QMX+: The easiest and funniest of all the QRP-Labs transceiver kits
TL;DR: if you are unsure about whether you should give a go to building
a QMX+ kit, then just go ahead and get one to build. It is easy, and it
is a lot of fun.
Longer version below.
Yes, you must believe the title: the QMX+ is really the easiest of all
the QRP-Labs transceiver kits. The build is probably second in
difficulty only to the 20W dummy load kit, but that does not count a
transceiver proper, right? HI.
I have built 2 QCX mini, 3 QMX, this QMX+ (no digi stuff here, so no QDX
in my shack, sorry :P), two semi-home-brew versions of the usdx in the
design by Barb WB2CBA, which are kinda in the same family of the QCX, on
top of several other kits from a variety of other suppliers. All these
kits have been a joy to build, including my first QMX Rev.1, serial #
around 100, one of those which had the short in the 5V SMPS, which
required some throrough testing and a little surgery HI. The QMX can
indeed be slightly tricky to build as the PCB is quite packed.
But boy, the QMX+ is on a totally different level of easyness. No
special space constraints. No tight mechanical fits (the postponed
soldering of the two right pins of the tune encoder is really a minor
one, and was solved brilliantly by Hans). No fear of ripping off some
other SMD components while soldering. Well, I have used my 2.5mm scalpel
tip to solder all the QMX kits, without issues, but for the QMX+ you can
easily get on with a 5mm one, no joking.
The only thing that requires some care, really, is the placement of
connectors at the back of the PCB, as the holes in the real panel are
snug and you really need to get the connectors as straigt as possible.
And that's totally straightforward to do, by soldering only one of the
pins of each connector and then making sure that the connector sits
straight before soldering the other ones. But for the rest, there is
really no sticky point at all, and it is much easier to get around it
than in the QMX, where the space is really tight.
The amount of soldering required is not massive by any standard, and
relatively little compared to the QCX mini and the QMX. The stuff to
solder is well spaced-apart. The pervasive use of 0.33mm enameled wire
eliminated almost entirely the potential issues with remaining enamel
and/or imperfect joints. There are literally too few things that can go
wrong during such a build. The worst that can happen is that your cat
jumps on the lab desk splattering all the caps you have just sorted up
all over the place. Don't ask me how I know, OK? HI
I mean, if you can read the assembly manual, and you know which side of
the soldering iron to grab, and you are the average human being who
considers winding toroids as one of the most gratifying and relaxing
past-times on Earth (me! me!), then the QMX+ build is literally a piece
of cake. Almost too easy, and definitely uneventful. It's just amazing
for such a powerful rig.
I completed the build in a few hours, perhaps 5 in total over two days,
without rushing through it. About one third of the time was spent
winding toroids (me! me!). And when I was done with my final checks and
dared applying power, all I got was a fantastic rig, ready to operate
immediately on 12 bands. I spent about 20 minutes in the serial console
after the first boot, checking all the sweeps. They were all almost
exactly as expected. I tinkered with the 20-17-15 LPF for about 10
minutes, trying to squeeze some more power on 20m, but then I realised
that it made totally no sense and stopped straight away. In hindsight, I
should have used that time to make a QSO :)
I have been using the rig for a few days, and it is just great. But
that's another story. This was just to say that building a QMX+ from a
kit is dead easy, and fun.
72/73 de Enzo M0KTZ
DISCLAIMER: This post reflects my own personal opinions, which cannot be
ascribed to anyone else, including in particular any club or association
to which I belong or to which I am connected. I have no vested interest
in any of the QRP-Labs business. I have no business or personal relation
whatsoever with Hans Summers or with QRP-Labs. All the kits I have built
have been paid by me and by noone else, but please don't tell my XYL how
many are they: that's our little secret! I have met Hans once, we had a
very interesting chat and we have exchanged emails on several subjects,
but never on the easyness of building a QMX+ :P My opinion is obviously
biased by the fact that I have a sincere appreciation for the QRP-Labs
stuff that I have built and used so far. I trust you can live with that
;)
--
|
Re: #qmx #ssb CESSB update (Controlled Envelope SSB)
#qmx
#ssb
I've ?read a lot of? numbers but yet grasp the concept how?
five Watt CESSB compares to five Watt SSB from the FT-817 for example
I don't know exactly what FT817 does. But generally speaking:
Envelope peaks of a transmission (PEP: Peak Envelope Power) are much higher than the average. If the PEP is 5W, then perhaps the average power is around 0.5W. If this average-power-relative-to-PEP can be increased, the signal can be made to punch through the noise much better, giving the signal greater range (or ability to handle worse conditions). Audio processing aims to compress the dynamic range, which increases the average power. Too much processing sounds unnatural or even distorted. So it should arguably be used in moderation (like most enjoyable things).?
But no matter what else you do, the actual process of modulation to SSB intrinsically is likely to?produce?RF envelope overshoot. When the RF envelope overshoots it will cause clipping, which causes splatter due to over-driving the power amplifier: RF in adjacent channels which will offend other SSB users off-channel. Normally a manufacturer must want to avoid such an occurrence?so ALC (Automatic Level Control) in the transmitter will reduce the gain to prevent this.?
BUT - another way is CESSB, which is a way of controlling the RF envelope such that the overshoots are eliminated, without increasing distortion. It is found to almost double the average SSB power compared to a very good, well implemented ALC. Perhaps more... I think when combined with speech processing the advantages increase, and it's more like 4dB according to my measurements here.?
This article: "Double your SSB TX power with CESSB"
is good and has links to YouTube videos too, it's a good explanation.?
An explanation centered,? however, around Flex Radio; the conclusion is:
In short, with the FlexRadio 6xxx Signature Series transceiver you are paying for 100 watts but getting the “SSB power” of a close to 200 watts transceiver!?
But that's Flex... $$$$$...?
Compared to a more average transceiver, I think switching on CESSB is like getting the equivalent of 12.5W for your real 5W. And - to re-iterate - all this is only a forthcoming FIRMWARE update to QMX+, and a QMX+? kit including enclosure gives 160-6m coverage and is a mere $150? :-)? ?Even though I do have to say so myself: I LOVE QMX+
|
Re: QMX died pulling out headphones
Headphone socket moved a fraction and something pushed shorted against another component ?? ? Thinking of the PSU board that's above it? . .?
|
Re: #qmx #ssb CESSB update (Controlled Envelope SSB)
#qmx
#ssb
Hans
Again CONGRATULATIONS?
Your tenacity es dudilgense is beyond discription?
?
I've ?read a lot of? numbers but yet grasp the concept how?
five Watt CESSB compares to five Watt SSB from the FT-817 for example
?
tnx
72 73
John
N3AAZ
?
|
QMX died pulling out headphones
I was listening to some CW on 10 meters and accidentally pulled the headphones plug out of the jack a little. Upon pushing it back in, the QMX died and now won't turn back on. What could have caused that?
--
73, Dan - W2DLC
|
Actually, I think I installed the pins upside down. ? Need to remove and flip
|
Photo would help
?
Meanwhile I'm guessing the connectors weren’t level on the board when you soldered them?
|
Re: 50w PA 80m version overheats transformers?
All rather odd.?
Yes the toroids will get warm. ? ?Not sure what temperature you've seen
?
Yes the heatsink will get hot in use . ?It’s not there for art. ?If yours isn’t check your assembly urgently?
?
power input
power output
DC input watts (bias /PTT vs working)
etc please?
|
Re: #qmx #ssb CESSB update (Controlled Envelope SSB)
#qmx
#ssb
?
For those interested, there is a new article on ESSB in the current issue of QEX magazine (September/October 2024) entitled "Class-E SSB tranmission SDR and the Dreaded Arctangent Problem" by James A.R.? Koehler, VE5FP starting on P22.? Link below.? You need to be an ARRL member and log in to read it.
I enjoyed the article from a mathematical perspective. Some interesting ideas; but I also think I disagree with some things in the article, respectfully listed below. Jim VE5FP I don't know if you are a member here but if so this is my feedback.?
The proposition that microprocessors with floating point hardware cost 10's of dollars is certainly not so; STM32F4-series microcontrollers have floating point hardware and cost below $2 in quantity and not much more even 1-off. QDX-and QMX-series transceivers use STM32F446 which like all the F4-series includes floating point hardware.?
The nominal I2C bus speed stated in the article as 1us/bit as nominal is not so; the I2C bus originally was defined with a 100kHz "Standard" speed and 400kHz "Fast" speed. Later speeds were used on some devices at 1MHz and more. The Si5351A specification mentions that it is suitable for 100kHz and 400kHz bus speeds. on QMX I am using 1MHz which experimentally works fine, and also is accepted by the 24M01 1Mb EEPROM chip (even by specification in its datasheet). At 1MHz the maximum '5351 frequency update rate is 16kHz (not 20kHz stated).?
The suggestion that accuracy is very important for the phase accuracy but not for amplitude is in my opinion not correct. Both are important. It seems based on the report in the 2017 QEX article on Polar Explorer that they had phase errors up to 56 degrees. Jim VE5FP then goes on to describe an alternative method to generate required phase and amplitude separately and modulate separately. However. practically speaking, this does NOT solve the phase error problems which remain the same, because you still are amplifying square waves just like the Polar Explorer.?
When you have this kind of phase error - which also exists in QMX, you apply phase pre-distortion to cancel some of it as far as possible. Polar Explorer and QMX both do this. It is the amplifier HARDWARE that inflicts this phase distortion; and the firmware which pre-distorts to cancel it out. However the accuracy with which you can cancel out the pre-distortion makes it questionable whether striving for a high accuracy arc-tangent is relevant.?
In this QEX article the emphasis is on improving the accuracy (and speed) of the arctan approximation calculation because it is most important; Jim states that the squareroot can be more approximated without issue. In all my experiments I have so far found exactly the opposite. In my rather good results so far, I am using the full precision math.h library floating squareroot, but for the arctangent I am using the same very simple arctan approximation used in uSDX which has an error less than +/- 0.3 degrees.?
|
Re: Ultralight vertical offer
Steve, what's the glue you used to fix together plastic, PVC and metal??
?
73, Peter
|
Re: 50w PA 80m version overheats transformers?
Thanks to all that have answered. I have adjusted the bias according?to the instructions, i.e. close to zero bias.? The overheating also happens when driving the amp with 16v. (so far the only other voltage tested) If there were oscillations occurring, wouldn't the output spectrum show signs of this?? I have looked at it with?a spectrum analyzer and it looks good, with odd multiples lower than even multiples. I would guess the same thing would happen if i were only using half the amp (and would expect lower power then) The heatsink nor the IRF510s do not get (noticeably) warm. Nor do the LPF toroids.
|
Re: #QMX PTT for SSB with built-in mic?
#qmx
My first thought (READ speculation) is that you would key up using your straight key/paddle and talk into the built-in mic.
|
Strange/Poor Power Performance QMX+
Hello,
?
I recently bought a QMX+ and had a lot of fun building it and using it so far, but, my biggest problem is the inconsistency of power over the bands. I've tried quite a bit of stuff suggested (re soldering, touching up the joints, verifying continuity, etc.) but I am now out of ideas on what to do. I've attached photos of my RF filter sweeps, SWR sweeps, LPF sweeps, and I/Q sweeps. I am out of ideas on what to do and just want to make sure I am getting the most out the device.
?
Also I am sorry if I am heading in the wrong direction with this, I am new to the hobby.
?
Current RF power:
6m -> 0.9W, 1.43SWR
10m -> 1.8W, 1.22SWR
12m -> 3.0W, 1.18SWR
15m -> 3.3W, 1.12SWR
17m -> 2.3W, 1.15SWR
20m -> 3.1W, 1.10SWR
30m -> 4.4W, 1.07SWR
40m -> 4.1W, 1.04SWR
60m -> 4.4W, 1.05SWR
80m -> 5.4W, 1.05SWR
160m -> 6.0W, 1.04SWR
?
?
|
I am building my QCX+ and am having trouble with the front panel. ?When I plug the panel in, fully seated it seems to tilt back. ?Bottom edge of the front panel and the front edge of the PCB abut one another. ? Is that correct?
|
Re: 50w PA 80m version overheats transformers?
or indeed the way he had routed signals in and out of the amp.? Eg zero coax used.
?
Another thing that has been? seen in these amps? (symptom, overheating )? is single? phasing in the OPT caused by lousy soldering technique.? The amp still produces power but??only through half the magnetics.? The LPF cannot handle this sort of Drive? ?. Bangerter? managed to do this a couple of years back.?
|
There are a few different failures that could cause the measurements you are seeing, including D109.
IC101 should output 3.3-3.6V or so, and you only see 2.17, so either the IC101 circuit is not putting out the correct voltage, or something downstream (including D109) is dragging down the VDD bus.
To further check the IC101 circuit, I would first measure the Vi pin, which should have 11V or so, if not, Q102 could be bad.? Then (if you have appropriate skills/tools) I would lift the Vo pin to separate it from the circuit, and measure its voltage.? If it is less than about 3.3V, IC101 is bad.? We already know D103 is good because you measure an appropriate 0.6V drop across it to VDD.
If all that is good, either D109 or something downstream of it is dragging down VDD.? I guess you should also test Q111: if it is shorted Source-Drain, it could possibly drag VDD down via R114.? When powered off, it should look like a diode in one direction and open in the other, easy to check.? Then the next logical check is D109.? May be easiest to just replace it, but you could also lift one end and measure it to see if it looks shorted or semi-shorted.
|
I just read about this soldering station on another forum, apparently it takes Hakko 900M tips. ?
The handle looks suspiciously identical to the one on my Yihua desoldering station, which also uses Hakko tips......
This might be a better deal: ?
?
73, Don N2VGU
|
Bill,
?
in the QMX+ all the bands (except 160m and 6m) share LPF in pairs (80/60, 40/30) or triples (20/17/15 and 12/11/10). This means that tweaking an LPF to get half a Watt more on a middle band will disturb the output PWR on the other bands that share the same LPF.
?
I personally playeth the "squeeze-me-and-stretch-me" game for about 10 minutes, saw that it was not worth the effort, and started calling CQ straight away HI. Got an immediate 599 and 20min rag-chew on 20m, which is the band I had tried to squeeze and stretch the longest,? and which is still the one with the lowest PWR of all (2.7-2.8W).
?
Most operators fall off their chair when you tell them you are running 3W (I don't even bother saying 2.8W on air...), and if condx are good they rush off to confirm "UR RST IS 599 REAL 599 REAL" in the following QTC? :)
?
Enjoy using your QMX+. It's a fantastic little rig ;)
?
72/73 de Enzo M0KTZ
|
Re: 50w PA 80m version overheats transformers?
Hi Jonas,
?
“T1 becomes hot” makes me wonder whether you could be experiencing oscillation caused by RF feedback through bias or QSK circuitry. Does your power meter move in accordance with your keying?
?
I recommend you change supply voltage between, say, 12V and 20V at small increment, and see whether the problem exists to some extent (not very hot, but still warm) at lower voltages, or appears suddenly above a certain voltage (such as 18V). If the latter, I would suspect oscillation is likely. The culpit would be degradation of RFCs L9 and/or L10.
?
73, Aki, JO4MTH
|
On Sun, Oct 6, 2024, at 19:36, Donald S Brant Jr wrote:
I use and recommend to use this Knipex tool and avoid the hassle: ?
They sell additional sizes of blades but I have had great success with the default one.??
You may have just saved what I jokingly call my sanity! One of the things I was not looking forward to when I take up my second attempt at building the QMX+ was the enamel stripping shenanigans!
Michael WD0OM
|
Bruce Akhurst
Daniel Conklin
Peter HB9EBE
Timothy Fidler
Donald S Brant Jr