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QMX+ points A continuity check to ground question
2
On p25 of the Rev 3 QMX+ manual, there is a check for continuity to ground from three points A. BEFORE installing T501, when checking the three points A, I get about 15 ohms with the DMM black lead on the ground connection, but open circuit (desired) with the leads reversed (ie red lead on the ground connection). Is this to be expected? The 4 BS170's ARE installed. I am troubleshooting a continuity check problem identified after having installed T501 (now removed). Thanks Steve AK0M
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GPS module GY-GPSV3-NEO wont change baud!
HELP! I need to change my QRP Labs GY-GPSV3-NEO module, which has the UBlox NEO-7M-000 chip on it to 4800 baud, the old NMEA 0183 standard for the TinyTraker3 APRS units. I can use the UBlox u-center25.03 and everything I receive and send from it appears to work, telling me that the RS232/TTL interfaces that I try are correct. However, going into Messages View - UBX - CFG - PRT - TragetUART1 (or any other) setting BAUDRATE to 4800 and hitting the Send button makes NO CHANGE (EVER). It stays at 9600 Baud! Is there another way to try this and make the change permanent? Perhaps there is an inhibit connection on the chip? Or some sort of authorization command? Connecting a terminal program gives me the continuous GPS strings so the module is correctly putting out my location etc., so that part is also working fine (at 9600). I appear to be stumped! Miniature GPS units running at 4800 Baud are pretty rare and I want to resurrect my Altoids Box Pocket Tracker with one to make it truly pocket size, again. Thanks for any advice or help. 73 - Mike VE3EQP .....>
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Tariffs?
28
Will USA tariff laws affect the import pricing of Hans’ great radios/kits into the USA?
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Broken L512 toroid.... T37-10 (Black)
5
#toroid
#problem
I've broken one of the T37-10 (Black) L512 toroids. Do you know where I might get a replacement? Thanks, Bill
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QMX and power bank PD
37
Is the QMX itself in any way capable to negotiate the required voltage with the power bank PD? In other words is a 12V trigger cable required or not? I feel more comfy with a trigger cable as it steers away from any negotiating. 73 es dx
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On 4/07/25 I had a CW practice / rag chew session on 20 meters. I worked four stations: Date / Time Call Bnd Frequency Mode Power Rec Snt Name SPC# Comments Off 4/7/2025 14:40 W0GIB 30 10.115 CW 100 579 559 Craig MN K3 at 100 watts 100 ft sloper doublet 15:23 4/7/2025 14:05 K4HPP 30 10.106 CW 5 559 559 Jim TN K3 at 5w watts 100 ft sloper doublet 14:22 4/7/2025 13:21 K7MOA 20 14.045 CW 100 599 559 KEITH TX K3 at 100 watts 100 ft sloper doublet 13:32 4/7/2025 13:00 KI5JG 20 14.045 CW 100 449 339 Jim TX K3 at 100 watts 100 ft sloper doublet 13:17 Conditions were OK. 30 meters seemed to be better than 20 . SSN = 140, SFI = 167, A = 20, K = 2. My next CW practice session will be April 08 at 09:00 EDT / 13:00 UTC on 30 meters. Anyone and everyone is welcome. This practice is intended for operators who are new to CW or they need some practice. IT DOES NOT MATTER HOW POOR YOUR CW IS. Mistakes are OK. Poor fists are OK. Slow speed is OK. Really slow speed is OK. This practice is meant for you to improve your CW. I will do my best to adjust to your skill level. Operate at any power level. If several stations show up, I will operate as a round-table control station. I will do it as a round-table so everyone gets a chance to transmit. Please listen to my directions. Details: Date - April 08 2025 Time - 09:00 EDT 13:00 UTC Band - 30 Meters How to find me - I will find a clear frequency and call CQ. Go to the Reverse Beacon Network and search for my call sign AB8DF. That will tell you what frequency I am on. Tune your station to that frequency and if you hear me give me a call. If there is a QSO in progress, please wait for a break in the action. Then send your callsign. If I hear you, I will invite you to join the QSO and start a round-table QSO. Reply to this email if you have questions. IT DOES NOT MATTER HOW POOR CW IS Ed AB8DF_._,_._,_
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QMX snags epic DX during greyline!
Well the QMX masterpiece has pulled off the greatest miles per watt of my life, using my homebrew EFHW. I am still is awe to put it mildly. I worked FR8UA at greyline from Montana for a distance of 10,583 miles on FT8. Thank you Hans for all your hard work on this radio, it's truly amazing! John
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Does L502 cause excessive voltages on the QMX finals?
22
The four BS170's and T501 are arranged in a standard voltage mode class D push-pull amp. The center tap of T501's primary is normally a DC voltage source, as it is on the 50W QCX amp. When one set of BS170's pull one side of T501's primary to 0 volts, the other side pops up to 2xVdc (so 24v if operating from 12v). And then the other set of BS170's pull the second side low, creating a square wave at the transmit frequency with a pk-to-pk voltage of 2xVdc across T501's primary. Since the LPF on the secondary of T501 allows through only the fundamental to the 50 ohm external load, the harmonics are blocked by the LPF on the far side of T501, and the current through T501 is a sine wave. The current drawn from Vdc at the T501 primary center tap is a rectified sine wave. Seems to me that adding L502 would enforce a constant current into the T501 primary center tap, not a rectified sine wave. And that the extra current with nowhere to go would be piling up, causing excessive drain voltages that might blow the BS170's. The above paragraphs were originally buried in message /g/QRPLabs/message/139736 Attached is an LT-Spice simulation schematic of the QMX final at 3.57mhz, with and without L502. I'll place a copy of that simulation schematic in the files section under KE7ER. It uses 2n7002 FET's since that is what was handy under LT-Spice. With L502, the Vds on each BS170/2n7002 is very abrupt and spiky, roughly double what it is without L502. Without L502 the voltage across the drains is close to the expected square wave, but output power is reduced. Currents from T501 are rather ugly in both cases, but close to a square wave with L502 and close to a sine wave without L502. I find it curious that a square wave current can exist there since the LPF should be blocking it. The simulation shows the fundamental current going through L508/L1, and the harmonics going down through C515. So the LPF behaves differently than a series LC filter would, and perhaps differently than what would work best with a voltage mode class D amp. It seems that T501 is expected to pass some of the odd harmonics on all bands of interest for this to work well. A very tall order at 50mhz for a transformer that must also work at 1.8mhz. Comments? Jerry, KE7ER
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QMX+: Broken L102
3
I finished building my QMX+ today and on inspection I see I've broken the core of L102, one of the switching power supply inductors. It looks like both leads of the winding are still connected to the board. I'm not going to try powering it up until I get a couple of questions answered. 1) It looks like the core snapped off almost flush with the bottom flange, which is still attached to the PC board. The ends of the winding are still connected to the board. Would it still work if I just used cyanoacrylate glue to put the core back together? 2) If the answer to #1 is "no," can anyone suggest a suitable replacement inductors that's available in the U.S.? Digi-Key doesn't seem to carry anything of similar size that's greater than 220 uH. This one is 330 uH. Dave, WD8CIV
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Good evening! Big thank you to Hans and everyone else in this forum! I had a lot of fun building these kits and I couldn’t have successfully completed them without the folks who ask and answer questions here. I wanted to make this post to thank everyone but also to detail some of the problems I encountered, the equipment I used, and also how I resolved them. This is a long post for anyone who’s interested but TLDR: I built 2 QMX+s and 1 QMX and all three needed new PCM1804s. I purchased a QMX+ in May and a couple weeks later got to work. I had built a couple other kits and antennas previously but this was the most involved so far. I was able to make it through the build and load firmware but I couldn’t run all of the self-tests and the audio was loud static. I didn’t have enough experience or equipment to troubleshoot myself but luckily Jeff Moor W1NC reached out and offered to help. See /g/QRPLabs/message/126274 for my original post. I mailed him my QMX+ and he got it back to me in about a week with several fixes. It had several bad joints, insufficiently scraped enamel, a bad PCM1804, and a bad inductor. Thanks Jeff for your knowledge, experience, and willingness to help the community with your excellent service! I’m extremely pleased with the outcome and my QMX+. I used: A Weller 70W digital soldering iron 63/37 Kester .20 solder 30X/60X loupe https://www.amazon.com/gp/product/B078N34WZR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 LED Head Magnifier https://www.amazon.com/gp/product/B07T4KPYN2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Crescent shear cutter/pliers set from Home Depot A couple of different helping hands type devices Solder wick & plunger type desolderer Flux paste I primarily used the conical soldering iron tip with success but in retrospect, I should have primarily used the wedge tip. The head magnifier with 3x magnification, plenty of light, solder wick, flux, and desoldering tool were critical. The loupe was ok but the head magnifier would have been enough. I ruined the side-cutters on solder wick. Pleased but not content apparently because in July, I purchased another QMX+ so that I could use the lessons learned from the first unit and hopefully successfully build another myself. The kit stayed in the box until my wife & kids went on vacation for about a week. Over a couple of evenings, I had a great time building the kit, using all my new knowledge and experience, but when running the terminal tests, I had bad results on Audio Filter Sweep/RF Filter Sweep/Image Sweep/ADC IQ test. I reworked some of my joints but to no avail. Some example scans, before and after 1804 replacement, are attached. With bad PCM1804 I started diving into groups.io posts and determined that maybe I should invest in more test equipment and that I might have a bad PCM1804 chip. I ordered two more PCM1804 chips (just in case I ruined one). I also ordered a QMX because I was more confident in my kit building skills. In the mean time, I also purchased an LCR meter, a TinySA Ultra (for its signal generator), and an oscilloscope. Probably overkill but I had my eye on them for a while. Over the winter holiday break, I built the QMX. I enjoyed and had more confidence in my build but I had very similar problems to my 2nd QMX+ build during self-tests. During this build, I used a grounding strap/bracelet the entire time so I was pretty sure it wasn’t static discharge related. What are the odds I’d have the same problem twice? I found this post /g/QRPLabs/topic/109639794#msg133769, indicating the PCM1804. I did the diagnostic tests from /g/QRPLabs/wiki/37111 and determined that replacing the PCM1804 was my next step. Luckily I had two new PCM1804’s in stock although I previously intended on only needing one. After doing research here and on youtube for replacing SMDs, I got a ChipQuik kit and a hot air rework station. After doing some tests, I decided I would just use the ChipQuik, which is basically easy-mode for low-skill chip removal. My process was basically, remove the c
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QMX WSPR Anomaly
4
I was trying out WSPR with my high band QMX with settings as depicted in the instruction manual. I had my QLG2 attached and working with the green light blinking. I had the transmit set to 4 after the hour as in the instructions, and when that time arrived, the rig kicked into transmit mode. All appeared to be going with when the display suddenly changed to read the following: 14,097,140 CW 5 0 On the next line: VK4JAZ QG62 30. And there it remained, as if stuck. After a good few minutes I shut it down as nothing appeared to be happening. Any ideas what this means?
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Everything seems good when tx 0 watts jumper in were do I start to trouble shoot?
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Broken L512 toroid.... T37-10 (Black)
2
Here's one source Bill https://kitsandparts.com/toroids.php Ron
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#qmx #SSB Firmware beta 1_01_000 release
#ssb
#qmx
Hi all, This is my experience with the SSB beta release. After much fear and consternation, I took the plunge today and installed the SSB beta firmware in a QMX Rev 1. I attempted to do a calibration on Putty, but the R and O commands would not work. This could be due to my inexperience with Putty or a failure to understand the instructions. I disconnected the QMX from my laptop and was able to run the calibration from the Hardware Tests screen on the radio. The QMX got a little warm, but the calibration was apparently successful. Afterward, I checked the CW power output on several bands, and it appeared to be normal (same output I had before the calibration). I did not put the QMX back on Putty to check the calibration curves. I tested the SSB mode with a QRPguys microphone kit and made 8 successful phone contacts on 20M. Audio and signal strength reports were good. The mic is covered by a cutdown foam windscreen purchased from Amazon, and the only mic setting I adjusted was compression set at 5. I found the best output occurred while talking straight down into the mic held about an inch from my mouth. Probably because the mic element is a setback from the vinyl cap. I have not tried other bands yet. I am mainly a CW op, but after the successful SSB implementation I may have to start making more phone contacts. I'm almost embarrassed to say it was fun! 72, Randy NR5N
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New firwware#firmware
So far everything seems to be functioning well. I have noticed that when using the swr tune function that on some bands the swr reading does not change while tuning an antenna and I have to turn it off then on again to get a new reading. This didn't happen before and would change as I operated a tuner. Randy VE3JO
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Swr meter in SSB mode
5
When I use SSB mode do the 2 m by the USB icon change? Because I'm on an antenna with 1.3 SWR but it's showing much higher when I use SSB mode.
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About calibration
2
I have a QMX built by QRP Labs. I haven't updated to the SSB firmware yet. Do I need to calibrate? How do I do the calibration process? Thanks.
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QMX quit working
2
#qmx
#troubleshooting
I have a QMX (80-20) for 12 V that I built last year. It worked fine on FD, and was used occasionally since. A few weeks ago I was running it into a dummy load. Controlled by fldigi. Power was a LiFePO through a regulator at 12 V with a 1.5 A current limit. After messing around with the fldigi settings until I got it to "transmit" into the dummy load. Output power and input current looked good. Then I got distracted doing something else. After some time I looked at the regulator and it was showing 6.1 V at 1.5 A out. The radio is on, and the display works, but obviously something is seriously wrong. WSJT-X communicates with it. I can change frequencies and modes. I looked at the back of the main board with my IR camera. The hot spots appear to be associated with Q507 and Q504. So I've blown it up, but I don't know what I did. Is there a troubleshooting guide? I've opened it up and there's nothing visually apparent. In talking this out I've sort of convinced myself that I have a shorted Q504, drawing too much current and heating up Q507. Does anyone have any better ideas? Is there any way to test this hypothesis other than cutting Q504 out of the circuit and seeing if the excess power draw goes away?
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Hi all, I finally got outside with the QMX to do a POTA activation. My objective with this setup is to have a HF kit as small and light as possible to keep in the glove box of my car for impromptu activations or in between kids sports games, practices etc. QMX is a recent kit built 20-80m version 12v and kit includes: 12 ah lithium ion battery kit built Tufteln QRP EFRW 71’ antenna Retevis mic (Kenwood jack version modified for QMX) thin paracord Weaver 12 oz throw weight 10m RG316 coax Cheap earbuds Toiletry bag from some airline Antenna was set up as a sloper with radiating end about 25’ in a tree and feed end down to a picnic table and tied to a BBQ. SWR was 1.9. Conditions on 20m were good but lots of activity from POTA and the Mississippi QSO party. I got my 10 contacts hunting since it was easy pickings. Great contacts and signal reports from all directions and I’m looking forward to many more outings with the QMX!
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beta 1_01_003 FW strange behaviors
I just got back from the Pacific NW robotics district championships where N7BIN and team were competing. There are a couple parks just off the highway near Spokane so took time for POTA on the way to/from. I noticed a couple strange things with the 1_01_003 firmware on my QMX rev 2. At one point, after powering down to swap cables, the display showed USB mode but the rig was clearly in LSB mode. I switched to LSB on 20m and everything sounded normal again. It appears that there is some way for the displayed mode and actual mode to get out of sync. When in SSB mode, I noticed that the SWR meter was swinging wildly into territory where SWR protection should have tripped, but SWR protection did not trip. When in CW mode, it behaved as expected. This was transmitting through a ZM-2 tuner adjusted for 1:1 SWR. Despite this, and the challenge of 5W SSB with a low antenna, the activations were still a lot of fun. 73, Mike KK7ER
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Image Name
Sat 8:39am
Sat 8:39am