I am entering a dangerous area … my wife paid for the QCX mini as a late Christmas present … and lately she asks me: And the transceiver? 
6 Likes
QCX Mini construction complete and tested!
Managed a quick activation on Wednesday of Broomy Law GM/SS-209 and to introduce my QCX (30m) mini to the world of SOTA .
Only a short activation during a 30 minute break from work , managed to work 13 chasers with several being S2S best lunch break I have had in while.
73
Graeme
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My 40m QCX mini got its first outing today. I had a few issues with the build, mainly due to my own clumsiness. First, I tombstoned one of the SMD RF chokes and when I grabbed it with the tweezers to stick it back down again it slipped and flew across the room, unable to be found, so had to order some more in 0805 size (I ordered 10 because true to form, I managed to do the same to replacement 1). Then I managed to drop the BNC connector on the ground and the plastic inner separated, so I ended up with an SMA connector I did have handy, and then while I was troubleshooting low receive audio (incorrectly soldered L4) I fried Q6 complete with cracked case and magic smoke release. They took a week or so to arrive, but finally got it up and running earlier this week.
Contacts were made into VK2/4/5 with about 2-3 watts (my power meter didn’t survive a work trip… 
)
11 Likes
Thanks for the update.
I begun last week and completed all the uSDX SSB mod stages. Hand soldering the 0603 parts was interesting but it worked fine. All test measurment are perfectly on spot.
Now it’s up to build the actual kit.
73
Joe
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And it’s alive 
Now i need some tuning of the torroids to get max power and check for IQ and BPF tuning. This is done totally different in uSDX than the original.
Currently about 2,5Watt on CW maximum.
73 Joe
6 Likes
My completed QCX mini (40m) was shipped today. I ordered it on 12.21.20! I knew it was going to be a wait and kinda forgot about it.
My MTR4bv2 was also shipped today! Ordered that 2 weeks ago tomorrow. Crazy coincidence.
Coupled with my Venus SW3b I’ll have quite a quiver of QRP transceivers! What a cool time to be getting into CW mode.
Now, I’d love Hans to build a 2m/6m mini I’d take 2!
Erik
KE8OKM
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Great! I ordered the 17m one on 31/12 so maybe soon?
If you have the SW-3B (Nice toy!) why did you order the QCX 40m band?
I find these transceivers fascinating! It will be interesting to compare their performance in similar conditions (antenna, same time of day and location)
I am also ordering a 17m QCX mini kit and it will be great to have a fully assembled unit as a reference.
Erik
KE8OKM
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I built the 17m from one of the first shipments back in Dec. Awesome rig. I set my mi/W record with it.
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Received my QCX-mini today. Powered up perfectly with my 12.0v Bioenno hopefully this evening I can get it to RBN! Also found the red one in the mailbox. What are the chances!
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I am struggling to get more then 2,5 Watts from my QCX mini. I know the video that explains the tuning but before I start to remove windings from the torroids just a quick community check:
For the 20m band version: Did you need to change the number of windings on the torroids?
If yes, to which number of windings?
Maybe share a picture of the pcb? Only 20m makes sense to compare.
Thanks a lot
I had the same problem with my QCX Mini for 30m.
Then someone recommended this video to me.
Now I have 4,5 Watts
73 Armin
Hi Armin,
Thanks for link. I know the video and did adjustments to the spread of all 4 torroids. But I have not started to remove windings. Only spread them out or moved the closer. But there is almost no change in doing so (0,2 Vp-p).
Might still be another issue as I did the SSB uSDX modification. So it is only partially a QCX mini anymore.
But I might try removing windings on L3 as everything else did not bring much improvement.
73 Joe
Hi Joe
With my 30m QCX Mini I had 3 Watts … and removed 2 windings one by one from L3 … I would give it a try on 20m as well.
73 Armin
I removed 2 windings from L3 and and found a bit of improvement at L2. Not much but almost at 3 Watt. And I found a suitable electret mic and gave it a quick test and received on my 817nd. Not HIFI audio but pretty good for the small rig and a 20 MHz Atmel Chip that does the SDR DSP.
Will see if the groups.io community has more ideas.
Enough for today
73 Joe
Other people have said that they got much more power out of it. Up to 6 watts.
I have now stopped looking for a few 100mW. The chance of breaking something is high.
The higher the frequency, the lower the transmission power will be… and 3 to 4 watts at 13V is ok.
It also depends on the operating voltage. Here the bandwidth is quite high.
73 Armin
2 Likes
Hello Joe,
I was facing the same situation when I built my 20m QCX-mini back in January. After initial power-on, output power was only about 2 watts at the dummy load.
IIRC, I had to remove 2 turns from L3 to get a bit more power. I followed the instructions Hans gives in his video about adjusting L2 and L1 for max. output power. Eventually it turned out that for the 20m version it is possible to miss the optimum (i.e. max. output power) if you spread the turns over the whole circumference of the toroid or squeeze them as much as possible (i.e. if you use the extreme positions only).
The adjustment needs to do be done in small, alternating steps between all three inductors. I believe I spent hours doing so. I also found that changing the frequency, say 14.000 MHz -> 14.100 MHz -> 14.200 Mhz -> 14.300 MHz will show a significant variation in output power. It also helps watching the current consumption. You might even find frequency/ voltage combinations where the QCX-mini draws a lot of current but delivers only little output power. An effect I did not fully understand.
From memory I would say that removing turns from inductors other than L3 is not necessary. But carefully tuning is mandatory on 20 metres.
After a lot of tuning I ended up with about 4 watts @ 14.0MHz and 5 watts @ 14.3MHz at a supply voltage of 12.5 V.
Good luck and 73,
Roman
1 Like
Hi Roman,
Thanks for the great guideline. I will give variations in frequency a try. And again spend time with adjusting L1 and L2.
A pitty that that 20m as the most used SOTA band is apparently more tricky then other band versions. But anyhow great what the little rig can do.
Just looking at the current consumption and my joice of a 4S 1350 mAh LiFePO4 was okay for a multihour activation
73 Joe
… I believe that’s because slight changes in inductance (such as squeezing or stretching turns) has a much larger effect on the higher bands than on the lower bands where one turn more or less won’t have much impact. I didn’t build a QCX-mini for 17 metres but can well imagine that tuning is tricky, too. Tuning my 60 metres QCX-mini was almost “plug and play” after I had finished the 20 metres version.
It is a marvellous rig and I won’t complain that it took some effort to complete it. I learned a lot about class E amplifiers while tuning 
73, Roman
1 Like
Hi,
I build my QCX Mini 20 v2 board two weeks ago (finally) and straight away I wound L3=15turns so one less then manual indicates. I also ensured that all windings on L1, L2 and L4 are evenly spaced arround entire core. T1 is on another hand has each section as tight as possiblegiving 2-3mm spaces between each section.Without any additional tuning I got 4.5W @12V and close to 6W @ 13.8V. I will check current draw later on this evening, I never though to check that.
I have another QCX Mini 40 but rev.1 which I started to convert into uSDX, very interested to see how this will go. I have opted out for version without T1
73, Marek