Have you tried 12.0V? -Chuck Harris, WA3UQV On Tue, 14 Jan 2025 16:54:49 -0600 "K9SW via groups.io" <K9SW@...> wrote: Thanks, Chuck. I’ve tried many variations, factory reset, restarts,
using SWR meter and dummy load, so no high SWR concerns. Still no
output or input. I’ll work on it some more and see what else happens.
It came from Mugla with the sheet listing all the power outputs on
each band, so it was transmitting at one time.
73,
Dave
On Jan 14, 2025, at 6:37?AM, Chuck Harris via groups.io
<cfharris@...> wrote:
The QMX has a protection circuit that will shut off
the transmitter if the supply voltage is dangerously
high, or too low.
It will warn you by flashing the battery symbol on the
front panel.
I don't know if it is right, but if my QMX+ shuts the TX
down for high VSWR, it loses sidetone too.
The sidetone and the TX power won't come back until you
cycle the radio off and then back on.
Perhaps, the same is true for over voltage shutdown?
Try strapping on a dummy load, applying 12.0V cycling the
power, and see if your sidetone comes back.
The radio is not amused by over voltage, or over VSWR,
but it usually, it will survive if the insult isn't too
bad.
In any case, automotive batteries, and automotive chargers
are verboten for the QMX. It doesn't want to see anything
over 12.0V (9.0V if it was built for 9V).
-Chuck Harris, WA3UQV
On Mon, 13 Jan 2025 18:23:21 -0600 "K9SW via groups.io"
<K9SW@...> wrote:
Hello all.
I bought a built QMX, being in my early 80s and not quite up to
building a complex QRP Labs kit. When it arrived, I unpacked it
and plugged in the PS IO use for the K3. Looking at the panel, I
saw the blinking battery symbol and after some rtfming, plugged in
a 12 VDC PS. However, the QMX+ has major problems, some as quirky
as a sidetone which is sometimes there, sometimes not, and major
problems such as it does not receive or transmit any RF energy
(and it’s not in practice mode). Would ten seconds of 13.8 volts
cause this amount of disfunction?
Thanks,
Dave K9SW
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Problem with 50 Watt amp for QCX
Dear Folks:
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I have finished building the 50 watt amplifier kit for the QCX.? I am trying to run the test on page 66 of the manual which simply requires you to do the following:
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1)? Make sure that the R5 potentiometer is fully counterclockwise.?
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2)? Put the QCX in "Practice" mode so no RF is generated, but the radio will generate a voltage to key the amplifier.
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3)? After keying the amp via the QCX, measure the current draw between the amp and its power supply.
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4)? Once you have keyed the amplifier via the QCX and measured the amp's current draw, R5 is gradually adjusted clockwise until the current draw begins to rise.? Once you see the current draw rise, you turn R5 back to the level just below the point at which the current draw rises.? That is the correct setting for R5.
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I have done all of these procedures.? I should mention that the green "on" light comes on when power is supplied to the amp and that the red TX light comes on when I key the QCX.? The current draw measurement is 74 MA.? Unfortunately, the current draw never changes even when I turn R5 fully clockwise.
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I should mention that I did try the same measurement with the QCX practice mode turned off, i.e., the QCX would now be generating RF.? At that point I found that turning R5 gradually changed the current draw from about 97 MA to about 103 MA.? However, no RF is generated (though the QCX generates about 4 watts when it runs barefoot).? This makes me think that R5 is functional.
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Does anyone have any suggestions for locating the problem?
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Thanks and 73 de Bernie, KF0QS
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Thanks, Chuck. I’ve tried many variations, factory reset, restarts, using SWR meter and dummy load, so no high SWR concerns. Still no output or input. I’ll work on it some more and see what else happens.
It came from Mugla with the sheet listing all the power outputs on each band, so it was transmitting at one time.
73,
Dave
toggle quoted message
Show quoted text
On Jan 14, 2025, at 6:37?AM, Chuck Harris via groups.io <cfharris@...> wrote:
The QMX has a protection circuit that will shut off
the transmitter if the supply voltage is dangerously
high, or too low.
It will warn you by flashing the battery symbol on the
front panel.
I don't know if it is right, but if my QMX+ shuts the TX
down for high VSWR, it loses sidetone too.
The sidetone and the TX power won't come back until you
cycle the radio off and then back on.
Perhaps, the same is true for over voltage shutdown?
Try strapping on a dummy load, applying 12.0V cycling the
power, and see if your sidetone comes back.
The radio is not amused by over voltage, or over VSWR,
but it usually, it will survive if the insult isn't too
bad.
In any case, automotive batteries, and automotive chargers
are verboten for the QMX. It doesn't want to see anything
over 12.0V (9.0V if it was built for 9V).
-Chuck Harris, WA3UQV
On Mon, 13 Jan 2025 18:23:21 -0600 "K9SW via groups.io"
<K9SW@...> wrote:
Hello all.
I bought a built QMX, being in my early 80s and not quite up to
building a complex QRP Labs kit. When it arrived, I unpacked it and
plugged in the PS IO use for the K3. Looking at the panel, I saw the
blinking battery symbol and after some rtfming, plugged in a 12 VDC
PS. However, the QMX+ has major problems, some as quirky as a
sidetone which is sometimes there, sometimes not, and major problems
such as it does not receive or transmit any RF energy (and it’s not
in practice mode). Would ten seconds of 13.8 volts cause this
amount of disfunction?
Thanks,
Dave K9SW
|
Mike,
?
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plus: in a big forum like this one, you mainly hear the squeaky wheels ;) And in most cases, the squeakiness is due to builders' mistakes (admittedly, modulo the few mysterious PCM1804 failures, as pointed out earlier).
?
The QMX+ is an excellent, unique rig.
?
My2Cents
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72/73 de M0KTZ
?
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Re: Your QMX output experiences @12volts...?..and by the way, what an amazing radio.
Thanks Don,
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This is new information to me. I did not look beyond the red and black pairs. I did think about color coded wires. I am using 14 gage red and black wire. Those other combinations would help.
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In this list of messages is a fresh new assertion that the QMX will absolutely puke with more than 12.0 volts applied. Maybe some day I will change my mind but for today I will avoid any "12 volt" radio that puny.
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Onward with the QCX and other tough radios.
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73,
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Bill ?KU8H
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How is the SSB progress going? Can't wait!
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Re: Best QMX AGC settings?
I'm still searching for the perfect AGC settings lol.
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How much current is flowing on the 12v line? If very little then maybe the regulator?is bad. If a lot of current is flowing and the regulator is getting hot, then there is a short on the 5v line. Please verify which is the case. Also look at the soldering on the pins of the regulator
On Tue, Jan 14, 2025 at 12:52?PM Martin AC1LL via <mshell52= [email protected]> wrote: Thanks for this.? I saw that the on/off switch was not well soldered. Fixed that, Now the LCD lights up, but no text (tried turning R47 to no avail).? I read 12v between the input of the regulator and ground, but 0v between ground and the output.
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Thanks for this.? I saw that the on/off switch was not well soldered. Fixed that, Now the LCD lights up, but no text (tried turning R47 to no avail).? I read 12v between the input of the regulator and ground, but 0v between ground and the output.
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The only issue thats in the "shadows" and not explained is dead pcm1804 IC either on first poweup/DOA or during the use. My qmx+ was in this group. After replacing the IC no issues.?
Other issues are mostly solved and related to assembly/operator/antenna errors.
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Re: QMX+ Output Power Adjustment
Unfortunately there is not yet a firmware control to adjust the output power during operations.
The hardware capability is present, so we can hope for a future firmware update that will allow us to change the % of full output power we want to use.? (Currently that is only available for 'tune' mode).
Stan
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Re: QMX+ Output Power Adjustment
Larry,
The output power is affected by the input voltage, within limits. If you have a QMX+ that's built for 12 volts, then the highest voltage you should power it with is 12 volts. The transmitted output power is going to vary a little from band to band and from build to build. I get about 4.5 watts out on 30 meters, but about 3 watts on 10 meters. I can use a buck converter reduce my input voltage to as low as 7 volts. Maybe you could go a little lower than that, but it seems to operate reliably at that level. That significantly lowers my output power, but I can't remember now what I get on each band with that.
--
73, Dan - W2DLC
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QMX+ Output Power Adjustment
I'm on the verge of buying a QMX+; the technology is just too good to pass up!? I had misgivings about the QMX because it didn't cover every band and also because of its small size. ?My camping and backpacking days are long over, and everything I do now is from the comfort of my home shack.
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My main mode of operation now is FT8/FT4, and I'm using my FT-817 for that. ?My intent is to try the QMX+ in that role. ?
On the '817 you can select different RF output levels by cycling through the available levels using a function button. ?I generally start a contact using 2.5 watts and then bump it up to 5 watts if there's difficulty in completing the contact. ?Just pressing the button once changes the power to 5 watts. ?
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I don't see anything like that on the QMX+. ?
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So here's my question: How do you change the output power on the QMX+? ?Is there a menu function to select the power? ?Or can the output power only be adjusted by changing the supply voltage? ?What's everyone else doing; do you just leave it at the same power level, or are you using some means to adjust the output power as needed for each use??
Larry, WA2VKG
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Martin, first check the 5v output of the voltage regulator (IC11). Next, look at the cathode end of D3 near the front left side of the board. You should see your 12v input there (less the diode drop). Also make sure the D3 cathode is toward the front of the board. If all of that is well, then it is likely that you have a bad solder joint or two associated?with?the 90 degree pin headers and/or the sockets on the front panel board. Or an issue with the on/off switch. Try those spots and let us know what you find ... 73 .. .Ron
Just finished the build. Nothing at the LCD. No voltage at pin 3 or at any lead of R47.? Would appreciate some guiidance as to how to troubleshoot.
Thanks
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I'm just reviving this thread to see if others have had any further success with the 50w Amp. I went around the horn a couple times until I remembered reading something about this. I had issues with erratic, low tx out of the amp when connected to the QMX. Aftew going through one end of the amp to the other--including replacing the 4.7k POT with a multi turn variety, same results.?
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On the qcx mini, it works flawlessly as designed at about 23 watts, 13 volt supply.?
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I have re-read some of the comments here but don't quite understand the issue causing this problem; the ptt is putting the amp into transmit, 4 watts input to the amp and dummy load and Bird 25w slug...power jumps around from 10-15 watts out, but very erratic. Just curious whats going on (SWR safety is disabled)...its as though the qmx is throttling back on the input power?
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If nothing else I have re-confirmed the amp works A-OK with the qcx as designed...
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Scott vy1co
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Re: QMX and QDX - Not enough 5V PTT oomph
Sounds like a great plan, let us know how it turns out.
Be sure to measure your PD outputs if you try to use multiple voltages from the same power bank.? My power banks wont switch one port to 9V/12V with a trigger cable, and simultaneously output 5V on the other port: as soon as I plug something into the USB-A port, the 12V triggered output switches down to 5V also.? I understand some power banks do support independent voltage output, but you need to find it in the specs.? Or just use your second power bank like I do.
Stan
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Hi,
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IMHO design and instructions for all QRP-Labs is exceptional and this is also often reason for many troubles and issues you see on the forum.
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I personally build 2 QMX and both times all was working straight off the bat. It is true that some tweaking with LPF/BPF is needed to get good results but this would happen with any kit available on the market. QMX is no different to uSDX, (tr)uSDX or mcHF in that respect.
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In the earlier days there were issues with blown finals but this is user errors (99%) now days software has protection build in so all you need to do read manual and switch it on. Still many builders fail to do that.
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QMX by design is portable rig, but to me it is a bit fragile electrically for that. What I mean that all needs to be connected in the right way and switched on at right sequence other wire you can blow your power supply or other parts. This is the only gripe I have. I still love these radios and repaired mine twice already but I want to use it and not have it in bits on my workbench.?
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When I say fragile I mean pulling power plug before switch off should not be a problem, connecting equipment (PA) in wrong moment also. So as long you do not ruch (as I do) and follow procedures you will be fine.
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---------------------------------
73 de Marek SP9TKW
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Re: Best QMX AGC settings?
I noticed the crackling noises when I was operating this weekend, using my new AGC settings.? They seemed to happen when the AGC was not engaged.? In other words, I heard crackling when the signal was weak, and the audio was better when the signal was strong.? For the record - I really like my new settings, especially when I hit a birdie!
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| Threshold |
4 |
| Slope |
80 |
| Noise |
10 |
| Hang |
30 |
| Smooth |
50 |
| Recovery |
10 |
| Sample |
2 |
| S9 |
S6 |
| AGC display |
ON |
| AGC dB per bar |
3 |
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73,
Mike, KL7MJ
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Mike,
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I too had the same trepidation about buying the QMX+ kit because of the number of folks posting their issues. ?After looking at the posts, I realized that a great many were user caused issues related to soldering, wrong part placement. Etc. ?without knowing the total number of kits built, the number of non- builder issues is just a vocal minority. ?
although I did not post my issues with the kit build, I suspect that I am part of the majority that just didn’t solder as well as I should have. ?The built in diagnostics and post from the great and knowledgeable folks like Stan and Ludwig saved me from the embarrassment of needing to post for these common problems.
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my advice is that if you are inclined, go ahead and get a QMX+. ?There are plenty of folks to help you get a working device if it doesn’t fire up immediately?
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Len KJ9E
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Ronald Taylor
Ivica - YU1QRP
Daniel Conklin
Marek SP9TKW