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Bill, I just had an issue with what I thought was a misplaced cap on a kit I was building. ?After I removed the cap I heated up the solder on the board and slapped the board on my workbench….. out came a little bit of solder each time I did it. Eventually I was able to remove enough solder to reinsert the same cap…. I had made a mistake and THOUGHT I had put the wrong cap in the wrong place…. I misread the instructions and was correct the first time. Ha! ?Heat and slapping the board on a hard surface helps. Adding some more flux helps also.

Ok, I have built almost a dozen of Hans's kits and this is the first time I put capacitors in the wrong spot. ?It is the new qmx+
I have removed the misplaced caps, but they are in bad shape. ?I used some flux and soldering wick to clean it up, but the hole
is full of solder. ?Any ideas how to fix this without ruining the board. ?And I will need some odd capacitors too. ?thanks. ?have a laugh on me.
At least is was at the beginning of the build.

72

May not be the your issue, especially if your tests were using a know good dummy load .... but .....

Link does not work...
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73
Karl
KI4ZUQ

If you just plugged the QDX into the computer, then from the last line of the log file, the name of the serial device you need is:

?

/dev/ttyACM0

On 08/07/2024 03:09, Larry Christensen via groups.io wrote:

I unplugged the gps on the QMX+ and both clock displays returned to normal. It is acting like the gps in the QMX+ is acting as a transmitter not a receiver and is blocking to other two GPS receivers.

Larry,

I have had a similar effect a few days ago.
I have used 4 co-located GPS antennas working with 4 different radio projects. All have worked properly for many months.

I then moved one of the setups using a different GPS antenna, again mounted within 6" from the others.
Next day I noted that all GPS units were not locked. Recorded frequency variations indicated this had happened intermittently overnight. After a while all locked again.
During the day I noted that occasionally all 4 lost lock, I was suspecting QRM (Local BAE Radar test site) but nothing around 1.5GHZ.

Moving the new antenna 6" further away restored lock on all.

So far I have not discovered why this happened.
I have not reproduced the fault by moving the antennas closer.
I was wondering if the new antenna was oscillating or whether leakage from digital circuits was passing up an antenna cable.
I think it unlikely the a GPS receiver would oscillate.
Maybe a weird phasing effect involving the placement of antennas? Exact original cable runs and antenna placement not recorded and have moved.

(None of the GPS are QRP Labs, the 4 not directly connected to any QRP Labs modules each discipline a frequency reference. Two Progrocks and a QDX are involved. I do also have a U3S with GPS but did not remember so did not check that.)

73 Alan G4ZFQ

The soundcard works only when the qmx is powered on. It isn't usbpowered.
And, as in all other "no tx", is the audiovolume at maximaum?
Not to forget, turn into digimode.

my Parameter under Linux Mint

73 Bernd

Hello matjaz
Have you activated the Dailout in your group settings.
A reboot must then take place.
I use QDX hig and Low Band under Linux Mint

For searial connection
1. Plugin
2. 'sudo dmesg' and you'll find the right device

Or: a way for unique naming: (not sur it will have qmx or qdx in the name)
unplug and check whats inside: /dev/serial/by-id/*.
plugin and check again. the new one is yours. This name will never change, unlike ttyUSB*

And don't forget the modemmanager must be removed, what isn't easy, sometimes,? as should be.

Hi Ludwig
Sorry for the delay but family matters over the weekend.? I've done many measurements and am reasonably certain either the 'scope or the probes are limited in bandwidth.? See my notes and findings below...

Could you check

1. the region of the BS170 for unwanted things, (See pix attached.? All pads and soldering look fine and check ok)
2. T501 and the area around,? (see pix attached.? I rewound this in case I had made a mistake but the original looked fine and the replacement performs the same)
3. the PIN diode system of the LPF section,? (I tested each diode, checked the configuration and voltages at each point.? All are per the document.)
4. the G, S and D voltage at Q508 for RX and TX,? (TX G=0, D=10.6, S=0; RX G=3.3, D=0, S=0)
5. the frequency response of your oscilloscope with the actual probe (e. g. checking a fast clock signal from the QMX).? (I used the three CLK's 0,1&2 with both probes and got the same results across 1.8MHz to 50MHz.? All 3 signals produced the same waveforms on each band.? Good square waves on 1.8, 3.5 and 7MHz and the waveform got progressively more round until at 50 MHz the signal was a sinewave.? I think the probes may be part of the problem.? I have ordered a better quality (bandwidth) probe.?

For No 1 and 2 it would be fine to show detailed photos. (Pix attached) For No 3 you will find information reading this document from the QRP Labs Wiki (section PIN diode switching). It's for QMX but simple to expand for QMX+.

It would be also fine to remove all BS170 and check the signals from IC503 for different bands.? I removed all BS170's and made the following measurements:

Voltage measurement p-p (with scope)				?	?	?	?
?	?	1.8MHz	14MHz	28MHz	50MHz	?	?
Q503,505 gates		?	5V?	4.2	1.3V	IC503 outputs
Q504,506 gates		?	5V?	4.2	2.0V	No FETs in circuit	?
IC501 pin 4		3.8V	3.5V	3.0V	2.4V	?	?
IC502 pin 4		3.8V	3.5V	3.0V	2.3V	?	?
?	?	?	?	?	?	?	?

The step next is a visual check of the capacitors from "+12V" to GND and from VCC to GND.? I checked all caps on both rails visually and with a DMM where possible and all appear ok.

To get a better impression of your system:

• which power supply do you use? See pic
• which dummy load do you use?? See pic

Apart from having to replace Q507, I'm unsure how to proceed.? Maybe a better probe will give more meaningful readings/measurements.
Regards, Greg.

Larry,

That does sound like your GPS unit is defective. If you have an appropriate USB to serial cable , you could check it out stand-alone on just a PC. The pinouts are easy enough, but you need to make sure you power it with 3.3v and not 5v (I think I remember it as 3.3v). I have connected several GPS units to my PC in just this way and the data is just serial text streams you could see in a terminal window. But you would need that cable to test it. There isn’t much you could do to repair it if it were defective anyway, so I’m not sure it would be worth it if you didn’t already have the necessary cable.

Sorry I don’t have any better ideas.

73, Gregg W7GRM

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? I have a new QMX+ that was ordered as built, with the GPS Option and built for 12 volt operation, installed the 3 volt battery and then went to test.

? Using a small cheap Thomson laptop with Win 10 that was bought with idea it would only be used for WSPR or FT8 in the field. Laptop has 4G of Ram and 60G SS Drive, 30G available. I also run a GPS program, use Com3 for the QMX+ and Com4 for the GPS. This has all been used with a QDX.

? I'm also powering the QMX+ off a 9 volt supply to give some protection to the finals.

? I tried a test, I wanted to see how much power I put out on WSPR running at 9 volts using a 50 ohm load. What I intended to do is go from 160 to 6M one band at a time using the TUNE function in WSJTX.? Not? to be.....

? I can get 40, 30, and 17M to work, 80M worked once. If I select 40M I need to power the QMX+ down and also close and WSJTX application then power the QMX+ up FIRST and then run the WSJTX program and now I get RF out. BUT.... If I go to another band, say 30M, the QMX+ screen changes to that Freq, I get a TX screen indication but NO RF. Leaving the Freq selected that changed if I power cycle? the radio and reload the program now the 30M freq comes back and I can get RF power. Go back to 40M, the Freq changes and I get a TX screen indication but NO RF.

? NO RF OUT on 160, 20, 15, 12, 10 or 6M, tried various combinations, the QMX+ does show the Freq and gives a TX indicator.

? Also, the QMX+ MUST be on when the WSJTX program is loaded or I get a (WTF!!) error from WSJTX that there is No Soundcard.

? I tried running on 12 volts, same issues.

? Any Ideas??? Thanks!!???? W6TOM

Thank-you DJ!

You guys got me hooked on crochet hooks for the QMX+ !
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73
Karl
KI4ZUQ