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Re: QMX new build showed up as USB but unresponsive after firmware transfer
On Sun, Feb 23, 2025 at 09:41 PM, Florin wrote:
If I'm not mistaken the only SMPS available for purchase separately were for REV 1 boards,Florin, no, the available spare SMPS boards are good for all QMX revisions. And these boards are with some changed elements compared to REV 1 to enhance the robustness. ?
And congratulations to your new build!!!
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73 Ludwig |
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Re: QCX 50W PA multibanding?
#50wpa
I like this idea, Don. I built the PA for 7 MHz (for emcomm this would be the highest band).? For the other two bands, 60 meters and 80 meters, I could perhaps live fine with just one simple elliptical lowpass aimed at suppressing 7 MHz.? 10 and 14 MHz are out of the game in this case.
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Two ideas:
- in LTspice I was unable to design a lowpass that would work fine for both 80 and 60 meters (in OK we have the WARC 15-15 segment, i.e. 5351.5 to 5366.5 15W PEP) - 7 MHz is too close to 5.3 so 2nd harmonic suppression was not great, despite the assumption that push-pull amp creates relatively weak 2nd harmonic. 3rd harmonic of both 3.6 (central spot of all digital mods on 80m) and 2nd harmonic of 5.3 should be well suppressed by the original lowpass. So I need to resolve just the 2nd harmonic from 80 meters (7.2) and whatever else above that is attenuated is a bonus.
- I cannot just take some 5.3 MHz lowpass and put it as-is after the original 7 MHz lowpass because the input shunt capacitor of the appended LPF would add to the output capacitor of the original LPF and that would result in a mess. So the "appendix" LPF must be designed as "continuation" of the original built-in LPF. But that should be easy with LTSpice.
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I will try to simulate this, build it, and if it works I will post it here.
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73 Jindra
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On Fri, Jan 5, 2024 at 01:25 PM, Donald S Brant Jr wrote:
To keep it simple in an emergency situation you could just use outboard lowpass filters, swapping them manually as needed.? ?Put your highest-band filter in the box (always inline) and add lower-band ones when required.?? |
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QCX buzzing sound on key down
I have a loud buzzing on key down at times. It is not transmitting then. If I power off and on it usually goes away and sounds ok on my receiver. The finals have been replaced and power is about 4.5 watts. SWR is about 1.4 and battery is 12v. It’s random. It’s easier to fix if something stays broken. Microcontroller issue? I might have a spare but this was built several years ago. The fact that it just makes a loud buzzing sidetone with no iambic keying even though it’s selected puzzles me. After rebooting it usually works. Another transistor in the keying circuit questionable? Waveforms looked ok. May need to look again.
73s John N4HNO |
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Re: QCX 50W PA multibanding?
#50wpa
You are right, Don. I think I wrote this before having read Hans' description of the method to obtain negative bias for 1N4007 in the manual. I guess I was exhausted by the building process and at the same time excited by how well it worked, so I stopped reading early :)
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Jindra
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On Fri, Jan 5, 2024 at 01:25 PM, Donald S Brant Jr wrote:
To keep it simple in an emergency situation you could just use outboard lowpass filters, swapping them manually as needed.? ?Put your highest-band filter in the box (always inline) and add lower-band ones when required.?? |
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Re: QMX new build showed up as USB but unresponsive after firmware transfer
Some learnings and a success (eventually, with another build)
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Finally had time to wrap up this topic, so I will provide an update for anyone facing the same issues as I did. Hopefully this helps some poor soul going through what I did.
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My initial build had 2 solder joints that needed touching up: an SMPS GND pin on the main board, and one pin on the LCD potentiometer. Unfortunately while trying to debug the GND connection on the SMPS while powered on, I believe I may have shorted some connection with one of the DMM probes, which caused damage to ?one of the diodes on the board. This resulted in the radio not powering up at all after that. Symptoms included popping in the headphones while the power button was pressed, rig powering on only for the duration while the button was kept down and then powering off immediately on releasing it.
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I decided to replace the SMPS boards. If I'm not mistaken the only SMPS available for purchase separately were for REV 1 boards, so because of that plus an abundance of caution I ordered a new QMX kit, with the idea to do a better job on a second try.
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Today I started building the second kit and a few hours later I got to the step where you plug it in and hope for the best. It connected to the computer, I loaded the firmware and it rebooted to a fully working rig! I've yet to test it for power output because my antenna only has an SO-239 connector and I haven't got any BNC lying around, but I'm glad the learnings from the first build transferred over to a successful one. And now I have spare parts too in case I need that.
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My takeaways from this whole experience are:
- solder joints can look perfect yet still not make contact
- wielding the DMM probes while the radio is powered up is a bad idea most likely
- this is not an easy kit to build (today I had an accidental soldering iron slip which put solder across 3 pins of a close proximity IC. Almost had a heart attack but after 15 minutes of struggling with the iron and a sewing needle, I managed to break the short without damaging anything else)
- despite it being challenging, after the first try you really can go full speed on building this kit. I recommend you keep going even if at first it might have been a failure
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Many thanks to all those who shared their advice and thoughts in this thread, and despite me not having proper equipment for many of the testing procedures suggested, they've all helped me sort out what to look for in my second build, even before applying power. |
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Cal (and Stan)
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I don't mean to hijack your thread but as one of the initial group buy participants, I just want to publicly say thank you both for ALL the efforts that you both put into organizing this and keeping it low cost and affordable.? I am sure that you both would have preferred to spend this time on the air or with family.? Thank you both.
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Len KJ9E |
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On Tue, Feb 18, 2025 at 02:39 PM, Stan Dye wrote:
From our experience last time, international postage between US and UK or Europe may make the cost quite high (Cal delivered one kit to Germany).? We will contact you when we make plans for the group buy. For shipping a single ABS Version 1.2 PCB/PCBA/MPUs kit without BOM parts to Germany, it was critical too keep the mass down, which made it necessary to find a perfectly sized and light weight box (which I just happened to have in my box stash). The total mass was 221g and the cost for First Class US Mail postage to Germany was about $20 USD. Unfortunately, the mass is close to a "price point." At 227g, the price goes up to 28.55 USD! I also sent a few PCBs in a padded envelope to Dirk in Germany, which cost the same. The First Class US Mail prices for a non-flexible envelope and a box are the same.
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The USPS Small Flat Rate Priority box can be used too, which includes tracking and insurance, but it is not as economical for such a light item, which is far cheaper to send via First Class Mail. The Small Flat Rate Priority box costs 47.95 USD to Germany/ That's about the same price as FedEx and UPS!? However, it is worth it for two or more PCB/PCBA units. Up to two Revision 1.2 board sets will fit in a Small Priority box or perhaps a single board set with the BOM parts included. If we ever have a Rev. 2 group buy, I might be able to fit three PCB/PCBA kits into a small box.
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Shipping prices will undoubtedly continue to rise. UPS announced it is slashing its business with Amazon by 50%, and the UPS CEO said it was necessary to mitigate "diminishing returns" or something like that.
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73,
Cal (AD8Q)
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Re: QMX+ with ~1000 tone on 12M & 6M
QMX+ rev.3 9v build.
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I would also like to report the same anomaly observed on 17m and 6m.
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I was 'playing' around with the CW filter and decided to try out the 'none' option, disabling the filter. I started tuning around and all seems ok, I could listen to SSB etc..
I hopped on to the 6m and was met with a very high level of noise. I can confirm that the noise I heard was as described by all on this thread. I can also confirm the CW like clicking noise, short and long random clicks. The noise was all accros the 6m band with filter switched off. The level and noise content did not change.?
I then started hopping around bands to see if I can hear it on other bands. I also found it on 17m.
I shorted out the antenna to isolate any external interference, the noise level and characteristics didn't change.
I went back into the menu and renabled the filter. With the filter now engaged, the noise almost completely disappears, but still could hear the CW like clicking and the 1k tone very faintly.
The noise is generated internally, I'm quite certain of it.?
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Mel. M0KMD |
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Re: QDX - I/Q mode and SSB firmware
On 23/02/2025 14:07, OM5EAX via groups.io wrote:
s there any ready made software, that is recommended to (try to) listen to SSB transmissions using built in sound card?I use HDSDR. I think SDR Console still has soundcard input. I'm not sure what else retains this older soundcard SDR feature. You get a maximum of 48KHz span. Any mode with a requirement of less than 48KHz bandwidth may be used. 73 Alan G4ZFQ |
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Re: QDX - I/Q mode and SSB firmware
Hello,
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Reacting to:
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I'm interested in purchasing QMX+ kit. Is there any ready made software, that is recommended to (try to) listen to SSB transmissions using built in sound card?
So I'm getting clean base band with around 24kHz bandwidth using the soundcard right? Or is there any problem that I would encounter while trying to demodulate voice SSB transmissions there?
73 de?OM5EAX |
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Another Jeff Moore W1NC Repair Rescue
Thank you very much, Jeff for? bringing my QMX+ up to specs after I sent it to you for help with no RX signals. even though audio was functioning.
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I just want to add my voice to the many others in praise of your dedication, expertise and? generosity.? We are exceptionally fortunate to have you available to bring the QRP Labs radios to full potential, no matter their condition when they land on your work station.
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Best 73,
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Bill Jobes? W3WJ
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Richard Dyer
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