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QMX no output on 12 and 10 meters

#output #power #qmx

Emory Haines WM3M All Messages By This Member #119243 New QMX build with no output on 12 and 10 meters?? Below measured on QRP watt meter and dummy load. 20 - 4.5 watts 17 - 4 15 - 2.5 12 - 0 11 - 0 10 - 0 Checked and re-checked, did not find any solder bridges and LPF's all seem ok? Any help or suggestions would be greatly appreciated.? Thank you? 73? Emory? WM3M
Evan Hand All Messages By This Member #119246 Hello Emory, 12, 11, and 10 meters share the same low pass filter (LPF).? This would point to a problem there.? The most common is one of the toroid connections did not burn through the enamel.? This assumes that the configuration is correct.? I suggest the following: 1 - Update to the latest firmware from the QRP-Labs web page:? 2 - Do a factory reset If the above does not solve the issue, then: 3 - Verify that the LPF diode selection is working correctly.? This also verifies that the toroid connections are good, as the toroids are used to conduct the DC bias.? The LPF diodes are D508 through D513.? D510 and D513 select the 12/11/10 meter LPF.? The banded end (Cathode) should be close to 0 volts.? The other four should be close to the supplied voltage to the QMX.? This test is while receiving, not transmitting. The next steps would depend on your findings from the above.? Please post your results, including the version of the firmware. 73 Evan AC9TU
Emory Haines WM3M All Messages By This Member #119275 开云体育 Evan, Really appreciate your help and info. Will try again to make sure toroids are good and check the diode voltages. One problem I have is identifying? right solder point on bottom side of board, since it is so crowded. Will advise with results. Thank you? 73 Emory? WM3M On 3/13/2024 1:48 AM, Evan Hand wrote: toggle quoted message Show quoted text Hello Emory, 12, 11, and 10 meters share the same low pass filter (LPF).? This would point to a problem there.? The most common is one of the toroid connections did not burn through the enamel.? This assumes that the configuration is correct.? I suggest the following: 1 - Update to the latest firmware from the QRP-Labs web page:? 2 - Do a factory reset If the above does not solve the issue, then: 3 - Verify that the LPF diode selection is working correctly.? This also verifies that the toroid connections are good, as the toroids are used to conduct the DC bias.? The LPF diodes are D508 through D513.? D510 and D513 select the 12/11/10 meter LPF.? The banded end (Cathode) should be close to 0 volts.? The other four should be close to the supplied voltage to the QMX.? This test is while receiving, not transmitting. The next steps would depend on your findings from the above.? Please post your results, including the version of the firmware. 73 Evan AC9TU
Larry VE7EA All Messages By This Member #119281 Emory: before you go to all the hassle of checking the LPF's I would definitely try a simple factory reset as Evan suggested above. Have you tried that? The reason I ask is that yesterday I experienced very, very low RF out on 12 and 10m only. My QMX had been working just fine previously so I was scratching my head. Only two things had I done in the meantime between working and non-working and that was: 1) playing around testing key clicks by turning AGC on and off and 2) I mistakenly tried to tune my IC7300 (10W out) nearby my QMX while the antenna switch was set to the QMX. This would mean some SWR and RF at the antenna switch itself (not into the QMX directly). I think that perhaps the RF caused some glitch in my QMX, but I cannot be certain. At any rate, a simple factory reset cured my problem. No idea why! So try this first... Larry VE7EA
Emory Haines WM3M All Messages By This Member #119282 开云体育 Larry, I did the factory reset and reloaded latest firmware.? No change. Re did solder on both torids for 10 and 12 meters, no change. Next step is try and check the diodes as Evan suggested. Thank you? 73 Emory? WM3M On 3/13/2024 7:26 PM, Larry VE7EA wrote: toggle quoted message Show quoted text Emory: before you go to all the hassle of checking the LPF's I would definitely try a simple factory reset as Evan suggested above. Have you tried that? The reason I ask is that yesterday I experienced very, very low RF out on 12 and 10m only. My QMX had been working just fine previously so I was scratching my head. Only two things had I done in the meantime between working and non-working and that was: 1) playing around testing key clicks by turning AGC on and off and 2) I mistakenly tried to tune my IC7300 (10W out) nearby my QMX while the antenna switch was set to the QMX. This would mean some SWR and RF at the antenna switch itself (not into the QMX directly). I think that perhaps the RF caused some glitch in my QMX, but I cannot be certain. At any rate, a simple factory reset cured my problem. No idea why! So try this first... Larry VE7EA

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