Simple mistake: The micro usb connector was not soldered with all pins. (Units were supplied in June 2023).
I have soldered an external micro usb with some short stranded wires to the board, now it works!
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Re: QMX AGC... any progress?
I'm primarily a sound engineer by trade and have some algorithms/code from some audio dsp I've written which I'm willing to share if desired
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Re: Relationship of VDD and VCC
Hi Kees
The 1N4148 diode in the 3.3V power supply is to isolate the 78M33 when the SMPS is being used and the 78M33 is off.?
Vdd and Vcc rails are NOT connected anywhere. The "Vdd" on the IC402P/IC403P names is just a remnant of the library component! I will change it in future to avoid confusion.??
Hans,?
Yes, VDD vs VCC can get a little messy especially since the two appear to be connected together on the little IC402P/IC403P power pin schematic. My point was why is there not a 1N4148 blocking diode (or is that just a fixed voltage drop for the LDO) on both VDD power sources (the 3.3V LDO output D103 and the 3.3V output from the switcher Q111).?
Maybe I misread the schematic and VCC is not connected to VDD anywhere.
73 Kees K5BCQ
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Re: Argh QMX Q103/Q104 short
I was unsure of my ability to deal with SMD/SMT but got over it by getting a practice kit. ?It doesn’t do anything when you are done so you can’t destroy it. ?Put the parts on and take them off to your hearts content…. you will get the feel of the process.
For under $10 you’ll gain great confidence in your ability….. check your favorite source.
John KK4ITX? ?Each mistake is a learning opportunity.?
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On Aug 23, 2023, at 6:41 PM, Rich Brandt, AE8AA <richbrandt@...> wrote:
?Again, watch a bunch of YouTube videos on hot air rework.? They will tell you temperature to use and LOTS more. Comments in (parentheses) are my opinions, and I Am Not An Expert.
- Temperature (start with 350C)
- How much airflow to use (never the maximum!)
- What direction to point the hot air gun (I usually point it straight down; opinions vary.? I'll say "straight down but incline it toward an area of the board with the fewest nearby components")
- Preheating, then focusing on the component to remove.? (Patience!)
- Use of Kaptan tape or aluminum foil to protect heat sensitive, e.g. plastic parts, or to protect nearby components from the hot air stream.
- How to watch the nearby components to see when unwanted joints are being melted.
- Counting on surface tension of the molten solder of nearby components to keep them from flying away (too much airflow and they will fly away anyway).
- How to gently nudge the part while waiting for all the joints to melt (this avoids lifted pads and traces).
- How to remove the part once all the joints have melted (Tweezers!? Buy a very good tweezer).
I like Louis Rossman, so you might start here: I also like NorthridgeFix.? He's a working repair tech, not so much an instructor. Whereas this guy is kind of a klutz: If other people have favorite videos on hot air rework, please post so we can all learn. Rich
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Recommendation is not to switch inductors while transmitting. Really pretty easy to peak up noise or signal on Rx, then just use Cin & Cout to fine tune. Rarely do you need to change inductor, but if you do, turn off Tx during switching.?
--
73, Dan? NM3A
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With my QDX I always tune my transmatch with a NanoVNA before plugging in the QDX. Doing so I am sure the QDX will be plugged in a transmatch plus antenna with less than 1.5 SWR.?
73 - Pierre - FK8IH
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QCX 50W Amp w/Case, Unassembled FS
Hi Group,
I have a QCX 50W Amp with Case, Unassembled and unopened other than to look at the case parts.? $69 shipped to USA.? Please contact me directly with interest.
Thanks and 73,
Robert, WA2T
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Re: Relationship of VDD and VCC
I found some info on this article which explains all V?? cases pretty good:
73?
Barb WB2CBA
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Re: Relationship of VDD and VCC
Hans,?
Yes, VDD vs VCC can get a little messy especially since the two appear to be connected together on the little IC402P/IC403P power pin schematic. My point was why is there not a 1N4148 blocking diode (or is that just a fixed voltage drop for the LDO) on both VDD power sources (the 3.3V LDO output D103 and the 3.3V output from the switcher Q111).?
Maybe I misread the schematic and VCC is not connected to VDD anywhere.
73 Kees K5BCQ
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Re: 20m+WSPR+Loop Ant+TX without computer
The answer is: yes you can. It is part of the set-up for WSPR on the U3S. To set the clock you will need a clock that shows seconds. It can take a little practice to get close but anything less then 30 sec. should work for a few hours.? As for a loop antenna, OM0EM has a very good qrp multiband (40m-10m) magnetic loop antenna.
Paul
KD9JYV
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?? These are good, I have one I built and you can have one built by Emtech
??
????????????????????????????????????????????????? Tom, W6TOM
?
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On 2023-08-23 12:08, Gene Domenici wrote:
While waiting patiently (!) for the QMX to arrive, I am trying to fit out a go box. I've found several tuners in kit form. While my arthritic fingers can still solder, they are not up to winding toroids.
Recommendations for ?tuners that are not blinding expensive will be appreciated!
Thanks.
Gene
AC4ZY?
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Re: Argh QMX Q103/Q104 short
Again, watch a bunch of YouTube videos on hot air rework.? They will tell you temperature to use and LOTS more. Comments in (parentheses) are my opinions, and I Am Not An Expert.
- Temperature (start with 350C)
- How much airflow to use (never the maximum!)
- What direction to point the hot air gun (I usually point it straight down; opinions vary.? I'll say "straight down but incline it toward an area of the board with the fewest nearby components")
- Preheating, then focusing on the component to remove.? (Patience!)
- Use of Kaptan tape or aluminum foil to protect heat sensitive, e.g. plastic parts, or to protect nearby components from the hot air stream.
- How to watch the nearby components to see when unwanted joints are being melted.
- Counting on surface tension of the molten solder of nearby components to keep them from flying away (too much airflow and they will fly away anyway).
- How to gently nudge the part while waiting for all the joints to melt (this avoids lifted pads and traces).
- How to remove the part once all the joints have melted (Tweezers!? Buy a very good tweezer).
I like Louis Rossman, so you might start here: I also like NorthridgeFix.? He's a working repair tech, not so much an instructor. Whereas this guy is kind of a klutz: If other people have favorite videos on hot air rework, please post so we can all learn. Rich
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Re: QMX AGC... any progress?
Hi Ronan,
I had exactly the same problem, but luckily I was listening via a powered speaker at the time, so it limited the ear damage.
I have stopped using my working QMX until AGC is implemented as I don't want to experience that again!
73,
Jon G4IVV
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Re: QMX - smoke - another C107/Q108 failure
Rick wrote above: "I think the best approach here will be to rig up linear 3.3/5V supplies " Hello Rick and group, I have a similar tought on another thread in this group. Check for the message:
There already is a 3,3V linear regulator in the rig. One should only disable the "handover" from the linear regulator to the buck converter. I seriously intend to do so, at least until I understand what's up with all this happening that makes me feel rather unsure when handling the rig in so many experimental ways.
The rig is small and frail; my hands are big and clumsy... ;-)
For a 5V rail there is no such linear regulator in the rig, so one might add it somewhere where there is enough groundplane on the PCB to solder it to. I would refrain from using one of those scarry xx1117 5V LDO's needlessly having the output electrode on PIN 2 (middle pin) and the cooling tab. In case of a thermic failure, the input gets toasted directly to the output. Whoever designed this chip... (censored)
More civil linear regulators have the cooling tab connected to the ground electrode and if "melt-down" happens, the input gets connected to the ground and there might be hope that a fuse somewhere gets blown before the trace on the PCB burns out. But in most cases, the output stays safely isolated from the ugly happening.
And do not forget to connect the 3,3V regulator to the 5V rail, to avoid unnecessary loss. By doing so, there might be problems with the wake-up timing of the whole combo. As designed, the 3,3V rail feeding the main professor is alive and kicking long before the 5V rail is up. Reversing the order of wake-ups, some latch-up might occur that was not foreseen in the initial sequence. A big electrolitic cap here and there or even some sort of wise watch-dog reset-policy might be needed if wake-up gets bitchy.?
Let's try and please keep us informed of your progress. The more I think, the better I find the idea of replacing the buck converters with linear regulators, if not for good, at least for the testing period, until things settle down. But the more I think, the more I believe that, if I would succeed in replacing the buck converters with LDOs... I would just leave it stay put this way.?
It is also very refreshing to know that the buck converter boards can be tested without endangering the main professor, the one and only, the unreplaceable.
Yours friendly, Razvan dl2arl
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Re: Argh QMX Q103/Q104 short
At what temperature are you setting the hot air gun.? I have one but scared to use it.
Thankfully there is no short on my PS board.. but the components and their associated solder blobs are so very very close.
Thanks
73
Dick
W4PID
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Be aware that those type of switched-element tuners subject the transmitter to massive mismatches during switching and finding a tuning solution.? I use one but I use a QRP-O-Meter absorptive bridge between my radio and tuner;? its loss protects the TX during tuning and is then switched out.? A 6dB pad would work, too.
73, Don N2VGU?
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Is there any news of AGC being added to the QMX transceiver some time soon?
The reason I ask is that I just had a VERY painful experience using my freshly built QMX. The headphone output can suddenly jump from reasonably loud to EXTREMELY LOUD AND CLIPPED when listening to strong stations. The clipped audio is at such a high level that it can cause pain and is potentially damaging to the ear. I'm reluctant to use headphones with the radio now I know this is a possibility, which is a shame as that's how I intended to use it when out /p.....?
This is in no way a complaint. I know the radio is a work in progress and it's pretty incredible as it stands, but some sort of audio limiting or AGC really should be added ASAP to prevent further hearing damage for us poor listeners.?
Cheers,
Ronan
MM0IVR
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Re: 20m+WSPR+Loop Ant+TX without computer
Dear Bruce and all , Can I set my location info to U3S manually ?
On Wed, Aug 23, 2023 at 10:17?PM Bruce Akhurst < bruce@...> wrote: You can set the clock anytime manually and +/- a second is fine to run for a day.
The location field is an essential part of a WSPR signal? ?No one can plot your station on a map without it so transmitting will be a bit pointless :-)?
The 4 character location derived from the GPS data is not precise at all (google 'maidenhead locator') although you can upload additional information yourself to narrow it down to a smaller non- precise location?
If you sit in front of the loop you may need to so the safety calculations.? However No-one recommends running the QCX at 5W continuous.? I run mine on 9V producing about 3W and at that level and even 50% transmit operation? most EM Field safety calculators will return a 'nothing to see here'? result
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Re: 20m+WSPR+Loop Ant+TX without computer
I do all my WSPR work at 200mW or less, using SOTABEAMS for the 200mW and the QRP-Labs U4B for 27mW. ?The overall objective of WSPR is that of low power. ?200mW is almost excessive IMHO as some have indicated that that power is equal to about 4w CW. ?5w would then equal about 100w.
The only time the Grid Square will locate you with pinpoint accuracy is the unlikely event where you live in the precise center of a Grid Square.
John KK4ITX?
?Each mistake is a learning opportunity.?
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On Aug 23, 2023, at 3:17 PM, Bruce Akhurst <bruce@...> wrote:
? You can set the clock anytime manually and +/- a second is fine to run for a day.
The location field is an essential part of a WSPR signal? ?No one can plot your station on a map without it so transmitting will be a bit pointless :-)?
The 4 character location derived from the GPS data is not precise at all (google 'maidenhead locator') although you can upload additional information yourself to narrow it down to a smaller non- precise location?
If you sit in front of the loop you may need to so the safety calculations.? However No-one recommends running the QCX at 5W continuous.? I run mine on 9V producing about 3W and at that level and even 50% transmit operation? most EM Field safety calculators will return a 'nothing to see here'? result
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45 bucks in a fun kit. Got one!
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KK4ITX John
Pierre - FK8IH
Barb WB2CBA
DL2ARL
Richard Hattaway
Donald S Brant Jr
Karl