S. Next time You add sweeps please label them like RF 80 or something. ? Good luck. ? Greg SP3RNZ ? ? ? ? From: [email protected] [mailto:[email protected]] On Behalf Of groups.3dxvx via groups.io ? Got a little too eager, forgot to attach the images, whoops! Also forgot to mention, but my filters do roughly look like the photos provided. |