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When Elecraft introduced the KH1 a year ago, I was immediately enthusiastic about the concept. A small and lightweight shortwave radio with an integrated telescopic antenna. This means that, weighing less than 400g, it can be used in any suitable location on shortwave. So I wanted to build something myself. I immediately began my own experiments with telescopic antennas for 7-30 MHz. This confirmed that a counterweight is absolutely necessary. This wire, which is a quarter of the wavelength long, contributes significantly to the radiated energy. So the idea arose to forgo the telescopic antenna and experiment with end-fed wires twice the length. Of course, it makes sense to stretch the wire as high as possible. But I also got respectable reports with EFHW lying on the ground or in bushes. In this place the antenna may detunes itself, so a tuner is necessary, as well as the standard 1:64 transformer (Unun). The tried-and-tested resonance circuit (Fuchs Kreis) performs both tasks. Once the antenna issue was resolved, QRP Labs brought out the QMX. The ideal TRX for my projects, and now even capable of SSB. Now all that was missing was a suitable housing with an integrated battery and a speaker with an amplifier. Then a paddle for CW as a contactless touch key directly on the device. And the QMX Carrot was finished. But it wasn’t that simple, because everything had to be as small and light as possible. It now weighs 340g and measures 15x8.5x3.0 cm. I’m happy with that. 73 Chris https://youtu.be/0kksiWVOtnQ

I am just having some fun in the King of Spain contest . AGC is giving me some trouble. apart from vy strong stns overpowering the Rx the AGC is too slow to recover. Can anyone direct me what settings to change to ge a quick AGC ? - Martin DK3UW

Hi, I’ve had my QMX+ for a number of months and had tested the then beta now regular SSB firmware with good results except pretty low output power in SSB. As I had never gotten around to fine tune the LPFs when building it I decided this was the logical next thing. So I fiddled with spreading and compressing turns on the toroids and managed to get all bands to between 4 and 5w output for CW except 160m that was already at 6w. Running 12.0v input and build for 12v Being happy with results I then first tested resetting to factory defaults, and then tested SSB output power. Still max 2-2.5w according to the Bird. I then decided to run the SSB calibration again. Worked fine til perhaps 12m or 10m phase. I then heard some terrible noise from the speaker and saw the QMX crashing with all blocks in the display and turning itself off. I tried powering on again, but won’t start now. Just blank display and current protection on PSU kicks in due to over current. I suspect maybe finals are fried with internal short as result? Jonas 7 maj 2025 kl. 23:12 skrev Stan Dye via groups.io <standye@...>: ? On Wed, May 7, 2025 at 01:38 PM, Wiggle Pig wrote: It’s D503 and D504 These are placeholders for diodes that could be placed across the BS170 outputs, as was commonly done with QDX. Hans included them in the design, but has not encouraged installing the diodes, which he believes are unnecessary for QMX. They may suppress spikes, but they also add additional capacitance to the PA, which may affect it adversely in other ways. There were many posts on this list regarding this topic a year or so ago. Stan KC7XE

I have not been able to see on the initial first power up any means of loading firmware on my QMX+ radio. I was able to see some evidence of 2 files on E drive which is the USB drive on my computer by shorting AUX2 to ground before power on. The two files in E drive are file 1_00_027.QMX and EEPROM. EEPROM is an empty file.. Have I missed something here or do I have a bigger problem that cannot be solved easily? Any help would be greatly appreciated. Thank you, Ron W6ZQ

Can one of the QMX+ builders tell me: 1) the dimensions of the main PCB 2) the dimensions of the front panel PCB After building and using the terrific little QMX, I am considering building the QMX+ but using my own enclosure. Thanks! 73 Robert VE7ZN

Can anyone provide an example of how high the mic input noise level is in the terminal tool with without the mic attached in firmware 1.0.2? I see 3 grey bars in the mic test with the gain set to +50db, which looks significantly higher than Hans' from the manual. I'm trying to determine if I have an internal noise issue with my unit.

I have corrected all the issues with my enameled torroid soldering joints, so those look reasonable now on all bands. That said, I have no power whatsoever when pressing "T" on the diagnostics screen. I am using 3 cell LIPOs charged to 11.9vdc (checked after charging with multimeter) for power. T501 wound for 12v. - Initial startup was at 7v, just to be safe. No issues or magic smoke so slowly raised voltage to 12V with no issues. No pops or anything else. - Checked T507 by removing and testing, then reinstalling. - Removed and rewound T501, RWTST, to eliminate concerns of over twisting the wires. - Rewound T401 and checked for continuity on the 3 pairs, then installed it. - T502 has continuity and the correct amount of wraps. - The dummyload I am using is one I purchased along with the kit. Assembly was enjoyable and it measures 49.5 ohms. When I press "T" I get 0.0 power. I checked the SWR protection set it higher, and restarted the radio, but still get 0.0 on the diagnostics screen. I then turned the SWR protection completely, then restarted the radio and still 0.0. The power transistors DO get slightly warm, but not suddenly. From what I can tell, everything is as it should be, but I'm still getting no power to the dummyload. I have no actual antennas yet, but should have one completed in a couple hours. I checked several patch cords (between radio and dummyload) and they all are working correctly, but still no power. What should I be checking now? Is there a test procedure for this specific issue? There has to be others who have encountered this before... Thanks again, btw... Ahand59

All of my I/Q sweeps look textbook, with the exception of one...160 meters, where the I&Q are way off in both offset and amplitude. Mind you, in 35 years I've not had a single 160m contact, so addressing this is not a high priority! Still, the perfectionist in me wants to get it sorted out at some point. Here is the offending sweep. It seems like the trifilar wound toroid is the usual suspect in cases where multiple bands are involved, but like I said, the other bands look great with nice sine waves (a little messier as the frequency goes up, as Hans mentions in the build manual) with the perfect 90° offset. Anyhow, please take a look and if you have any thoughts, please share them! Bandpass filter? FWIW, power output on 160m is excellent, maybe too good at almost 6 watts.