Armin, I can imagine your shock, because you didn’t always have luck with the QMX.
I find the menu item where you can test the SWR at 50% power (without worrying about the power amplifier) very reassuring.
73 Chris
73 Chris
4 Likes
I’m currently working on a special version of the QMX with all include in the housing.
- Lipo battery
- 1W audio amplifier with speaker
- Touch paddle on the housing
- “Fuchs” resonance circuit that tunes 10m wire at 30,20,17 and 15m
- Antenna wire is turns around the housing (BushAnt©
) - Size 15x8x2.5cm
- Weight 300g
73 Chris
The pictures with a QCX don’t show everything yet, still in developping
10 Likes
Nice! You should call it the QMX-XL (Xtra Large) 
How about an internal battery charger for the LiPo?
1 Like
Nice idea! And here should still be room for the balancer board, although it is starting to get tight.
73 Chris
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I just received my 60-15m assembled QMX yesterday and am delighted with it.
Got on the air at my home QTH and had some fun, when paired with my 40(15)/20m linked dipole it will be a great SOTA rig. I ran it directly off my PowerFilm integrated solar panel and powerbank, but also have a 3S LiIon pack for lightweight ops. I also found a 700mAH 3S Lipo which is not suitable for flight use anymore, but will be great for a quick opportunist activation.
Will look at the antenna shown in this thread, it looks quite compelling…
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Hi Chris,
Working on the same concept, QCX 20/30, all in, Fuchs, LiPo, VK3IL paddle, bush antenna copy @DL1CR… How do you fix the QMX in the housing since you can’t use the rails?
Hi Peter
nice to hear that you had the same idea. I was very inspired by the KH1 from Elecraft. But the telescopic antenna on a radio is too cumbersome for me.
The QMX is held in place by the holes for the 3.5mm jack sockets and held in place by a screw at the top right near the speaker (missing in the picture). There are same part for screws in housing, that fortunately fit.
In addition, I will glue foam rubber into the cover, which will hold the board on non-critical RF locations. Likewise shielding if necessary. The circuit diagram will come in the next few days.
How goes your project?
73 Chris
8 Likes
Hi Chris,
Still designing and finding out how I want it. Here is my QMX interim solution. The final one will be based on QCX and much smaller (I hope). And obviously in one box all included…
73 Peter
3 Likes
My new not finish yet, QMX/QCX/ Hand style universal Adaptor- 2x18650 DC/DC converter for 12 V, audio amp, wip tuner if you have several QMX, just replace for a few seconds.
1 Like
I originally built an 80-20m QMX. However, I use the 60 - 15m QMX for most of my activations now. 80m would certainly be useful for an overnight SOTA expedition, but I never really do those kinds of activations anymore; and I have the KX2 in case I change my mind. I’m finding a trapped EFHW is a very light and convenient partner for the QMX. Whilst I have a 40/30/20 at the moment, I will make a 30/20/15 version as soon as my new Pico Traps arrive, and then also a 60/30/15 version. I was originally put off the 49:1 EFHW by rather large inefficiencies on lower bands. However, with the right ferrite material and the right winding technique, I can honestly say I’m not noticing any difference at all in my signal reports.
30m of wire is about as much as I like to put up on a summit. When using 80m, I found proximity to the ground had a big effect on SWR, so I had to take my 10m mast with me, completely negating any weight savings gained by using the QMX.
73 de OE6FEG
Matt
1 Like
Matt,
I can’t remember in what context the VNA loss graphs of various EFHW transformers, measured back to back, were uploaded for comparison.
In any case, this is NOT to be understood as a recommendation to carry out reflection and loss measurements back to back, because this is too imprecise/unspecific and therefore only suitable for seeing the order of magnitude (without having to do any calculations, hi).
BTW, Back to back configurations make sense for load measurements (e.g. for thermal measurements).
73 gl, Heinz
And because it’s Sunday, something for dessert … have fun.
EFHW compensation, or those little blue capacitors
3 Likes
I own two QMX, high and low bands. Now I’m using them as handheld, "“KH1"” kind of setup, and I’m very happy. On my last activation I managed several S2S on 30m and it was a nice fun experience.
The worst part is fine tuning the antenna/counterpoise and not having the SWR protection to shutdown TX from time to time (having to reboot the qmx).
EA3/TA-003
EA3/TA-017
BTW, I attach the counterpoise using the GND of a mini-jack connected to the (otherwise unused) PTT port.
5 Likes
I’m trying to decide between the 9v and the 12v. It seems most users are going with the 12v and I am leaning that way simply for the convivence of being able to use my existing batteries. However, looking at the build manual it states that the 9v version outputs 5w whilst the 12v version is max of 4w. That seems rather significant and has me on the fence.
It’s always nice to get max out, but in practice the difference between 4W and 5W will be undetectable at the receiving station…
2 Likes
My QMX at 12v gives a minimum of 4W and a maximum of 6.5W depending on the band.
73 de OE6FEG
Matt
“The worst part is fine tuning the antenna/counterpoise and not having the SWR protection to shutdown TX from time to time (having to reboot the qmx).”
No need to reboot. Just enter the menu and exit.
73, Zrinko, 9A7AM
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I don’t think there’s any real difference in power output between the supply voltages. I can’t see a reason why somebody would choose a 9v build over a 12v build. A 3S lipo is such a convenient power source.
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By the way… the only difference between the 12V and the 9V version is in the winding of the output transformer - one turn more or less. Can be easily changed if you built the QMX yourself.
I use the 9V version for my QMX carrot so that it is as small as possible.
73 Chris
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4w with 12v verses 5w with 9v according to the assembly manual.
The chart below shows the measured power output vs supply voltage for the standard 3:3 winding (Red line); at 12 V supply the output power of around 8 W is too high and likely to cause overheating or failure of the power amplifier transistors. If you wish to use a supply of 12 V the 3:2 winding style is more suitable and will produce 4 – 5 W output for 12V supply. The graph shows 40m but other bands are very similar.
1 Like