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Your QMX output experiences @12volts...?..and by the way, what an amazing radio.

 

So, having had a few hours to play around with this great little rig, I am wondering what most folks are seeing for output. I am running the 60-15m version and see no less than 3 watts or better across all the bands. I think that is pretty good. I could likely get it to 5 watts easily but it would mean 12.5 to 12.7 volts. I normally run resonate, purpose built antennas, but still, those little mosfets can only take so much, and what's a few hundred milliwatts between friends?? :).
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So, interested to hear what others are running (pwr/voltage) and what your experience is.
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As an aside, I was surprised to see the LSB/USB option and being able to open the rig up beyond the 300 hz filter. It sounds really, really good on SSB.
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Hats off to Hans for his incredible work. My faith in soldering has also been restored :)
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Scott
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??? Using my QMX+ as a WSPR Beacon, this was built by QRP Labs for me and is a 12 volt but I use a 9 volt DC to DC converter and get about 2.5 watts out. I do this to give some added protection to the finals and because I use a solar panel charged battery bank that can have as high as 14.4 volts.

??????????????????????????????????? W6TOM

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On 2025-01-10 19:40, Scott VY1CO via groups.io wrote:

So, having had a few hours to play around with this great little rig, I am wondering what most folks are seeing for output. I am running the 60-15m version and see no less than 3 watts or better across all the bands. I think that is pretty good. I could likely get it to 5 watts easily but it would mean 12.5 to 12.7 volts. I normally run resonate, purpose built antennas, but still, those little mosfets can only take so much, and what's a few hundred milliwatts between friends?? :).
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So, interested to hear what others are running (pwr/voltage) and what your experience is.
?
As an aside, I was surprised to see the LSB/USB option and being able to open the rig up beyond the 300 hz filter. It sounds really, really good on SSB.
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Hats off to Hans for his incredible work. My faith in soldering has also been restored :)
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Scott
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I don't recommend running it over 12V to get more power.? I believe Hans when he says that you significant increase risk of damage to finals, etc.? Morse code only may be a bit more forgiving due to its low duty cycle, but FT8 and other digital modes have long carrier-on times that are already stressful.?
You can likely achieve a bit more power if you really want by internal tuning adjustments to the LPFs for your lowest power bands - but I wouldn't bother.? The difference between 3W and 5W is less than 1/2 an s-unit at the receiving station, which most won't even notice.? ?One of my first QMX contacts was to New Zealand from Utah with 3.2 watts.? You will have more impact on your signal strength by making sure your antenna is efficient.?
 

Great, SSB working now !!
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Has there been an "official" announcement ?
 

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QMX has always been able to receive SSB. SSB transmission is still in the future, I think!

Paul -- AI7JR

On 1/10/25 21:29, Gert van Kruiningen via groups.io wrote:
Great, SSB working now !!
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Has there been an "official" announcement ?
-- 
Paul -- AI7JR
 

Scott VY1CO via groups.io <scott.vy1co@...> wrote:

So, interested to hear what others are running (pwr/voltage) and what your experience is.
12 V, it's a little above 4 W at 20 m (I didn't test on other bands).
Difference between 4 W and 5 W is so small (in terms of S values) that I
didn't bother stressing the finals.

I had to replace finals in my QDX several times (they never failed in my
QMX), so I want to keep some safety margin.
 

Indeed. Thanks Adam...agree with you and Stan. I am pretty lucky, for once in my ham career, to have some room. have mono band yagis for for the bands of interest so a few Mw one way or the other is not much...that said, when you are only running 3 watts, an increase to 4.5 watts can make a difference.? Regardless, just please to have this thing sorted. I can not believe how much is packed into this...when I ran the diagnostic software on putty I was blown away.?
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I think next step for Hans, when he gets a minute to breath should be a multiband Amp...In fact I am wondering if I can make something of my QLabs 50w amp and a series of relays to switch out the low pass filters...
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73
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Scott
 

On Sat, Jan 11, 2025 at 04:47 PM, Scott VY1CO wrote:
I am wondering if I can make something of my QLabs 50w amp and a series of relays to switch out the low pass filters...
There have been lots of posts on this group about using the 50w amp with QMX.? It would be good to read them before going far on that path.
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I'm not going to bother with that.? The QMX is supposed to be QRP, and for highly-portable use.? I have a fine 100W transceiver if I want more power at home.
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Stan KC7XE
 

I have QMX 60-15 running at 11.5-12.3V. At 12.0V I get from 5.2W to 4.7W with lower the frequency higher the power.
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I run it stand alone and sometimes with MX-P50M (45W PA), mostly chasing SOTA? & POTA activations as well doing odd POTA on FT8 myself.
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This is a great rig as all other rigs Hans has produced. My only gripe with QMX is, that it is a very fragile electrically. I burn twice mine already. First time I pulled power cable while TRX was still on. Second time I connected PA when it was already on and QMX was off. In both cases power supplies had to be mended.
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I would say this is the only weak spot I am aware off. It supposed to be portable rig but requires treatment like fragile lab gear.
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---------------------------------
73 de Marek SP9TKW
 

Two things I've done here is build a QMX+ because it has multi=band capability
and go to a 17 foot whip. The power output is no problem these days as
the solar flux is high. You don't need an amp, but using a cell phone if in range,
to post your station, is a way to get a lot more activity. A smaller resonate whip,
or a light weight tuner like the Elecraft or 4 State is more effective than an amp.?
I don't think the QMX+ is fragile, but the QMX is too tiny for me on a practical level.
Let's just say I burned up a few HiHi.?
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I think when Hans gets the time an auto tuner in the development
board space would be my wish. Then 1 watt would be adequate most days.
It is QRPLabs after all.??
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Really? I did know this.? I have never heard any yet.? Then again, I have heard very little CW, as I have not yet spent hours scanning up and down the bands on my new prebuilt QMX as it is a bit tedious.? I did tune into our local clubs "VRC slow code net" practice session on 10M so I know the unit is working.? ?Obviously, I need to spend more time scanning to hear some action.
 

Hi,
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I am putting in right here with my enquirer about QMX being hypersensitive to supply voltages over 12.00000000000000. That QMX does things I would like to.. except for frying finals so easily. I have exposed my QCXs (remember those?) and another QRP rig with the same finals to battery voltages up to almost 14 volts with no ill effect. That other radio has been here long enough to accidental operation with no antenna connected!!
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I would to know why the QMX behaves this way. I would like to know how these have been powered..AC power supplies or isolated batteries that are not connected in any way to the power grid like a float battery charger. I wonder if the duty cycle has pushed the failed radios over the edge to destruction. I have only operated CW at full power and digital modes at dramatically lower power. No failures.
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On some radioes there is a "Drive" control right on the front panel because it is *important*. transmitters that include SSB control the power level with the mic level control..also located on the front panel for the same reason.
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Any replies I get my questions will be used to help me evaluate the belief that "12 volt" ?radios are and should be so very fragile. That investigation will be part of a wider investigation that includes addition of that drive control to radios that are without them.?
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Thanks in advance for any information about this question..or these questions.
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73,
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Bill ?KU8H
 

I do not believe QMX finals are nearly as fragile as they are reputed to be.? I have not blown any in my QMX+ nor the two QMXs that I own.? And if you are only operating CW, 12.0V is a good guideline, but operating a few tenths or more above that will likely not ever cause problems, if you operate into a reasonably well-matched antenna system (which I postulate is a 2:1 SWR or less).
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But QMX is designed for data modes and beaconing also.? And if you operate above 12.0V with FT8 or long RTTY bulletins or a WSPR beacon, you are creating significantly more risk of failure, especially on a hot day or if the wind is blowing your wire antenna and fluctuating the SWR.
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According to messages I have read here in this group, there are indeed a few things that are known to damage the QMX/QMX+ finals, one of which is transmitting full power into a high SWR for more than just a few milliseconds.? The internal SWR protection firmware tries to prevent this, unless you disable it.? But if you use a switched-relay antenna tuner at full power, there can be many very short 'spikes' of high SWR as the relays switch (depending on the type of SWR bridge the tuner is using).? And while these short spikes may not immediately kill the finals, they may cause some damage which will lead to failure - a few posters have reported such failures.? And such failures are much more likely to happen if your supply voltage is over 12V.
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And yes, if QMX had an output drive/power control, you could eliminate most of the risk of failure in the finals by turning down the drive.? I hope such a feature will be added to the firmware.?
 

I understand qmx is more complex than the qcx, and ability to do ft8 wspr etc can stress the transmitter and possibly also the dc/DC. I would be interested in operating wspr on 160 and 80 meters, where a few watts may be more beneficial. Here I sense need to drop supply a little below 12 volts, and I see a boat anchor bench supply across the room that can do that.?
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I did fire up the U3S on wspr, it's stock output is adequate still on the upper bands. Only one final is at risk here.?
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As for QRO when the QMX can do SSB, even a 20 watt PA might be an asset.?
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Let's patiently see what emerges.?
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Curt
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Thank you for your input Stan,
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I looked at the info in QRPLabs web site and I see that the QMX series have the same final transistors as my QCXs and the PFR-3. My experience is those are robust parts. In have not looked to who is running classic, D, or E. That might make a difference but it clearly states those transistors in the QMX do not even need a hearsink.
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It is possible to destroy some pretty rugged vacuum tubes leaning on them too hard. some of the same cautions apply. Meanwhile My ham hobby has been morphing into the 21st century. My sealed lead-acid 12 volt batteries get up a bit over 13 volts at full charge and the new LiFePO4 batteries get closer to 14 volts with the present charger. I have all of my "12 volt" stuff using the Anderson Power Poles and all the 5 volt stuff using USB cables & connectors. I have two different kinds of power sources and I would like to not clutter the local environment or picnic table with several more. It would be trivial to acquire an 11 volt supply, a 9 volt supply, and on and on then inventory several different connector types to avoid disasters. Too much stuff to carry to the park or to Field Day. Also clutters the desktop.
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So now I have mentioned some of my reasons for asking my questions. If I get more responses like the two I have now I will move the QMX up on my list. I do not require every last milliwatt so all I need is the means to reduce power for rtty and other high duty cycle modes. Meanwhile..I can operate one of those on CW as it comes off the bench. I started with two watts on CW and SSB and worked a lot of QSOS with modest antennas.All those bands in one small box!
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73,
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Bill ?KU8H
 

A relatively easy way to deal with the QMX power in your situation is to get one of the inexpensive buck-boost power modules (the 3amp ones are very small), set its output for 12V (or your desired setting), and build it into your powerpole to QMX cable adapter.? ?These work quite well for qrp voltage regulation, and work with your supply voltages.
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That’s what the “tune” menu does. With a selectable percentage. ? When I use a match with my qmx it’s a BLT + that I built which has a dummy load in line with the antenna, so that cuts the mismatch down to 2:1 max. Then, I go into the tune menu at the frequency I’d like to operate and it puts out 25% power into the tuner/antenna. I fiddle for the dip and we’re off! ?I’ve not had any final issues with any of my qrplabs kits. But I believe the function you’re looking for already exists unless I don’t understand the ask, which my wife will tell you is a possibility ?.?
 

Scott VY1CO via groups.io <scott.vy1co@...> wrote:

In fact I am wondering if I can make something of my QLabs 50w amp and a
series of relays to switch out the low pass filters...
Definitely. I'd use LPF selector signals from QMX to switch bands.
 

Stan Dye via groups.io <standye@...> wrote:

I'm not going to bother with that.? The QMX is supposed to be QRP, and
for highly-portable use.? I have a fine 100W transceiver if I want more
power at home.
The problem, as always, is money vs time.

For a long time I didn't want to spend money on a proper, factory-made,
100 W transceiver, especially as I'm mostly interested in CW, so a
transceiver doing SSB would be an overkill.

I'm still weighing pros and cons (DIY vs something that just works, plug
and play, and is on warranty in case it doesn't).

On the other hand, QMX isn't too complicated for me to diagnose and fix.
It's a simple and elegant circuit. A factory-made rig, once warranty runs
out, probably would be.

My concern is with the receiver. How does the QMX receiver compare to the
one in, say, Yaesu FT-891 (a rig I want to buy)?
 

Stan Dye via groups.io <standye@...> wrote:

I do not believe QMX finals are nearly as fragile as they are reputed to
be.? I have not blown any in my QMX+ nor the two QMXs that I own.? And
if you are only operating CW, 12.0V is a good guideline, but operating a
few tenths or more above that will likely not ever cause problems, if
you operate into a reasonably well-matched antenna system (which I
postulate is a 2:1 SWR or less).
I blown finals in my QDX by driving a poorly matched load (including when
the BNC connector made a poor contact). QMX has a protection against large
SWR.

And yes, if QMX had an output drive/power control, you could eliminate
most of the risk of failure in the finals by turning down the drive.? I
hope such a feature will be added to the firmware.
There's hardware for that, so it should be easy to do in firmware...

On the other hand, you can just lower the supply voltage.

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