I have proven that it is possible to fry IC402 with too much RF on the input side. :(

Did you have an antenna connected to your QMX while you were transmitting with another radio ?

73,
Steve, N2IC

How are you powering it? I had an issue similar to this when the buck-boost converter that I was using to limit input voltage was silently clipping the input current (due to a bad setting on my part)

Greg, KB1UGP

Just a quick update regarding my issue with the LCD:

I ended up sending the rig to Jeff Moore, W1NC, for further inspection. He did an AMAZING job of troubleshooting and fixing the LCD data connection. There was a broken PCB trace which he substituted with a jumper wire. Not only did he resolve the LCD issue, but he also spotted and fixed a couple of other issues with the TX and SWR meter capabilities of the rig.

I have made several QSOs with the QMX and I cannot emphasize enough what a great piece of kit it is.

I would like to note that Jeff Moore provides this service at no cost, only charging for shipping and parts. Out of kindness and emphasizing the notion of "Hams helping Hams," he does not demand any money for the valuable time he puts in. Please, if you end up sending him a rig, consider donating, as he dedicates all donations to maintaining a reliable inventory of parts to continue this great service for the ham radio community.

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"why one would need to have audio on in Digi modes?"

I disagree, though I agree that some would not!

My ear can't decode the signals, but I can hear how everything is going. Agree, that it's elsewhere in the displays. But if I'm listening, I don't have to search it out.

Just sayin'. OK that YMMV!

73, Paul -- AI7JR

-- 
Paul -- AI7JR

On Thu, Jul 11, 2024 at 05:32 PM, Bojan Naglic wrote:

A thought: I wonder why one would need to have audio on in Digi modes? Just mute it.

I find it useful if I am trying to debug another radio setup (listening to the signal coming from the other radio).? Definitely prefer that audio remain available for listening in digi modes.

I have 2 factory built QMX's, a Hi & a Low Band. They are used for DATA comms only.
Recently the Low Band radio has been acting strangely.
When it begins to TX it gives a pulse - the TX bar graph goes full for a second or so, then back to nothing, then back to transmitting as normal.
It is doing this on all bands though the worst seems to be 40M.
Power out is showing as 4.9W (The same as on the factory test paperwork)
Occasionally the TX bar graph & output "stop" at around 4 seconds into the TX cycle.?

My antenna is less than 1:1.3 across the bands - but the operation is the same when connected to a dummy load.
Changing between battery & different power supplies makes no difference.
The Hi Band radio does not have this "stutter"& works flawlessly.
I have tried different USB ports, Software, Cables, RF Chokes, Clip on Ferrites, etc.

The radio is still making FT8 contacts - it is just that it has this "stutter" at the start of the transmission & sometimes drops out part way through the TX sequence.
Anyone have a suggestion..??

Cheers
Rob
VK5ZIK

WB0ZJJ-Alan via groups.io wrote:

I managed to build my QMX successfully, and in
two days of playing with it fried the receive
function. W1NC Jeff Moore diagnosed and
returned the radio to full function:

[Quoting W1NC e-mail:]

IC402 was destroyed. I used to see this
frequently in Rev 2 QMXs. But this is a first
for a rev 4 unit. It's hard to say why this
happened. Usually it is from back EMF when
switching from TX to RX mode. But there is a
protection diode in place for that after Rev 2.

For those of us who have early QMX units with Rev 1 or Rev 2 circuit boards, is it wise to modify the board to install the protection diode that is now included on current Rev boards?

Hi Ludwig,
I think the time sync has to be done correct and not just at the about right maner. Bseides one can observe the spectrum to get the information about the start.
For the use of the wide band audio for the RX I proposed to introduce the third mode which would than also switch the frequency to the last heard SSB signal and not stay on the Digi band.
--
73 Bojan S53DZ

Thanks for putting that on Hans! Learned a few things from your slide show as well as some insider info I didn't know.

If you are a QRP Labs fan (as most here are) this is a must watch if you aske me!

Been running the pants off my QMX+ for several weeks on ft8 around 3.5 watts into an OCFD. It worked right off the bench but I didn't HIHI! Numerous low Z between the headset moments and RTFM issues...

73
-Mike

I managed to build my QMX successfully, and in two days of playing with it fried the receive function.? W1NC Jeff Moore diagnosed and returned the radio to full function:

IC402 was destroyed. ?I used to see this frequently in Rev 2 QMXs. ?But this is a first for a rev 4 unit. ?It’s hard to say why this happened. ?Usually it is from back EMF when switching from TX to RX mode. ?But there is a protection diode in place for that after Rev 2. ?I tested that and it seems ok. ?Your power out is high compared to many other QMX rigs. ?Maybe if you backed down the voltage to 11 volts or less, it might help prevent that in the future.

?

...

Here is what I found and did:

?

1) Disassembled all boards, cleaned with 99% IPA

2) Inspected under 10X stereo microscope

3) Tested on bench AF, image scan and rf scan functions - all found to be very poor

4) diagnosing on the bench found IC402 bad - replaced that chip

5) retested on the bench AF, image scan and rf scan functions - all found to be 100% now

6) Tested TX functions on all bands at 12V.? At 12V power out is 3.6 - 5 watts depending on band - no attempt was made to optimize beyond that

7) reassembled into case and retested everything one last time - now 100% RX, TX all modes, all bands

?

Total time spent - about 2 hours

I had fun this morning snooping on tons of FT8 on 17m using a z-matched random wire indoors.? Weather is a bit wet to string up my outdoor antenna just yet.

Thank you Jeff.

72s?

On Thu, Jul 11, 2024 at 11:48 PM, Bojan Naglic wrote:

But again why would you like to listen to the jam of the Digi modes signals?

If I don't have a proof of time sync listen to the audio and watch the computer clock gives me a first impression of sync.
And in the moment Digi is the only way to listen to SSB I think.

73, Ludwig

... what I want to say is that the audio volume of one Continuous Wave signal in BW of 300 Hz is about equal to the SSB signal in the 3kHz BW. Considering the characteristics of a SSB signal.
But you are correct as you have done with this -20dB attenuation in the Digi mode, for instance FT-8, you can have 100 different carriers of a comparable power adding up in the 3 kHz BW (+20dB). But again why would you like to listen to the jam of the Digi modes signals?
--
73 Bojan S53DZ

Yes, that is the way to do it. These display's backlight is really bright. I have even used greater resistor there.
--
73 Bojan S53DZ

On Thu, Jul 11, 2024 at 08:17 PM, Hans Summers wrote:

?

2. Add 20dB of attenuation in earphones when in Digi mode (equalize volume to CW)

Stops you being accidentally deafened if you change from CW mode to Digi by mistake. Surely there must be some way to calculate given a bandwidth difference, what the perceived volume difference would be... in the absence of having a sufficiently functional cerebral cortex I just found that 20dB sounds a lot better than nothing at all.?

?

Hi Hans,
thanks for this FW release.
A thought: I wonder why one would need to have audio on in Digi modes? Just mute it. And enable the audio in the third (not yet there) mode to have the choice of an RX broad band audio on to listen to SSB signals.
?
--
73 Bojan S53DZ

Good stuff, Randy!
Those toroids really are self shielding!
--
73, Dan? NM3A

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GA Bill,

Maybe you can replace R306 (33 ohm) on the front panel board with a small 100 ohm pot to adjust the brightness. I was thinking of doing it for my QMX (not plus) not necessarily for the brightness but for minimizing the current consumption from the backlight.

73,
Yoon KM6KJI

Thanks Hans, a self calibration feature would be great. My QMX+ is just under 1W on 6m and I would like a bit more, that is quite a lot under spec..

Thanks for all your efforts..

73 Dave G4FAW?

Does anyone have an easy safe method of dimming the backlight on the QMX+
Perhaps changing/adding a resistor.
The bright backlight is fine in a well let room or outdoors but in my dimly lit
bat/ham cave it’s hard on the eyes.
Thanks, Dave