QMX+: Hearing a tone only when LSB is selected
Hello everyone,
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Ive been trying to clean up the transmit audio on my QMX and QMX+. I can¡¯t seem to get rid of the distortion on either one. I have been able to get rid of background noises by reducing gains on different parameters. I¡¯ve tried pretty much every suggestion I¡¯ve read on the groups but it¡¯s still distorted. It is usable but a bit distorted. I¡¯ve tried different microphones. I¡¯m currently running the QRP Guys microphone. I tried a rewired Baofeng spkr mic and while the mic works the audio quality on the QRP Guys mic is much better. Another benefit is it doesn¡¯t drag the radio around like the coiled mic cable does.
This appears on both the QMX and the Plus version.?
I¡¯ve noticed on the Plus that whenever I¡¯m in LSB mode above 17 meters I get a constant low level whistle or tone. If I switch to any other mode it goes away. It almost sounds like an AM carrier. It varies a bit in time and amplitude. It doesn¡¯t do this on the QMX. Could it be the GPS on the QMX+ Causing it? I¡¯ve disconnected the antenna but that doesn¡¯t stop it.
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Is anyone else seeing this?
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On another note, what¡¯s the possibility that Hans could have a troubleshooting seminar for the QMX line of radios at the Hamfest next month? Perhaps a course or workshop targeting the most common issues and how to resolve them. Like tx audio distortion and calibration issues. I¡¯m still on the fence about going to the event. I could probably find a reason to fly across the country if a class were to happen.
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Don.
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QMX Blown Finals. Will a DC-DC Adjustable Buck Converter prevent future failures?
I suspect that my factory built QMX has a blown BS170.
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I was running FT8 on 15m into a resonant antenna tuned with an external SWR analyzer. The rig measured the SWR at 1.26:1. I don't believe that the SWR changed at all during the operation. I checked it again when I noticed the power drop, both on the rig and with the external meter. It was still about 1.26:1. I think I can rule out high SWR.
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Here is a list of output powers that I measured when new with the battery, as recorded at the factory, and after the failure:
20m has 3.7 watts on Talentcell battery (Factory 3.8 watts) (After the failure 2.2 watts)
17m has 4.5 watts on Talentcell battery (Factory 4.5 watts) (After the failure 2.2 watts)
15m has 4.7 watts on Talentcell battery (Factory 4.6 watts) (After the failure 1.9 watts)
12m has 3.5 watts on Talentcell battery (Factory 3.4 watts) (After the failure 1.9 watts)
10m has 3.8 watts on Talentcell battery (Factory 3.6 watts) (After the failure 2.0 watts)
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I use a dummy load and a mini QRP Power Meter like this one to measure power:
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I use a Talentcell YB1203000 (12v, 3Ah) battery which my DVM is measuring 12.3v fully charged. Could it be that the extra 0.3v is too much for the BS170's especially on higher frequencies? If so, would a "DROK DC-DC Adjustable Buck Voltage Converter Stabilizer 6-32V to 1.25-32V LCD Display Constant Volt Amp 6V 12V 24V Step Down Voltage Regulator Power Module" prevent future failures if I reduce the voltage to 11v?
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I've read about the addition of a couple of zener diodes (1N4756A) to the BS170s of QDXs. Would this also provide protection on the QMX?
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I haven't inspected the rig yet but will follow these instructions found here to repair it:
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I know that FT8 is 100% duty cycle and that can be hard on rigs but I'm wondering if I should just use my QMX for CW. I'd rather be operating than changing blown FETs.
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Thanks.
Paul VA3ZC
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
I managed to get the QMX+ working with the FreeDATA software yesterday using the 1_01_003 firmware in SSB mode. ?Setup is a Raspberry Pi 5 running the latest Debian 12 using a USB connection to the QMX+ for CAT and audio.
I am in Maine, and managed to exchange several messages with a station in Ohio last night with 2.6 watts on 20m.
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Great little radio!
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-Dj
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Re: Here's hoping for QMX+ v2
QSX? - That file is already closed: /g/QRPLabs/message/140815
Tnx, missed that one ... Good discussion on the complexity and point of adding a 10W linear considering you essentially already have one with CESSB (for SSB at least). To me, main success factor of the Q range is that they are small,? lightweight and only require small batteries. So that shouldn't change whatever lies in the future design path.
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Re: Here's hoping for QMX+ v2
Seems it would be good to have a QMX that has several options for a final amp.
BS170's are cheap but can fail, would be good to have a more expensive option that is bulletproof at 5W,
and some might want an option for higher power.
All should be EER with an appropriate modulator and driven from CLK2 for power efficiency.
If more power is an option then that would need bigger LPF's,
so need pretty much all of the final page of schematics on that other board.
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Here's one possibility:
A cheap all in one board like the QMX we have now, but plug in filters for band switching to keep the price rock bottom.
A connector on that board that can go to an optional second board in the same enclosure,
that second board can have some other final amp with appropriate band-switched LPF's.
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An optional RPi-Zero (or similar) with a color touch screen mounted on the top surface of the enclosure
for those that want such a thing.??
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And of course, I think the SMPS's should use standard IC's as per this thread: ?
Far more robust, no additional cost, no CPU overhead, working great for me.
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Jerry, KE7ER
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On Wed, Apr 16, 2025 at 06:28 AM, RS wrote:
Adding a robust 10W MOSFET PA would be welcomed by many, but of course this is a major design change with a heap of consequences? e.g. cooling, larger toroids, higher cost, etc. etc. and we would be leaving the pure QRP segment.
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Re: QMX+ with WA3TFS amplifier
Hi Jim:
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I have C16 on a front panel switch to choose slow or fast. I thought about using the PTT function from the QMX as well but using it as a switch to ground going to the diode at the relay. But it wouldn¡¯t do anything about the switching time. Your idea sounds intriguing.?
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Keep me posted on this - if it works, I¡¯ll do the same thing !
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73, Jamie
WB4YDL
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Ron... You are correct. Still have a couple IC's with questionable readings. On the way to get my torn bicep repaired so will continue later. Your help is much appreciated... Ron
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Re: QMX+ with WA3TFS amplifier
Stan, thank you for the comment.? I will look over the PTT FET switching circuits in the QMX and Hans' 50W amplifier pin switches.
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73,
Jim - AE5JE
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Thank you Hans.? Time to do so on my high band QMX.? Fingers crossed ?
On Wed, Apr 16, 2025, 12:49?PM Hans Summers via <hans.summers= [email protected]> wrote: Hello John
I think there are still some adjustments I need to make here. But anyway everyone can easily install it, firmware updates are extremely easy to do. Everyone can (and should) do it.?
73 Hans G0UPL
Hello Hans.
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Likely a premature question with the QMX/+ still in beta firmware release.? Are there plans anytime soon to ship assembled QMX/+ units with SSB firmware preinstalled?? Thanks.? John KC1VPP
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Hello John
I think there are still some adjustments I need to make here. But anyway everyone can easily install it, firmware updates are extremely easy to do. Everyone can (and should) do it.?
73 Hans G0UPL
Hello Hans.
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Likely a premature question with the QMX/+ still in beta firmware release.? Are there plans anytime soon to ship assembled QMX/+ units with SSB firmware preinstalled?? Thanks.? John KC1VPP
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Hello Hans.
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Likely a premature question with the QMX/+ still in beta firmware release.? Are there plans anytime soon to ship assembled QMX/+ units with SSB firmware preinstalled?? Thanks.? John KC1VPP
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Hi Randy
Yes, a way of loading and saving settings is still on my ToDo list.?
73 Hans G0UPL
I seem to recall a while back, discussion regarding the ability to export and import configuration files.
With 4 QMXs, 6 QDXs and all of the associated configuration settings, it would be quite nice to be able to keep a text copy of my "standard" configuration settings.
Even if it is as basic as doing a "show config" that can be screen scraped and copied from Putty, modified, and then pasted back in with a "config x" command.
Is this on your roadmap?
PS. no pressure and not asking for an estimated delivery date. :-)
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Randy, N4OPI
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Re: QMX/QMX+ internal Transmit Voltage measurement question
I do all of my software development either on Linux or MacOS and usually both at the same time. Years ago, Apple eliminated gcc and g++ from their tool chain and switched to clang. Clang is available on all *nix platforms but I¡¯m not sure if it¡¯s compatible with cross-compiling to STM binaries. The nicest thing about clang is its more human-readable warnings and errors. I don¡¯t know if it offers profiling though and can¡¯t state anything about its execution efficiency w.r.t. gcc/g++. Still, since clang is Apple¡¯s default compiler, I decided to use it under Linux as well to keep my make files consistent across both platforms.
I also use valgrind on Linux to check for memory leaks. Hans, you¡¯ve said you don¡¯t use dynamic memory allocation so that¡¯s not an issue. Of course, you still need to worry about stack overflow.
Floating point division is a CPU hog, considerably more than floating point multiplication. It¡¯s a necessary evil for statistics calculations such as averages, variance, and standard deviation. Like Hans, I¡¯ll take every opportunity to avoid division and implement it as multiplication if possible.
One nice feature in FPGA development is the ability to trade off DSP block utilization for execution speed. I can add more DSP blocks for faster execution time or allow slower execution speed to save DSP blocks.?
It can be tricky determining the best course of action in CPU environments where you don¡¯t have control over the hardware. But it certainly inspires innovation and deep learning of what works and what doesn¡¯t.
Tony AC9QY On Wed, Apr 16, 2025 at 6:52?AM Chris, G5CTH via <chris.rowland= [email protected]> wrote:
I'm not in the least surprised that SSB maxed out the processor.? Corollary of Parkinson's law maybe.? Processing requirements expand to match what is available.
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Do you use fixed point arithmetic?? This uses integer arithmetic but choosing a position for the binary point.? And choosing the values and ranges to make divisions in particular binary.? For example in this example if the factor was 6.4 instead of 5.7 the conversion in decivolts would be a 6 bit shift.?? It would take some careful resistor selection but with 1% resistors something could be done.
This is of course overkill for this measurement, which isn't done often, but the inner loops of the SSB code might benefit from using fixed point, and maybe even hand optimising for the really critical parts.? I've done that, using a profiler, or even setting and clearing an output pin and using a scope to see where most of the activity was, then had optimising.? Things such as avoiding register shifts and storage of temporary variables could save 20 to 30%.
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All really difficult but a lot of fun.
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Re: QCX Mini Displaying //???/??/
Hi Matt. The issue still really sounds like a loose connection somewhere. Maybe since you are sure your soldering is OK you could try giving a gentle twist to the tabs on the back side of the LCD module to tighten them up. The one that you had to bend per the instructions may need a tightening twist to it as well. Connections inside between the LCD unit and the backplane circuit are just contacts that need to stay reasonably tight. In the unlikely event that it's something glitching in the firmware, then a factory reset might fix it. If you don't have meaningful intelligence on the screen long enough to get through that process you could always do it by counting button pushes and rotary encoder clicks. I actually wrote down the "blind" procedure to do a reset. If you need that, let me know. Good luck ..73 ... Ron
New QCX Mini (20m) build and everything seems to be working except for the screen will go blank and/or display a mix of /'s and ?'s after the initial boot screen. Boot screen always displays both lines of text and then roughly half the time I get the random mix of ?//? on just the top line or a single black character on the top right. The other half of the time the screen displays the frequency on the top line and I'll get a few button presses before it again falls back to the ?/???? junk. Pushing any of the buttons updates the line but never goes back to anything other than a single black box or the junk characters.
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I've inspected the board pretty closely, re soldered pretty much everything on the board at this point, and checked continuity between the screen and IC2 pins which all seems to check out. I've also checked the voltage on all the screen pins with a multimeter and while they aren't exactly what is in the build guide they seem to be within the expected operating range. That about hits the limit of what I know to do for troubleshooting, any advice would be more than welcome.
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This is curious behavior - I believe there must be something defective in your QMX+.?
The memories in mine function perfectly, sending exactly what is in the memory every time.
With one exception: there is a firmware issue that can leave 'unseen' characters in the memory that get sent (I documented this in a separate thread) - but even in that case, it sends the exact same thing every time.
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Does yours always send correctly with an external key? (I'm wondering if this is a flaky TX issue rather than a flaky memory issue).
And it also is flaky with your logging program via CAT?
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If it is just flaky sending from the keyer memory, I would think maybe your processor/eeprom interface has a problem.
But CAT I think is purely in the processor, if your logger is using the KY commands to send - so it would be something different.
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Good luck - Stan KC7XE
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Re: QMX/QMX+ internal Transmit Voltage measurement question
Do you use fixed point arithmetic??
The QMX SDR is coded on both receive and transmit using floating point. A big advantage is that you know you've got 24 bits of precision in 32-bit floating point IEEE-754 format. With fixed point (or equivalently integer) you need to constantly worry about scaling your numbers so that the dynamic range window fits the numeric capacity. 24 bits of precision equates to 144 dB dynamic range and is of course way more than the radio hardware itself is capable of. So it's one less thing to worry about. The STM32F4-series have floating point and DSP hardware so it's handled very efficiently (if not infinitely so).?
73 Hans G0UPL
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Re: QMX+ with WA3TFS amplifier
On Wed, Apr 16, 2025 at 07:57 AM, AE5JE - Jim wrote:
plan is to use the QMX +5V PTT signal.? Inputting +5V to the base of the amplifier's T1
Jim, the QMX ptt signal will only source a few mA, so it may not work directly.? It is better to use it to drive the gate of a FET switch.
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Re: QMX+ with WA3TFS amplifier
Jamie, do you have C16 installed in the WA3TFS amplifier?? I plan to build my amplifier without C16 and test with the QMX.? Depending on those results, my backup plan is to use the QMX +5V PTT signal.? Inputting +5V to the base of the amplifier's T1 via the voltage divider.? That should turn T1 on and switch the relay.? This would replace using the rectified RF input to switch the relay and should make the PTT to TX delay effective.? Not an electronics expert, so we'll see if this works.? :-)
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73,
Jim - AE5JE
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I wasn't able to find a suitable BPF combination that worked well for my QDX on 40-15m, and I've instead bypassed it for now with a 1200pf capacitor. This way, the LPF selected is always in line on receive, and I have tried running an external HPF (K9DP BCI filter) that cuts off everything below 3.5 mhz; creating a kind of wideband BPF.? I've played with values in Elsie to make a HPF on the same K9DP board with a 7mhz cutoff, but haven't implemented that yet. That's worked well enough in my US operating. (I know EU areas can have stronger SW BC signals near ham bands)?
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-Nate
N8BTR
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Ron... Tnx for the Heads up! You are correct. I'm scheduled for surgery this afternoon so I will be out of my shack for a while. I did re-check the IC's again and a couple ?are still questuinable. Thanks for your help... Ron ?
On Apr 16 2025, at 8:00 AM, Ronald Taylor via groups.io <wa7gil@...> wrote: Ron, it looks like you might be counting the IC pins wrong. You show about 12 v on pin 5 and about 2.5v on pin 8. It should be the opposite. Looking down on the top of the IC with the notch or dot at the top, the top left pin is 1 and it counts counter clockwise around from there with pin 5 at the bottom right and pin 8 at the top right. Hope that makes sense.?
Ron The QCX was returned to me as "Not Working." I set it up on a 12vDC battery and dummy load. Then used a signal generator and found that the QCX was receiving a signal. Also, using another radio (FT-891) I transmitted and the 891 received the QCX signal. Next I put in on the osciliscope and found that the output was 1V peak to peak. At this point I checked Q1, Q2 and Q3. All were functioning properly. Here I began checking the IC's. The pins I did not list here are within specs. The ones listed were not. IC5 pin 5 (2.28 is actually showing 12v IC5 pin 8 11.67) is 2.55 IC6 pin 3 (1.63) is 2.66 IC6 pin 5 (1.55) is 11.67 IC6 pin 8 (11.67) is 2.66 IC7 pin 3 1.99) is 2.60 IC7 pin 5 (1.89) is 11.67 IC7 pin 8 (11.67) is 2.66 IC8 pin 3 (0.65) is 2.57 IC8 pin 5 (0.65) is 2.57 IC8 pin 8 (11.67) is 2.60 IC9 pin 3 (0.65) is 4.49 IC9 pin 5 (0.67) is 11.67 IC9 pin 8 (11.67) is 2.56 IC10 pin 5 (4.21) is 11.67 IC10 pin 6 (3.94) is 5.94 IC10 pin 8 (11.67) is 5.90 This is as far as I got. Sorry for the 1st email, Hans. I have torn the bicep in my left arm and probably took too many pain killer before I emailed.. Hi Hi Any help will be most appreciated... Thank You Ron Pearson KA5HZV
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Dj Merrill
AE5JE - Jim
Ronald Taylor