#qmx high band harmonics
#qmx
High-band QMX rev2 (2024), 9V version, Firmware 017.? Having fun learning about this radio. LPF cutoffs are good, though LPFs 1 and 2 show stopbands a little high, about –30dB.? I get 4W out on 20m and 17m, less than 3W on 15m, 12m, and 10m.??
I thought I'd take a look at the output spectra, after reading several posts here about harmonics.? I don't have a tinySA, but I do have a 200MHz oscilloscope with good FFT capabilities.? I made the following setup:? QMX --> Dummy load --> 10X probe --> Scope.? The second harmonics on 15m, 12m, and 10m are higher than what I would expect, between 39dB and 42dB below the fundamental.? 20m and 17m are OK, 63dB and 52dB down, respectively.
My understanding is that the push-pull Class D amplifier is effective at suppressing even harmonics, prior to any filtering, so I'd like some ideas about where the high levels might be coming from and what I might be able to do to reduce them.
Thanks!
Eric
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Correct! In my case I smoked out two of the BS170 and ended up with one heathy BS170. QDX is ?still alive and kicking with that one!:)
3x BS170 is absolutely a better option to distribute output power.
So to summarize here is my QDX QRPp setup:
- removed IC2 - 78M05 from pcb.?
- USB socket 5V pin goes to IC2 - 78M05 5V output pin
- In my case one BS170 is active but 3xBS170 is better.
- No 12V connection.
- The whole rig is powered by PC USB. RF power output around 500 mw to 700 mw band dependent.
The advantage of this setup is I carry only my laptop, ebd fed half wave antenna and ?QDX to Park. No PSU. PC supplies at least two hours of continus fun. My laptop is a microsoft surface laptop.
--
?
73, Barb
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Re: Magical smoke out of QDX, two leftmost BS170 very hot
Ah, yes. more data. This happened on 40m, 7074 KHz. I was transmitting sucessfully right before, couple of POTA QSOs, tuned antenna to SWR 1,2:1 (with NanoVNA)?
73 de EA7KLK Volker
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Magical smoke out of QDX, two leftmost BS170 very hot
Hello,?
'fraid my QDX let out the magic smoke today.?
I had one of these rare moments when it would not transmit after changing band / frequency. I unplugged from both PC and power, plugged pwer back in and it started smoking and stinking immediately. Two leftmost BS17o get very hot and smoke.?
12V build, latest Firmware 1_10, being run at 11,3V - first thing I checked was if my downconvertar had gone nuts - no, it hasn't, it's outputting wonderful 11,3V, under load and without.?
Should changing the 4 BS170 (I have been so cautionary to stock some) fix the issue or should I look at something else before, lest I burn them again straight away??
73 de EA7KLK, Volker
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Low Band Rev1 QMX for sale
Hello, I am offering my fully built low band Rev1 QMX for sale. I am a J-STD soldering instructor and experienced kit builder. My QMX worked fine first time with no issues. I am very happy with the rig but enjoyed building it so much I wanted to build another. I am asking $115 for the radio and enclosure + shipping. Please contact me via my email listed on QRZ under my call N9DXP.
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Just to make sure I understand the theory...? 3x BS-170's @ 5v would still result in the same QRPp power out as Barb's 1x BS-170 @ 5v?
Thanks
Jon n0wl
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Re: Brainstorm question: How to "view" QDX LED status remotely?
Hi Donald.? Quite true about the voltage acquisition timing issues.? One solution is to get the voltage before the limiting resistor for the LED.? Then just buffer (if necessary) and low pass the pulsating voltage.
Glory to God in the highest, and on earth peace, good will toward men. Luke 2:14
On Wednesday, February 28, 2024 at 10:26:31 AM EST, Donald S Brant Jr <dsbrantjr@...> wrote:
Watch the update rate on the meter, as well as the ability to disable the auto range.? With a flashing/pulsing LED the auto ranging might get stuck trying to chase the varying signal.
I have seen this happen, the meter just ranges up and down forever and never settles to a reading.
73, Don N2VGU
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Re: QMX on Inovato Quadra
Awesome, glad to hear this.
How are you finding wsjtx on the Quadra? I got it working before (though with a different radio) but to me it seemed it was barely able to keep up with the decodes and many times was too late causing a reply tx to get skipped till the next frame. I eventually dropped it in favor of the pi 0-2 which has a bump up in horsepower over the Quadra and never misses. But it's been a while and maybe I just need to repave it.
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Re: Faulty Progrock2 - no response to ticket
#progrock2
Thanks, but now the PC no longer opens the Progrock programming page, probably because the pic has broken down and is therefore no longer usable.
73 iw2gg Enrico
I have used numerous ProgRock2's without any problems -- I install them in old receivers and transmitters to replace faulty/drifted crystal-based heterodyne oscillators.? What are you trying to do and what went wrong?? Possibly I can help.
73 - Steve, KW4H
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Re: Brainstorm question: How to "view" QDX LED status remotely?
Watch the update rate on the meter, as well as the ability to disable the auto range.? With a flashing/pulsing LED the auto ranging might get stuck trying to chase the varying signal.
I have seen this happen, the meter just ranges up and down forever and never settles to a reading.
73, Don N2VGU
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
Sorry to hear that it’s dead.
No consolation, but it could be worse. I saw an ad a few weeks ago here in UK, for a week old Yaesu FTDX10 that the owner had given 55 Volts… Spares or repairs!
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
Thanks for the help everyone. It was a fun build so when budget loosens up a bit I'll give it another go. Maybe by then the QMS will be out.
73 all
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Re: QMX on Inovato Quadra
She lives! It was plain, old, uncomplicated, simple RFI. Clipped two ferrite beads onto the coax, and another two onto the USB cable, et voila, JS8 and WSJT-X work just fine. Thank you to everyone who contributed help and hints, and I apologize...an Extra really should have known better!
Side note to anyone who wants to use JS8Call, reduce minimum samples to 1 from 480. I don't know if the rise and fall thresholds really make a difference, but 10 minutes of playing around this morning before work led the to reduce those numbers from 80 and 60 to 60 and 40, respectively...it seemed to make the radio "hear" what had previously been a blank waterfall. Made a few contacts after that before my paycheck called to me...
73, see you on the air!
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Would Q204 be as sensitive to ESD? Being connected to an external jack (PTT) isn't it sort of hanging out there like an antenna?
--
Tisha, AA4HA
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Re: Brainstorm question: How to "view" QDX LED status remotely?
Thinking about this some more, a Trinket M0 could monitor the voltage of the LED with a GPIO and output it while emulating a USB keyboard. I use trinkets as keyboards all the time. I have a rotary encoder that outputs the AV keyboard codes for volume up and down on my headless pi as an example. They are cheap. Then you need some PC code to read the keyboard and get you the data. It could be done in a web browser to make a status display you could read via VNC.?
--
Colin - K6JTH?
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Re: Did I fry my QMX SMPS or is it likely worse?
#qmx
Hi Brad.?
I'm by no means an expert in this, but If you're reading single digits of resistance across the 2 rails on the main board to ground with the smps boards removed, then yes, your QMX has likely met its demise. I have a QMX on my bench (in the corner somewhere) that exhibits that condition, and after a quick exchange with Jeff Moore, who has repaired many these units, it became clear that the best way forward was to order a new QMX kit.
The good news is that that strategy has worked quite well for me, and I'm back on the air. ?
How frustrating your situation must be for you! So sorry!?
73
Roy - KI0ER?
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Re: Brainstorm question: How to "view" QDX LED status remotely?
On 28/02/2024 14:10, Alan G4ZFQ via groups.io wrote: an easy way of checking operation is looking for spots on WSPRnet. Or, presuming you are checking by VNC (?) click TX and be monitoring on a local RX.
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Re: Brainstorm question: How to "view" QDX LED status remotely?
Hi Nate.? One quick solution is to purchase a cheap USB enabled DVM with software.? Run the DVM software remotely to monitor the activity of the LED voltage.? Here's one example:
Glory to God in the highest, and on earth peace, good will toward men. Luke 2:14
On Wednesday, February 28, 2024 at 08:41:46 AM EST, natereik@... <natereik@...> wrote:
My QDX is generally "remote" in my attic at my main QTH, running off a laptop up there, 30 feet feet from where I'll sit and "operate." I like the QDX for remote digital work, because there's no audio routing involved, no other software needed to operate, and I don't need huge bandwidth if I remote desktop in.?
BUT, I have run into situations at home where I've accidentally bumped a slider in WJST-X....and eventually figured out I wasn't transmitting even though WJST-X seems to show that I am. I go up to the attic and then can see the LED status indicator and realize there's something wrong with the audio.?
? ? ?I'm looking at putting 2 or 3 QDXs to the same computer at my 2nd QTH eventually, and have realized this could be an occasional issue there, as I'll want to remote operate from home. From what I can tell, there's no way through Putty or any other native way to "see" the status LED (or read the status) via a computer... I have low bandwidth at my cabin, upload speed is slow there (600 kbps), so a camera with video is out of the question. So I'm curious as to how you think one could most easily "remote view" the status LED on a QDX or 2 without an insane amount of complexity??
Phototransistors into Arduino inputs? Somehow monitor the current of the LED, but fast enough to see what it's doing? (as in, need the resolution and speed to "Read" flashes vs the 1hz sine wave, etc) Of course this isn't an everyday need, so if it's just ridiculous to do so, I'll skip it. But was thinking there may be a simpler way than what I'm coming up with.?
Curious as to what others think, as this is not an area of my expertise.?
-Nate
N8BTR
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Re: Brainstorm question: How to "view" QDX LED status remotely?
On 28/02/2024 13:41, natereik@... wrote: But was thinking there may be a simpler way than what I'm coming up with. Nate, I do not know what you would do if a LED was not pulsing? But an easy way of checking operation is looking for spots on WSPRnet. I run WSP{R/FST4W on at least 3 RXTX QDXs and the situation you describe, no TX, is very rare. 73 Alan G4ZFQ
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Re: Brainstorm question: How to "view" QDX LED status remotely?
Could you add a webcam to the remote PC, and point it at the
devices, so you can view them remotely? You could also set up a
Raspberry Pi and camera, and use that for viewing.
--
Paul
MW7PAJ
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My QDX is generally "remote" in my attic at my main QTH,
running off a laptop up there, 30 feet feet from where I'll sit
and "operate." I like the QDX for remote digital work, because
there's no audio routing involved, no other software needed to
operate, and I don't need huge bandwidth if I remote desktop
in.?
BUT, I have run into situations at home where I've
accidentally bumped a slider in WJST-X....and eventually figured
out I wasn't transmitting even though WJST-X seems to show that
I am. I go up to the attic and then can see the LED status
indicator and realize there's something wrong with the audio.?
? ? ?I'm looking at putting 2 or 3 QDXs to the same computer
at my 2nd QTH eventually, and have realized this could be an
occasional issue there, as I'll want to remote operate from
home. From what I can tell, there's no way through Putty or any
other native way to "see" the status LED (or read the status)
via a computer... I have low bandwidth at my cabin, upload speed
is slow there (600 kbps), so a camera with video is out of the
question. So I'm curious as to how you think one could most
easily "remote view" the status LED on a QDX or 2 without an
insane amount of complexity??
Phototransistors into Arduino inputs? Somehow monitor the
current of the LED, but fast enough to see what it's doing? (as
in, need the resolution and speed to "Read" flashes vs the 1hz
sine wave, etc) Of course this isn't an everyday need, so if
it's just ridiculous to do so, I'll skip it. But was thinking
there may be a simpler way than what I'm coming up with.?
Curious as to what others think, as this is not an area of my
expertise.?
-Nate
N8BTR
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Barb WB2CBA
Donald S Brant Jr
Tisha Hayes, AA4HA
Colin Kaminski