I'm having a blast with this thing. I've not done much else this week other than operate on 20m with the QDX I finished on Monday. Built as a low band 12V, I started running at 8V and worked my way up to 12 basically a volt at a time checking the RF power and current draw. Power output seems a bit more than I expected based on the manuals and I seem to be getting out well even with a compromised antenna. Here are some numbers with the QRP Labs dummy load.

Final update:

I received my parts and removed the AOD403 without further incident. That was so easy I decided to go ahead and plop in the new one. I ended up not being satisfied with how it landed and, in trying to remove it to have another go, I ended up lifting the OTHER leg's pad.?

At this point I decided I may be operating a little too far out of my own current skill-level. So I contacted Jeff Moore and shipped the whole thing off.

Jeff found some suspect solder joints, a distorted (by installation heat) power connector, and added the 1N4148 suggested for my 2023 Rev 2 board. He was able to build back up both solder pads for the AOD403, which is now functioning beautifully. In doing diagnostics he noticed some high and flaky SWR readings and spent a few days head-scratching and replacing a few more parts. A lot of labor on a $100 radio!

But last night I was on the air and, despite challenging band conditions, made a QSO with a friend half-way across the country on my simple wire dipole. We gave each other similar signal reports; him running 75 watts and me, well, on the QMX at 12v.??

Thanks to John for your diagnostic help and encouragement. Thank you Jeff for doing top-notch work and providing an accessible backstop when I finally acknowledged I was out of my tinkering league!?

Two other notes:

Using my device for CW practice, in practice mode, with a QRP-Labs dummy load, it had a terrible thump that made it mostly unusable for that purpose. On the air with a real antenna that thump completely disappeared and it is extremely well-behaved. Ironically, Hans pushed out several firmware improvements while I was without my unit, and v.16 -- with the fixed CW algorithms, was released the day I got it back.

And today comes yet more new firmware with AGC. Wow. I feel like Hans has really cornered the market on a usable, portable, affordable, and uniquely feature-ful QRP transceiver. Brilliant!?

I spotted a really trivial bug in the GPS display from terminal on the QMX in version 1_00_016 of the firmware

The month is a month out - took the following snap on 17th Feb, not Jan. ?The UT Date is out by a month. ?Really not an issue but mentioned in case the code is used elsewhere.

73

Paul
M1CNK

开云体育

On Sat, Feb 17, 2024 at 01:13 AM, Paul Christensen wrote:

See below.? The high "Smooth Samples" setting seems to eliminate much of the audio clicks.? The remaining settings give reasonably good dynamic range while limiting strong signals. I'm still experimenting with values but this is a good start.

Paul, W9AC

I have just tried this and smoothing makes no difference to the clicking for me.? It seems much more related to the AF gain with the clicking being very much reduced with the AF gain turned down and seems to be related to the clunking that is sometimes present when keying on older firmware versions.? With S9=S9 the clunking is very pronounced and makes keying barely possible.? With S9=S0 then this is reduced to the spark like sound and with the AF gain dialled down becomes perfectly manageable but present.? However I have not tried it on air to see if the incoming signal will be loud enough to hear.

Which power supply did you use during the last switch off from normal work?

I meant of course "uncommon scenario":
"...I think my use case to provide power to the QMX from one power supply and have a laptop conencted with a different power supply with at least one power supply ungrounded is not an uncommon scenario, if you run FT8."
--
73, DB2OO -Joerg

Thanks, Hans, this update (AGC) really makes a huge difference! ?As a feature request, could the S meter have a peak hold function? ?

I'm not sure if this is new to 1.00_017 but when selecting a preset (as per 4.9 in the manual), the preset number is not displayed and the display format is not as per the documentation. ? I prefer how the current display shows the preset frequency directly below the VFO frequency but would like to see the preset number too, maybe to the left of the L?

Even if it is not yet Easter my QMX stood up from the deaths yesterday:

Based on Hans' feedback to my dead QMX as was pretty sure, that the CPU would have been killed due to a voltage difference between

• the USB connection to my laptop (running on one potentially ungrounded power supply)?
• the 12V supply power comming from an ungrounded lab power supply

Yesterday I disassembled my QMX from the enclosure and pulled out both power supply (SMPS) PCBs.
I then added jumper wires for GROUND and VDD (3.3V) to the main board PCB#2 connector and supplied 3.3V (JP104 Pin 4 and Pin 2 GND) from a current limited lab power supply and slowly increased the voltage while watching the current.
At 3.3V I saw a current consumption of approx. 150mA --> Hooray, CPU not shorted, most probably OK!
I then checked the PWM_3V3 and PWM_5V signals on the main board, that are directly coming from the CPU --> 116.4kHz rectangle signals --> CPU is working.

As a next step I put in the SMPS PCB#1, to create the 5V and pass through the 12V, that I connected through the power supply connector with 3.3V still being supplied directly to the main board.
Again I had high current consumption on 12V --> problem must be on SMPS PCB#1!

I pulled out SMPS PCB#1 and put in SMPS PCB#2 for 3V3 supply. I fed 12V to the main board 12V connector of PCB#1 (JP101 pin 4) and saw 3.3V coming out of SMPS PCB#2 and a nice 116.4kHz signal on PWM_3V3:


I was now suspecting, that the 5.6V Z-diode D108 on SMPS PCB#1 had a short, desoldered it and soldered in a new one.
Unfortunately a 3W 5.6V Z-Diode, that I had ordered, was too big to fit into this place, so that I had to put in a glass 5.6V Z-diode.

Put in PCB#1, connected 12V to the power connector of the PCB, slowly raised to voltage and again hooray, QMX was working again!!

I updated to the firmware from 1_00_012 to 1_00_017 without any problems and the QMX seems to be working fine.

That D108 obviously took up its protection role and died with a short is for me a strong indication, that the SW based switching regulator still has problems...
I think my use case to provide power to the QMX from one power supply and have a laptop conencted with a different power supply with at least one ungrounded is not an common scenario, if you run FT8.
--

Vy 73, DB2OO -Joerg

On 17/02/2024 08:13, dl3naa via groups.io wrote:

Karl, there is another possibility

Which reminds me, it is possible to bypass the QCX filter with a switch.
Makes SSB receive possible but not good. WSPR does its own filtering.

73 Alan G4ZFQ

On Wed, Oct 11, 2023 at 07:07 AM, Hans Summers wrote:

So the manual is correct... according to experience - experience being slightly different from simulation expectations - and if you build according to the manual you probably stand the best chance of getting a good output power.?

Hans,

Forgive the resurrection of this thread, but, in beginning to sift through the parts of my QDX kit, I noted the cores designated for L2, L3, L4, L6, L8, and L10 were described as "37-10 toroid (shiny black)", yet those supplied to me were a garish blue and yellow color. I am a UCLA graduate and these are my alma mater's colors and that's fine. I am nonetheless leery of these not being "shiny black".

Is my kit-building experience over as I know it or is there hope for me yet?

** sobs mournfully**

TIA.
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."

Karl, there is another possibility but I never tried it myself as I am a huge CW-fan and dont want to loose the filter:
With this Modifikation you should be able to use a QCX for transmitting AND receiving WSPR.

Good luck!
Peter DL3NAA

I've listened to this weekend contest in 20 and 40m bands and tinkered with AGC settings some more. I've also tried Paul (W9AC) suggestion to increase "Smooth samples", and it seems to alleviate the clicks on TX.
My goal was to keep reasonable good dynamics and make RX as less tiresome as possible. Here's what worked for me:



It's nice to have so many options =) =)

Regards,
YO3GFH
op. Adrian