Power Failure on New Factory-Assembled QMX+
My assembled QMX+ arrived from QRP Labs on Monday 24 March and today I have a problem.?
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I powered the rig on and keyed my paddles, but heard only one dit before an 'S' displayed on the screen (high SWR).? The antenna is resonant (see below) so I powered off the QMX+.? Powering on again, I heard static briefly in my headphones but the display would not light up.? I tried a couple more times to power on, with same result.
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Two days ago I connected an EF-15 end-fed tuned dipole via 15m of Mini8 coax to the QMX+ and was calling CQ.? I got no response but I saw on the RBN that my signal was picked up in Vermont with 9dB snr--from Ireland.? So I know the antenna is OK and I'm using the same setup today.? I know the power to the QMX+ is OK--it is using a battery that today reads 11.8V output on my WattsUp in-line power meter.
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I'm not technical and wouldn't trust myself to measure components, etc--and this is a brand-new QMX+ assembled and tested in Turkey.? Would anyone have suggestions what to do next?
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Many thanks in advance for any ideas,
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Tim Ei2KA
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Re: Old QCX Classic 30m build
I built several of the original ones, you should be good. Build it.?
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On Mar 27, 2025, at 12:35?PM, w0wly via groups.io <w0wly@...> wrote:
? Good Day,
Inquiring as I read somewhere in all my reading on here that some of the original QCX classic kits had different cores and where replaced to include "better" maybe cores later on.?
I bought and put together a classic for 40m and it was my first HF radio and my first QSO was on it. I also bought one for? 30m band at the time as an incentive to upgrade from my technician license. Figured i'd build it when i upgraded. Well, in the mean time i have built some QDX's and a couple QMX's but I still have this 30m classic and bama case to put it in. Just upgraded my license two weeks ago and I'm eyballing that 30m classic to build it now.?
Question is:
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It's a rev3a I believe without checking, do I need to get replacement cores or did it ship with good ones? If i remember correctly it was two different parts sources but my recollection is foggy. My 40m radio seems to work fine so I'm thinking it was an earlier issue but figured I'd ask!
Thanks!
Ryan?
w0wly
--
Gary W0CKI
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Re: Toroids: Do I have these sorted correctly?
#QMXplus
That’s what came with the kit. Just follow the instructions.?
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On Mar 27, 2025, at 9:41?AM, avinoam83 via groups.io <avinoam83@...> wrote:
? Thanks! <20250326_183259.jpg>
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Gary W0CKI
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Old QCX Classic 30m build
Good Day,
Inquiring as I read somewhere in all my reading on here that some of the original QCX classic kits had different cores and where replaced to include "better" maybe cores later on.?
I bought and put together a classic for 40m and it was my first HF radio and my first QSO was on it. I also bought one for? 30m band at the time as an incentive to upgrade from my technician license. Figured i'd build it when i upgraded. Well, in the mean time i have built some QDX's and a couple QMX's but I still have this 30m classic and bama case to put it in. Just upgraded my license two weeks ago and I'm eyballing that 30m classic to build it now.?
Question is:
?
It's a rev3a I believe without checking, do I need to get replacement cores or did it ship with good ones? If i remember correctly it was two different parts sources but my recollection is foggy. My 40m radio seems to work fine so I'm thinking it was an earlier issue but figured I'd ask!
Thanks!
Ryan?
w0wly
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Re: QMX+ Strange Audio Artifact - Help, Please...
Took a deep breath and removed C504. It measures about 500 uf so this cap is fine. No problem re-installing it. Other than my shaky hands!
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I did find an interesting thing while doing the testing. I had been using an Astron VS-35M p.s. in the shack into a boost-buck device set to exactly 12 v. It also shows current but I've found that to be completely bogus. Today I took the QMX+ to the garage workbench and connected it to my benchtop p.s. which is a lot more accurate than the boost-buck and is capable of current and voltage limiting. With it set at 12.0 v I did a key down on the QMX+. The output voltage stayed at 12.0 or so, but the constant current light and constant voltage light both flickered - and at the exact tempo as that machine gun sound on my headphones. Strange. I unhooked the radio and replaced it with another QMX+ that I built last year that works perfectly. No machine gun audio on key down and no flashing lights on that bench p.s.
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At this point I may have reached the upper limit of my debugging ability. Perhaps the only other thing I could try would be to remove D502 and test it, although it is a lot smaller than that tantalum cap and might prove tricky for me to attack.
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If you guys think it's worth testing that thing I'll give it a try. Or if there is something else that is within my capabilities... Otherwise it might be headed to Jeff for a New England vacation.
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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Re: mic test doesn't scroll up
On Wed, Mar 26, 2025 at 08:38 AM, Stan Dye wrote:
I think securecrt is way overkill
It sure is! However it's useful for other stuff, and then I only need one console application. :) Fortunately for me, securecrt is not the problem.
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I believe I've gotten to the bottom of this thanks to your clue about screen size. Same issue with minicom under linux running in gnome terminal. The width doesn't matter. But the number of rows need to be 25 or less. In fact if I resize the terminal window while "mic test" is running, it suddenly starts scrolling at 25 rows or less. At 26 rows and greater, the window clears and only the bottom row of "mic test" is shown.
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It's interesting that this is the only QMX menu that is dependent on rows of the console in which the terminal emulator is running. Certainly all the menus show only 24 rows, but all the various graphical displays work regardless of my console's configuration with the exception of "mic test".
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Very satisfied with the SSB audio
Here my initial test of the audio,? sry in German :-)
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73 Chris?
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Re: Available Hand Mics for QMX SSB ?
The mic supplied with the FX4C works with the QMX, no adaptors required. The one Erik is making are prob better though.
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Compton
VK2HRX
Sydney, Australia
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Re: QMX Electret Microphone specs
Frome the QMX SSB page at QRPlabs
"All development has been done with this particular Electret microphone from Digikey, part number 668-AOM-5024L-HD-F-R-ND:
This is NOT the same microphone as the QMX supplied onboard microphone. Many thanks to?Paul?W9PEM who gifted me this microphone, beautifully enclosed with a PTT button and 3D printed enclosure."
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Here's how microphone sensitivity is measured:
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A lower negative dB (such as -24dB) means more Volts out of the microphone for a given sound pressure
than a higher negative dB (such as -44dB).
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The spec might use units of dB, dBA or dBV for the gain.
My guess is that these units are all directly comparable.
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Mouser has a selection of 179 different electret microphones:
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Selecting for only those with a sensitivity better than 30dB gives 11 microphones:
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Three of those are not in stock, and two of the remaining expect a supply greater than 3 volts.
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SNR is not given in the selection summary,? it is spelled out as "signal to noise" in the datasheets so search for "noise".
Of the remaining 6 microphones that have a sensitivity better than -30dB, the SNR is generally 60 or 70 db.
The two from PUI claim 77 and 80 dB of SNR, and are the most expensive at around $3.
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If Hans really does use -24dB microphones with an 80dB SNR, those are not typical of what's on the market.
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Jerry, KE7ER
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Re: QMX Electret Microphone specs
Here's how microphone sensitivity is measured:
?
A lower negative dB (such as -24dB) means more Volts out of the microphone for a given sound pressure
than a higher negative dB (such as -44dB).
?
The spec might use units of dB, dBA or dBV for the gain.
My guess is that these units are all directly comparable.
?
Mouser has a selection of 179 different electret microphones:
?
Selecting for only those with a sensitivity better than 30dB gives 11 microphones:
?
Three of those are not in stock, and two of the remaining expect a supply greater than 3 volts.
?
SNR is not given in the selection summary,? it is spelled out as "signal to noise" in the datasheets so search for "noise".
Of the remaining 6 microphones that have a sensitivity better than -30dB, the SNR is generally 60 or 70 db.
The two from PUI claim 77 and 80 dB of SNR, and are the most expensive at around $3.
?
If Hans really does use -24dB microphones with an 80dB SNR, those are not typical of what's on the market.
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Jerry, KE7ER
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Re: QMX Electret Microphone specs
Mic Output levels... The -44 db Spec is due to the modern digital devices today, so that the Mic doesn't overdrive the?ADC/DAC, as used in most?modern SDRs, as well as SmartPhones/Tablet/Notebook PCs.?? In other circuits (e.g. FM Modulators) it's usually not an issue.? That said a Mic with output of -44 db will drive an older ICOM analog (traditional heterodyne type SSB transceiver), to proper ALC levels with the Mic gain set near 50%.
Then there is the difference in intended use of the?Mic and there are three types of Mics.
1) There are consumer Electret-Condenser Mics that have these output levels with the?mic at some distance to the?mouth.?? 2) A Close-Talk, Noise-Canceling, "communications grade" (e.g. Aviation Mics) that level is reached with the?Mic centered in front of your mouth with it set at 1/8" from your lips.? Then the acoustic noise cancelling?works, and the?output levels are maintained. 3) Now typical Studio Electret-Condenser?Mics?are yet different again with 48V "Phantom Power" (rather than 5V through a 4.7K ohm resistor for Mic BIAS).? This likely came from the AT&T networks that provided communications from the studio to the transmitter, but I'll confirm that with Dave, WJ6W he knows this stuff.
Collins Radio set the?standards for Aviation radio interfaces, and those interfaces are still used today (.206" Mic plug to differentiate it from the .250" Headphone Plug) with a high impedance Dynamic Mic.? Today the modern general aviation radios all use Electret-Condenser Mics (600 to 2K Ohm Mics). The exception is a military helicopter headset where the Mic is typically a 5 Ohm Close-Talk, Noise-Canceling, Dynamic Mic due to the extreme noise levels they must contend with.
Dave WI6R
On Thu, Mar 27, 2025 at 8:33?AM Daniel Conklin via <danconklin2= [email protected]> wrote: Tony,
I know from working in the audio/video production industry that there are high quality and low quality electrets. Usually, but not always, you get what you pay for. Mine is a cheap Baofeng mic, however, After doing the gain adjustments, my input audio curves looked pretty close to the ones Hans provided.?
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73, Dan - W2DLC
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Re: Difficulty after loading ssb firmware beta 1-01-03 on QMX+
On Thu, Mar 27, 2025 at 02:29 PM, Daniel Conklin wrote:
to just copy or drag
copy yes but never drag. There were reports about problems after drag the FW into the QMX folder.
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Re: Difficulty after loading ssb firmware beta 1-01-03 on QMX+
It is never necessary to delete the current firmware from the QMX, but I don't know if it is a failure mechanism
Gary
W9TD
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
On Thu, Mar 27, 2025 at 11:23 AM, Mehmet Dinch wrote:
The audio sounds like the QMX is only picking up the peak signals from my voice.
...
Adjusting mic gain to about 70 seems to improve the audio. However, every time I key up,? there is now an awful lot of noise before I even start speaking. Once I start speaking the audio is ok'ish with a load of background noise.
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73 Ludwig
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Hello Mehmet and all,
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if you need significant more than 55 dB audio gain the micro is not sensitive enough for QMX use. You will find something about this on page QMX QMX_plus SSB settings from QRP Labs Wiki. ?
73 Ludwig
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Yeah, I just took a snippet of the 20m band. :-)
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
As I said, I can't judge whether that plot looks good or bad. Some of Hans's plots looked similar. Everyone's radio will likely have different looking plots as the hardware has variations.
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73, Dan - W2DLC
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Re: SSB audio distortion #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Your band configuration page looks very different from mine. I can see all of the bands at once.
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73, Dan - W2DLC
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Toroids: Do I have these sorted correctly?
#QMXplus
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Chris
Compton
Dave WI6R
Gary W9TD
Daniel Conklin