Re: Max Voltage for QMX 9V
There doesn’t seem to be a clear consistent answer, the manual implies “a little over” is OK but does not define “little”. I admit that I don’t understand how a device that can handle 12v can’t go over 9v.
I do know that I have made contacts quite well with just 2 Lion 18750’s and they last for the duration of the park operation. ?The output is <4w, not a big deal.
Until we really know, just play it safe, many ways to keep the voltage under 9v.
John KK4ITX ? ?Each mistake is a learning opportunity.?
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On Mar 30, 2025, at 7:59 PM, Daniel Conklin via groups.io <danconklin2@...> wrote:
? You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range.
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73, Dan - W2DLC
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Re: Max Voltage for QMX 9V
You could use 2- 7809's in parallel for added current rating or 1-78S09, which I think is good for 2 amps by itself. Your input voltage just needs to 3 or 4 volts higher then the needed output voltage.
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Dave
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Re: Max Voltage for QMX 9V
You could put a small buck converter or a couple of diodes in the line to drop the voltage into acceptable range.
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73, Dan - W2DLC
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Re: Max Voltage for QMX 9V
I wouldn't use FT8, but CW into a well-matched antenna might be ok...
XE3/VA3RR
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Hello,
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I have a QMX that is built for 9V. Now I'm making a custom LiFePO4 battery for it. My question is, what's the maximum input voltage that the QMX can handle before it breaks? Given that each LiFePO4 has around 3.55V, if I connect three of them in series, I'll get around 10.65V, is that going to damage the radio??
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Thanks,
Sepehr N6IRN
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Apparently this microphone works best:
/g/QRPLabs/message/141854
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Jerry, KE7ER
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On Sun, Mar 30, 2025 at 11:20 AM, Stan Dye wrote:
Yes, the SSB software works on all QMX devices, but not QCX or QDX.
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And you got a good microphone.? I just assembled my kit from Erik and the mic element he is providing is much better (higher sensitivity and dynamic range) than any of the other 3 or 4 electret mics I have tried.?? Which results in being able to use a lower mic gain and having lower tx noise.
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Stan KC7XE
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Re: 74ACT08 damaged and LCD is all blocks
Chris,
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Not clear what you were doing there.
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Strikes me as a very bad idea to apply reverse power to the QMX from your power supply, if that is what you did.
You could wind up with a whole bunch more problems to diagnose.
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There are far better ways to find an open solder joint.?
Use your ohmmeter, or power up properly and use your voltmeter.
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And if I want to see the volts across a diode, I'd just use the voltmeter function of my DVM.
Diode Test mode is meant for use when you have a diode sitting loose on the bench (no power supply on it)
and want to have some rough idea if it functions.
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This got me curious though, I had never used Diode Test mode with this meter.
On my DVM in Diode Test mode, it seems to apply 3.3v to the device under test through a 1.9k restance,
and reports the voltage it sees across the diode.? The red probe is positive.
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Jerry, KE7ER
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On Sun, Mar 30, 2025 at 11:23 AM, Chris wrote:
one way to check the power connectors is to use a meter in diode mode with the power reversed so I can see the 0.6V drop across D110 the surge protection diode.?
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Re: QMX V4 will not mount
On Sun, Mar 30, 2025 at 04:56 PM, Jim Brown wrote:
it draws 40ma
Hi Jim, wrong, 0 mA in this state and around 200 mA for a part of a second when firmware is running and for the whole time in firmware update mode.
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You may read QMX QMX_plus Startup to find more information about the start process and what to check for debugging. ?
73 Ludwig
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Re: Qmx plus rev 2 not powering up
On Sun, Mar 30, 2025 at 08:03 PM, Azgael wrote:
God knows how many other tracks or vias are open or broken.?
I would be surprised if this connection is broken.
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Re: Qmx plus rev 2 not powering up
On Sun, Mar 30, 2025 at 05:41 PM, Azgael wrote:
following the voltage path I should have the 12v on the vin of IC101 but nothing arrives there
Hi Azgael, yes, drain of Q102 and VI of IC101 must show the same voltage.
But 5 V at drain of Q101 is strange. If the controller doesn't work the gate of Q101 is pulled to 50 % of "+12V", so here around 6 V. In this state drain of Q101 should have something close to 0 V and not 5V. I would check the reason for this.
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73 Ludwig
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Re: 74ACT08 damaged and LCD is all blocks
Han, fine if I could get a little help. And you made good investigations to find the problem, well done! Thank you also for this information.
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73 Ludwig
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On Sun, Mar 30, 2025 at 08:37 PM, <ng433@...> wrote:
i discovered that the Lin_Reg_EN signal is stuck at .7 volts with 10V in
When left encoder is pressed?
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How did you test the SMPS boards, using the method from the QRP Labs Wiki?
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When the controller isn't running, LIN_REG_EN is pulled to 50% of "+12V". With 10 V in it should be around 5 V produced by R101 and R115. If the voltage is near 0 V LIN_REG_EN is disabled and no VDD is produced to start the controller.
0.7 V could come from a broken Q101, a broken Q110 or a fault at the mainboard. I recommend to remove all the subboards and check resistance for the mainbord VDD - GND and VCC - GND. Both should be some kiloohm. If only a few ohm something is wrong connected to the low resistance voltage rail.
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73 Ludwig
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Re: QMX+ "Tune SWR" for 1 second?
Hi Fred
I expect WSJT-X is querying and setting the radio via CAT commands. I should change that! Consider it added to my list!
73 Hans G0UPL
A puzzle resolved?
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I tried various bands and modes, but I failed to enable my QMX+ Tune SWR function for more than 1 second,
far less than this old duffer could work an "antenna tuner" in his best days.
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Hans, in a You Tube video, shows how that function works in the QMX, continuously keying tx and showing the resulting SWR,
for up to 1 minute; sufficient time for this Ol Geezer to "tune er up".
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Being slow in the head, and getting no better, after a couple of days I "discovered" that with my QMX+ connected to a PC, connected to? WSJT, the Tune SWR only keys up
my QMX+ for 1 second and does not time out after 1 minute. When WSJT-X is closed, the function works as advertised... Now, happy old dog.
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Da Ol' Dog/wa4hei
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Re: QDX Transmit Power Drops
Thank you, that is the plan. Just waiting on the wire to arrive.?
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73 Doug WB5WRC
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LIVE: SOTA+ is trying to do SSB on 10 GHz with a QMX
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The QMX puts out 10 MHz, a transverter converts up to 10 GHz
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SO i had a working qmx rev 2 - purchased assembled - i was swapping my antenna coax from another radio and poof the QMX no longer powers up . I also had a kit so i swapped out the PS boards . Still no luck . i tested the power supply boards individualy and they work fine . After furthur trouble shooting i discovered that the Lin_Reg_EN signal is stuck at .7 volts with 10V in . I tried tacking a pull down resistor ( 10k ) to ground and it lowered it by maybe 20 millivolts . Sounds like i have a bigger problem . Any suggestions
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Re: 74ACT08 damaged and LCD is all blocks
I seem to have dodged this bullet, or something very similar.
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While powering up my QMX+ for the first time noticed that although it powered up the supply was current limiting.? Tried increasing the limit and ended up at 380 mA, then found that the limit was increasing and one bank of BS170s were getting hot.
I was also finding that the QMX+ would shut down spontaneously. just touching things seemed to cause this and sometimes I was getting high current and sometime not.
I began to suspect the power supply, maybe the connector or my plug.? After a lot of fiddling around - one way to check the power connectors is to use a meter in diode mode with the power reversed so I can see the 0.6V drop across D110 the surge protection diode.? Something definitely wrong, sometime 0.6V, sometimes nothing, as in no connection.? The solder joints looked perfect but reflowed them anyway and everything started looking normal.? Now everything seems fine, no high current when in receive and after reflowing a few more joints everything seems fine. I'm getting just over 1W output running at 7.5V.
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I've seen all sorts of bad behaviour when a processor gets short power drops - negative spikes - and wonder if the TX line to IC503 became active with CLK2 not running.? This would have turned one bank of BS170s on and as they heat up the current increases but my current limited supply protected then and everything else.
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Initially I was seeing low power output, 0.4 to 0.6W seemed low, even for 7.5V and the output waveforms were different on the two banks of BS170s.? Reflowing their solder joins, after replacing T501, fixed that.
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What saved my QMX+ from damage was running with a low voltage and with a current limited supply.? Keeping the current and voltage down prevented damage while I sorted out the problems.
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Chris, G5CTH
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Yes, the SSB software works on all QMX devices, but not QCX or QDX.
?
And you got a good microphone.? I just assembled my kit from Erik and the mic element he is providing is much better (higher sensitivity and dynamic range) than any of the other 3 or 4 electret mics I have tried.?? Which results in being able to use a lower mic gain and having lower tx noise.
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Stan KC7XE
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Re: 74ACT08 damaged and LCD is all blocks
It's really nice to discover what really happened.? Great job in patience and persistence to figure it out, and not just blame the kit - it's almost always something we do that causes the failures.
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In this case, a fuse certainly would have helped.?
And one change Hans should indeed consider is to disable calibration if TX is disabled on that band.
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Stan KC7XE
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Re: Qmx plus rev 2 not powering up
Hi Zhenxing?
Thanks, I will do that! But if it works, God knows how many other tracks or vias are open or broken.?
will be able to do it only tomorrow but will keep You posted.?
BR
Azgael
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KK4ITX John
W6MQI
Daniel Conklin
va3rr