Re: Intermittent QDX transmit failure on one band
Leigh,
Solder joints can behave like this. Imagine surfaces pulling apart as they cool and shrink.
With focus on the 20m LPF, I suggest checking the inductor leads first. A poor joint that is the result of inadequate enamel removal can wreak havoc.
Next comes the capacitor solder joints, with emphasis on the ground leads. Good solder joints need heat and the inner ground? planes suck that away from the joint.
If after all that you suspect something is wrong with PIN diode switching, a voltmeter and Hans' excellent circuit operation description comes to the rescue.
I think the most likely is the first possibility, inductors,? though.
JZ KJ4A?
I have a QDX (board rev 3a) for 80-20m that I'd used successfully on a number of outings. On a recent SOTA attempt, however, transmit on the 20m band stopped working after about 15 minutes. I switched to 40m and that transmitted fine. But even after rebooting a couple times, I could not get transmit on 20m to work again.
When I got home and put the QDX on the bench, it worked fine again to transmit on 20m. Troubleshooting intermittent failures is fun!
On the day of the 20m transmit failure, the temperature was cool out, maybe about 45° F (7° C). That was the coldest conditions I had tried operating in. So I'm wondering if there's a small crack in some component that caused an issue when cooled, something that's part of the diode band-switching circuitry.
Which components should I focus on as the most likely culprits for an issue like this?
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So grateful for Jeffrey Moore, W1NC, who can figure out where we went wrong with our QRP Labs kits. Admittedly I do not quite have the tech chops, in spite of my enthusiasm for kit building. But Jeffrey got my QMX working and totally explained in detail what all he fixed. Here's the kicker: all Jeffrey asks for is a donation to cover parts/labor/postage, which he leaves entirely up to you. What an incredible service he does for those of us who need the help! Kudos to Hans for these ingeniously designed kits, and to Jeffrey who can solve the mysteries we sometimes create! Eric AC6NT
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Intermittent QDX transmit failure on one band
I have a QDX (board rev 3a) for 80-20m that I'd used successfully on a number of outings. On a recent SOTA attempt, however, transmit on the 20m band stopped working after about 15 minutes. I switched to 40m and that transmitted fine. But even after rebooting a couple times, I could not get transmit on 20m to work again.
When I got home and put the QDX on the bench, it worked fine again to transmit on 20m. Troubleshooting intermittent failures is fun!
On the day of the 20m transmit failure, the temperature was cool out, maybe about 45° F (7° C). That was the coldest conditions I had tried operating in. So I'm wondering if there's a small crack in some component that caused an issue when cooled, something that's part of the diode band-switching circuitry.
Which components should I focus on as the most likely culprits for an issue like this?
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QCX WARC Party - July 2024
Hi all,
?
next Monday, July 15, is the next QCX WARC Party.
?
See 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 ...
?
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 July 29 ! ?
?
73 es GL,
Luc ON7DQ
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WSJT-X has a band/freq selection window lower left. These are click selectable on Windows 7 on up. Click on your choice and radio instantly displays the freq. I am sure you already know this but I state it to make sure we are on the same page of the same book!
--
73
Karl
KI4ZUQ
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Could someone provide a circuit description for Q202 and Q201 in the Driver_Bias part of the schematic?
I'm also have a problem setting the bias on Q207 (Q208 is OK). I increase the pot to approximately 90 percent, at which point, it suddenly jumps to an excess bias amount. Way too touchy to set it to +125 mA. Could I have a bad pot? This happens regardless whether I set Q207 first, or second.
Thanks a bunch!
- 73, John, N0TA
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Re: First QSO in 45 Years! FT8 on 20m with QMX
That is fantastic, welcome back. You need to try Parks On The Air. This is a real good way to get your CW speed up. It's a short exchange and lots of fun. POTA has a great web site.
On Sat, Jul 13, 2024 at 11:53?AM WB0ZJJ-Alan via <alanmcdonley= [email protected]> wrote: 50 years ago the great hams of Salt Lake City helped me to get my ticket, build/checkout an HW-101 100 watt radio, and get on the air with CW at 13WPM and SSB. After about 5 years on the air, I sold all my gear and left amateur radio behind (but kept the ticket renewed for sure).
TODAY! First "QSO" in 45 years. Since my CW copy is slow with frequent missed characters, I used WSJT-X in FT8 with my newly built QRP-Labs QMX rig on 20m for my first contact attempts.
I strung up a 20m EFHW about 5 feet off the ground, and checked the SWR. Not great - between 1:2 and 1:3 but what the hey, we'll see what happens.
I sent a CQ QRP and checked fskreporter.?I was getting out!, and was even more surprised when someone actually responded with my call. WSJT-X noticed the reply and auto-sequenced the QSO - Pretty cool.
240713_135645 14.074 Tx FT8 0 0.0 1604 CQ QRP WB0ZJJ EL96
240713_135700 14.074 Rx FT8 -18 0.1 1603 WB0ZJJ WA6GXQ FM06
240713_135715 14.074 Tx FT8 0 0.0 1604 WA6GXQ WB0ZJJ -18
240713_135730 14.074 Rx FT8 -18 0.1 1603 WB0ZJJ WA6GXQ R-11
240713_135745 14.074 Tx FT8 0 0.0 1604 WA6GXQ WB0ZJJ RRR
240713_135800 14.074 Rx FT8 -14 0.3 1603 WB0ZJJ WA6GXQ 73
I entered the QSO into??as my first logbook entry and hope to see it confirmed.
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Re: QMX+ is completely dead after unsuccesful firmware update.
When you force firmware update method be sure you are connecting between AUX2 and Ground. I looked at the?picture and connected between the two red arrow points. Be sure you are connecting between either of the RED arrow points and either of the GREEN arrow points. If you go between the two red arrow points your computer will give you the error message. I and a friend did the two red arrow points..duh!
Mike WA8UOC
I tried to update the new firmware 1_00_020 with a laptop.?
The USB connection was a little bit strange as the laptop did not expand the QMX device icon to show it?s contents.
I ignored that strange behaviour and dragged the firmware file to the QMX device icon and it seemed to me that the file transfer started.
But immediately thereafter, the laptop showed a message "USB connection aborted" or something like that.
QMX did not react to the power button, (or maybe did, but the display did not activate).
I tried to use the AUX - GND wire method to force the QMX to firmware update mode, but no success. The laptop did not detect the QMX.
It is obvious that there was some problem with my laptop. The laptop was running with battery power.
Now using my desktop PC does not help, the PC does not detect the QMX.
What to do?
?
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Re: Hermes Lite 1 : RM Italy BLA 350 : QRP Labs 10W Linear
Don,
Its 350W and 1db compression is likely above that.
if he gets 260 hes less than 3db down. If the QRPL amp
is run at 15-18V it will give you more I usually see 11W
at 13.6V and at 16V more like 15W. Also the amp at
20V will produce 25+W. So there is margin there.
That and most devices for that power level might tolerate
20W before becoming fuzes. The BLA350 has a input
sensor and will trip if over 13W.
Myself I'd check the BLA for input attenuator as the apparent
gain is about 14db. Two cases for that, bipolar devices that
would be typical, or Mosfet with attenuator. Looking at the
schematic it has Mosfets and a input attenuator.
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
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First QSO in 45 Years! FT8 on 20m with QMX
50 years ago the great hams of Salt Lake City helped me to get my ticket, build/checkout an HW-101 100 watt radio, and get on the air with CW at 13WPM and SSB. After about 5 years on the air, I sold all my gear and left amateur radio behind (but kept the ticket renewed for sure).
TODAY! First "QSO" in 45 years. Since my CW copy is slow with frequent missed characters, I used WSJT-X in FT8 with my newly built QRP-Labs QMX rig on 20m for my first contact attempts.
I strung up a 20m EFHW about 5 feet off the ground, and checked the SWR. Not great - between 1:2 and 1:3 but what the hey, we'll see what happens.
I sent a CQ QRP and checked fskreporter.?I was getting out!, and was even more surprised when someone actually responded with my call. WSJT-X noticed the reply and auto-sequenced the QSO - Pretty cool.
240713_135645 14.074 Tx FT8 0 0.0 1604 CQ QRP WB0ZJJ EL96
240713_135700 14.074 Rx FT8 -18 0.1 1603 WB0ZJJ WA6GXQ FM06
240713_135715 14.074 Tx FT8 0 0.0 1604 WA6GXQ WB0ZJJ -18
240713_135730 14.074 Rx FT8 -18 0.1 1603 WB0ZJJ WA6GXQ R-11
240713_135745 14.074 Tx FT8 0 0.0 1604 WA6GXQ WB0ZJJ RRR
240713_135800 14.074 Rx FT8 -14 0.3 1603 WB0ZJJ WA6GXQ 73
I entered the QSO into??as my first logbook entry and hope to see it confirmed.
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Re: QMX S9+ noise on receive
My I/Q diagnosis looks much worse. I can see the 90 deg phase shift clearly but the signals are extremely noisy. My receive sensitivity seems to be fine though. I compared it to my K3 with an antenna switch and it’s very close with the K3 having a slight edge. That said, the receive audio is pretty nasty compared to my silk smooth K3. Listening to CW on the QMX for half an hour gives my a huge headache.
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Re: QMX S9+ noise on receive
James,
Check that you have properly removed the enamel insulation and have a good solder joint at the 60 m end connection to L401.
JZ
My 60-15M QMX hears 1 microvolt easily on 40 through 15 but needs an S9 signal or better on 60 meters. I'm not going to operate on 60 meters so I wont be fixing it but wanted to post this in case it helps.
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Re: QMX+ is completely dead after unsuccesful firmware update.
The USB cable is OK.
The problem is in the QMX:
What happens when the firmware update process is interrupted?
Is it possible that the firmware gets corrupted so that there is no working firmware?
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Re: QMX+ is completely dead after unsuccesful firmware update.
Have you tried a different USB lead?
73 John
toggle quoted message
Show quoted text
On 13 Jul 2024, at 15:29, holoma47 via < matti@...> wrote:
I tried to update the new firmware 1_00_020 with a laptop.? The USB connection was a little bit strange as the laptop did not expand the QMX device icon to show it?s contents. I ignored that strange behaviour and dragged the firmware file to the QMX device icon and it seemed to me that the file transfer started. But immediately thereafter, the laptop showed a message "USB connection aborted" or something like that. QMX did not react to the power button, (or maybe did, but the display did not activate). I tried to use the AUX - GND wire method to force the QMX to firmware update mode, but no success. The laptop did not detect the QMX. It is obvious that there was some problem with my laptop. The laptop was running with battery power. Now using my desktop PC does not help, the PC does not detect the QMX. What to do?
?
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Re: QMX S9+ noise on receive
My 60-15M QMX hears 1 microvolt easily on 40 through 15 but needs an S9 signal or better on 60 meters. I'm not going to operate on 60 meters so I wont be fixing it but wanted to post this in case it helps.
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Re: QMX+ Power Supply boards problem
#qmx
Dear Dan,
I am in about the same position as you are... I did find a short under the GPS Module where the jumper for the VDD power was touching the
GPS antenna jack. I have been inspecting my board for shorts and opens but so far... Have not cleared the faults. If you can get it to load
the software .... You can use Putty to look and the hardware diagnostics. That will give you what the software sees. Mine says the 5V power supply is high and the 3.3V power supply is about 2.9V on the linear power supply. I can't seem to go any farther than that. I have changed the power supply boards twice. Not finding any bad solder joints and no other shorts. My board has an intermittent short on the VDD bus somewhere... But can't find it and all solder connections look good. Running 8Vdc on input voltage board draws about 200ma when turned on and nothing until I hold the power on button (Long press). Right now I don't know exactly what else to do. My 3.3V power board gets warm to the touch but so far no fire.
My front panel display has never lit up but I see the top row of digits are squares and nothing on the bottom row. Voltage to the readout but nothing but squares on it. Contrast doesn't seem to do anything but make them disappear. Woe is me. I may give up on this one and try again. My problem may be a board short.
Take care and have fun.
73 Dave WA5DJJ
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Re: QMX+ Power Supply boards problem
#qmx
Thanks Ludwig. I've started looking at it. Let me see what I can find out.
--
Dan Reynolds -- KB9JLO
<><
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Finally getting the qcx-mini broke in for summer camping season. One thing I have been noticing it the AGC has a remarkable pop on the first character sent from a strong station. With AGC off there is no problem other than having to ride the gain knob.
The adjustment on my AGC is very light. I set it up so that it has a very light action. This is because I sometimes share the audio out with a signalink. If I set it per Hans instruction, attenuation is too much to allow sharing of the signal out. So its barely adjusted above the minimum stop.
Any ideas appreciated.
--
regards,
Bryan, N0LUF
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Have a look here David,
I use a 6 band u3s running on 12v into a bank of 5v regulators, power out from 1w to 0.1w, can be heard worldwide, also lots of different modes available, also running a gps to set time and keep it on frequency.
Good bit of kit.
2200m: 0.137400 – 0.137600
600m: 0.475600 – 0.475800
160m: 1.838000 – 1.838200
80m: 3.570000 – 3.570200
60m: 5.288600 – 5.288800?
40m: 7.040000 – 7.040200
30m: 10.140100 – 10.140300
20m: 14.097000 – 14.097200
17m: 18.106000 – 18.106200
15m: 21.096000 – 21.096200
12m: 24.926000 – 24.926200
10m: 28.126000 – 28.126200
6m: 50.294400 – 50.294600
4m: 70.092400 – 70.092600
Andy
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.
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Re: QMX S9+ noise on receive
Bruce, Another way you might be suffering high noise while having acceptable sweeps is if there is a problem with IC401, the stereo DAC that drives the headphone amplifiers.
Finally, sitting between the PCM1804 and the CS4334 stereo DAC is the MCU. All the digital numbers that represent audio signals pass through the MCU, communicating in and out using the I2S serial data bus. It is possible, though less likely, that something is wrong along that path.
All of the above requires an oscilloscope at a minimum, and perhaps even a logic analyzer to resolve.
On this forum I have seen virtually no reports of CS4334 problems or of I2S data corruption. There have been some MCU failures, but usually they are not subtle ;-(
The PCM1804 has been something of a problem child in QMX and several of us are trying to suss out why that is. My bet is on the PCM.
JZ KJ4A?
Hi Bruce.? I'm listening to 15M CW right now and the band is full of CQ TEST. SKCC contest, I think.? So, AFAIK, my mid-band QMX is working just fine.? I've had QSOs on every band where my antenna is resonant...
John's assessment is probably spot on.? But a little noise on the ADC I/Q diagnostic doesn't seem to have impaired my QMX, for whatever reason.?
.rr
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Leigh KG7WED
ON7DQ Luc
Karl
WB0ZJJ-Alan
Dan Reynolds
M0RON