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

开云体育

? 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+ !
--
73
Karl
KI4ZUQ

May not be your problem, but I ran into the same issue. Powered via the QMX+.

On Sun, Jul 7, 2024 at 08:25 PM, Larry Christensen wrote:

I’ll try the cookie sheet then an other antenna.??

Actually the 4 inch steel octagon cover of an electrical box is almost the perfect size for a GPS ground plane and works well for me.
73, Don N2VGU

Now that I think of it, check the ground and power supply connections on the top of the GPS board and see if you can confirm solid connections.

73, Gregg

Hi Larry,

FWIW, mine is not on a cookie sheet, but in a window sill. But I know the cookie sheet helps a lot. Technically, they do much better on a cookie sheet.

Hopefully, you get it working.

73,’骋谤别驳驳

Hi Larry,

make sure your GPS jumper is not shorted to the GPS SMD connector. You can see it looking at the side of the board. Mine works fine, but I am jumpered to VDD. Your jumper needs to be very flat to not accidentally short to the SMD connector. As far as I know, those GPS antennas are all similar, so feel free to try another. Stick it on a cookie sheet if you want better performance.

Good Luck,
‘Gregg W7GRM

I can’t get my QMX+ to connect to the gps. I have the setting for QMX-internal. The jumper is set option 2 for the battery. The clock is on. Real time clock set to QMX+ RTC
Hardware test for GPS view shows “ No Data”
I’ve let it run for well over a hour several times

I’ve removed and inspected all the gps connections all look good.?

I’ve also tried a factory reset still no connection.?

Is the gps antenna the same on the clock and U3S units, I have three other QRP Labs GPS on those. If they are the same I could test the antenna. ?

Thank you
Larry NA0F

?

?

/g/QRPLabs/files/Alternate-QMXPlus-Front-Panel-Assembly.pdf

Could someone point me to the thread describing the alternate method of soldering the display? ?I think it required a partial disassembly of the board, but allowed easier soldering?
Thanks in advance.?

Well, what the hell!! ?I knew it would be something really stupid that I did...or didn't do. ?Of course, the jumper fixed the receiver. ?Hot dog!! ?Thank you!! ?I saw the trace just end, but with so many layers, I just assumed it went underground.

Happy dance....well, as dancy as a 71 year old guy who loves cookies can dance.

The transmitter isn't keying on CW, but that may be easier to track down now.

Whew!!!

Good to hear! ?Mine is on its way to him tomorrow. ?- Dave, AI7R

Does your Z-match tuner have a switch for a resistive bridge? If it does, then you need to use it when tuning. If no resistive bridge or if you don't use it, you will always trigger the protective SWR in the QMX. If no resistive bridge, then you should tune the antenna system with a NanoVNA or other antenna analyser before transmitting with the QMX.?
--
73, Dan? NM3A