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Hey everyone, I recently bought a ready-assembled QMX after my DIY attempt didn’t quite work out (let’s call it a “successful failure” ?). Funny enough, I had no issues building the QMX+, QDX, or even the QCX Mini before. With the assembled QMX, I’m getting a continuous tone every 700Hz on the 40M, 17M, and 15M bands. All the other bands are working fine. Here’s what I’ve tried so far: Factory reset Upgraded to the latest beta firmware Tested with different batteries and power supplies Swapped USB cables Connected to both a laptop and an iPad running iFTX One key observation: these unwanted tones only appear when an antenna or dummy load is connected. Without any load, the issue disappears. That makes me lean toward a hardware issue—maybe something in the PA section or related to RF feedback. I’m attaching some test results in case anyone spots something I may have missed. The timeslots on the JTDX without noise is when I disconnected the dummy load. Any thoughts, suggestions, or similar experiences would be greatly appreciated! Thanks in advance! DL7EDU - LU5VQV
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QM
Stan, Thanks for the tip on using the QMX at 1/4 power to set the tuner after a band change. That works and now I don't get the dreaded "S" after the frequency. I don't intend to use the QMX in the shack but I wanted to do something to see if it worked before I introduce more variables in the field. Probably use a Wolf River Coil in the field. I also have an EFHW to try. I am learning more each day. Jim W0RLD
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QMX+ with 100 amp/hour lithium iron battery
26
Just about to finish my QMX+ build and I have a voltage question. The kit was built for 12 volts. I have a 100 amp/hour lithium iron battery for vhf base station emmcom backup. At full charge, its just north of 14 volts. Would it be wise to install a buck converter in the battery box to limit voltage out to 12 volts for the QMX+? Thanks in advance - I really don't want to fry this little gem. -- Jim, W7EZN 73!
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Torrid wire
2
What type of wire is used on the torroids? I want to rewind some but I don't know where I put the extra.
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After assembling a QDX rig for a local ham I received a couple of the QDX PA mod PC boards made by WB2CBA which have the FDT86256 mosfets. They have a max voltage of 150V compared to the 60V of the BS170. Since I like to experiment I decided to try and adapt one of the boards to my QMX+. I filed off the two "tabs" opposite the mosfets being careful not to file off any of the traces. It fit perfectly where the BS170's were. After some testing it seems to work well. My QMX+ is presently wired for 9V and I have a Buck-Boost converter stuck on the back set at 10V so I can use any battery I like from 5V-30V. On 80m-30m I can easily get 5w with the 10v input. Since I like to "play with fire" I plugged in my 12.6V battery and got 6.5w-8W on the lower bands. The mosfets stayed very cool....into a dummy load. While playing on FT8 with my Hexbeam and low SWR sometimes the finals got warm and actually got pretty hot on some of the higher bands but kept work fine. If anyone else out there can or wants to give it a try, especially if you have the proper test equipment please let me/everyone know what you found. The info for the PC boards are here... https://github.com/WB2CBA/QDX-PA-MODIFICATION/blob/main/QDX%20FTD86256%20PA%20Modification%20Story.pdf Tim - K5DEZ
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QMX+ Supply question
3
I have built my QMX+ for 9 volts. When I run the TX test from the putty window, it shows the TX voltage as 7.5 volts. This is presumably the voltage at the source of the modulator FET as measured by the ADC_PA port on the schematic. With my QDX, a 9 volt build puts close to 9 volts at that point in the circuit. The question is, can I run my QMX+ supply voltage higher than 9 volts for FT8/CW operation? What about SSB? Tony AD0VC
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ssb power drop off - fixed i thank ???
3
raised the ssb drive, all looks to be working as normal.... can anyone tell me what their ssb drive is for me to compare ? thanks to all that have responded and to all on this great group :) -- 73 ChuckR
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File /QMXplus_Hardware_Mods_V1.0.pdf uploaded
#file-notice
The following items have been added to the Files area of the [email protected] group. /QMXplus_Hardware_Mods_V1.0.pdf By: OE1IRA <stangeler@...> Description: Some hardware modifications, including: TN0110 FETs, LP+BP filter retuning, better diodes for the SWR/power detector and more
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QMX+ 'tune up'
2
Just wanted to leave a compliment for Jeff, W1NC, on a recent set up of my radio; so thorough and such a detailed list of what was done! Great to have folks like Hans, Jeff, and others in this group always willing to help unsnarl various issues. Thanks also to Hans for a fine product that just keeps getting better. 73, Dick, K5AND EM00xh
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ssb power drop off
4
ssb power had been showing abt 4.6 watts on digital watt meter. with no sign that something was amiss the ssb power has dropped to .9 watt. the digi mode power is still showing abt 4.6 w. i reinstalled the ssb firware but the ssb power is still really low. any thoughts or guesses and what say you that i could possible try !!!! ? thanks -- 73 ChuckR
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I just wanted to activate JS8 and cont get it to transmit. WSJT-x is working so basically I would thing the setting is ok JS8 is decoding so that looks ok as well i tried to play with modes with no change. Any Ideas ? Martin DK3UW
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Ham Radio Crash Course is building a QMX tonight!
3
Popular American West Coast Youtuber is building a QMX on stream tonight at 8 PM EDT (US East Coast Time). Seems like it might be of interest to the group. https://www.youtube.com/watch?v=7iOY1p7flPU&lc=Ugw2vcdWfQbWKblZc_R4AaABAg.AGomNNvKyjwAGpN0n8kGVR
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Hi All, I just recently finished my QMX mid band kit and on powering up, my computer does not see any usb device. I have tried a computer running Windows 10 and another running Linux. I have tried multiple combinations of plugging or having the device unplugged before power on. I have been using a voltage and current limiter with a battery pictured below, limiting voltage to 7V then 9V (to see if that would make a difference) and limiting current to 250 mA. In the pictures, you can see the device off then when I turn it on, the V out goes down slightly and there is a 170 mA current draw. Thanks all for any suggestions, Andrew
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60-15m QMX wound inductor attachment question
8
Hi All, I'm very new to building kits, and radios in general. Working though my 60-15m QMX and I am at step 2.12 where I am winding and attaching L511, L506, L512, L508, L513, and L510 and I wanted to confirm that winding number 0 should go on the outside through hole for each inductor and the final winding should go through the hole that is closer to the center of the toroid? This seems to be the way it should be, following the instructions from L502 but I wanted to be sure since I have not been able to find a clear picture online showing how these inductors are mounted and there are not explicit instructions in the manual for these specific attachments. Thanks in advance! Andrew
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QCX WARC Party - April 2025
Hi all, Tomorrow, Monday April 14, it’s again time for the QCX WARC Party. So get out that QCX/QDX/QMX, and put it to good use. Remember : the QCX QSO parties are a celebration of the QRP Labs rigs, but you can also participate with any other (qrp) rig you have. Check https://www.qrp-labs.com/qcxmini/qcxwarc.html for all info Join the discord page in the #qcx-qrp-operation channel to post your QRG (and mode) or exchange other info, complain about the weather ... or just have a chat with other QRP Labs friends ... https://discord.com/invite/GdZzmhuU8p Also check out this new website by Tom,DK3DUA https://www.hamserver.de/qcxparty.php Report your results as a reply to this message (please don't start a new topic, then it's all in one place). No scores, no prizes ... just plain fun. The next QCX Challenge on the regular bands will be on April 28 ! 73 es GL, Luc ON7DQ
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Hi Everyone, I have a QCX mini that has been working perfect for the past 2 years. With all the QMX SSB developments, I have not powered it up for quite some time. Today, however, I decided to give it a spin. If you look at the picture, I encircled the lost lines on the LCD (1 horizontal and 1 vertical). The radio works perfect. What I have done: 1. Factory reset the radio - did not fix it. 2. Reflowed all the connection from the LCD sister board as well as the connectors on the main board - made no difference. So before I start really stripping things, have anyone else experienced this and what was the solution. 73 ZR6TM Timo
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How to turn QMX-Hi into QMX-LOW band?
3
#qmx
Hi dear All, I have a _not assembled_ QMX-HI kit (20, 17, 15, 12, 11 and 10m) version . I changed my mind, I decided to build a QMX-LOW (80, 60, 40, 30 and 20m) version. For this purpose, will it be enough for me to buy aditionally the set of band-specific parts for the QMX low-band option (80-20m, product Code: QMXLOW)? It includes all capacitors, all powdered iron toroids, wire, and ferrites (binocular cores and toroids). Are the QMX board and board-mounted SMD components the same for all versions? Thanks in advance for your advice and recommendations, Wlado 73
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MOD Board
4
Hi all, is the circuit board availble to purchase and where to order? This would possibly solve a problem with my starion setup. -- 73 ChuckR
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GPS module GY-GPSV3-NEO wont change baud!
3
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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What do people do for building or sourcing custom inline fused power cables?
8
#parts
#power
#supply
#12v
Hi all, I'm a new ham trying to build a power supply cable like this for my QDX or QMX+ to use my existing battery in the field: 12.8V LiFePO4 battery > 18AWG cable w/ ring terminals > inline home-brew buck converter > 18AWG cable > fuse (1.5A?) > 18AWG cable > 2.1mm barrel connector The part in bold is what I'm having trouble finding an obvious solution for. Is there a way hams typically build such fused cables without a whole lot of extra splicing? I feel like I'm missing something because I don't see much discussion about this or any pre-made assemblies like that. Sources for such an assembly would also be appreciated. I saw this thread but ordering from UK to US and cutting off the Powerpoles isn't a good option. /g/QRPLabs/topic/95334671#msg95573 Here's some background discussion on the buck converter build we're doing if anyone's interested in that. Thanks, Mike
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Image Name
Sat 8:39am
Sat 8:39am