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Re: #qmx #Heil #SSB #QMXplus #qmx #Heil #ssb #QMXplus

 

Hi,
?
I'm using a gaming headset with build in mic. I found that the mic wasn't sensitive enough as I had to set the mic gain on my QMX so high that it started to produce undesirable background noise.
?
So, decided to use an inexpensive mic preamp module, MAX9814. The module has a mic capsule soldered on the board. I removed the capsule and wired it up to my headset mic and wired in a foot switch for PTT for hands free operation.
?
Mel. M0KMD.
Re: Newly assembled QMX, SWR=1.5 with dummy load

 

Hello all,
?
My best bet is that the 50 ohm SMA load has already been overheated, changing the value of the terminating resistor, which is the cause of the 1:1.5 SWR after all.
?
73,
Roelof, pa0rdt
Re: Newly assembled QMX, SWR=1.5 with dummy load

 

Thank you all - this is sound advice. I own a dummy load, but am in a different QTH so I used what I had at hand.


On Tue, Apr 22, 2025, 07:46 Jerry Gaffke via <jgaffke=[email protected]> wrote:
I agree.
Never use those dinky 50 ohm calibration references as a transmitter dummy load.
Unless your transmitter is sending out a max of a tenth Watt or so.
?
Hans has a nice 20W dummy load for $8.50,? perhaps include that with your next order.
?
A cheap dummy load can be made with a bunch of 3 Watt metal film resistors in parallel,?
For example, four 200 ohm parts in parallel can deal with 5 Watts all day long, and cost about $0.25 each.
Mouser part number 603-RSF3WSJR-73-200R? is a good choice.
For 50 Watts, perhaps use twenty 1000 ohm 3 Watt resistors, Mouser 603-RSF3WSJT-52-1K.
?
If you already have a dummy load and want to use it as a 30 dB attenuator, you can do something like this:
?

in ---+--------R------+------- out to coax
? ? ? | ? ? ? ? ? ? ? |
? ? 50ohms? ? ? ? ? 50ohms
? ? ? |? ? ? ? ? ? ? ?|
? ? ?GND ? ? ? ? ? ? GND
?
The first 50 ohm resistor is your dummy load, it must be high power to deal with the transmitter.
R should be 1/2 Watt for a 30dB attenuator, can be 1/8 Watt for a 40dB attenuator, value of R calculated below.
The second 50 ohm resistor at the output can be 1/8 Watt.
I assume you are sending the sample out to something like a tinySA over coax.
The second 50 ohm resistor is the source termination to absorb any reflections coming back from the coax
There is a third 50 ohm resistor inside the tinySA that is in parallel with the second 50 ohm resistor,
together they make a load of 25 ohms.
For 30dB of attenuation we have a power ratio of 1000, so a voltage ratio of sqrt(1000)=31.62.
Those two parallel 50 ohm resistors in series with resistor R form a voltage divider.
To get a voltage ratio of 31.62, the value of R should be around (31.62 - 1) * 25 = 765.5 ohms for 30dB of attenuation.
For 40dB of attenuation, the value of R should be (sqrt(10000) - 1) * 25 = 2475 ohms.
Anything within 5% or so should be fine for our needs.
?
On the 30dB attenuator, having (765.5+25) ohms in parallel with the 50 ohm dummy load brings it down to? 47 ohms.
So in that case we might be better off with four 220 ohm resistors instead of 200 ohm resistors.
The transmitter now sees 55 ohms in parallel with 765.5+25, or 51.3 ohms, which is good enough for most of us.
If we then add a 2000 ohm resistor in parallel with that 51.3 ohms, we then have the transmitter seeing 50.02 ohms.
On the 40dB attenuator that additional parallel load of (2475+25) is so small it won't matter, so use four 200 ohm resistors.
At 40dB, you need to start being careful with how it's built to avoid unwanted coupling from input to output.
?
Check out that attenuator before using, as you don't want to burn out your tinySA.
I'd just hook the transmitter input port to a 12v battery, check for the a voltage of 12v/31.62 at the output
with a voltmeter.? Add that third 50 ohm resistor before measuring.
?
?
For US residents buying stuff direct from China:
In summary, the de-minimus exemption from tariffs for packages worth less than $800 expires on May 2,
at which point the minimum customs fee will be $100.? On June 2 it rises further to $200.
So you could be spending $210 for that $10 attenuator.
If you place an order now, it will probably arrive at US customs around May 2, so place your bets.
?
Jerry, KE7ER
?
?
On Mon, Apr 21, 2025 at 08:26 PM, Donald S Brant Jr wrote:
On Mon, Apr 21, 2025 at 05:04 PM, Wolfgang, DF1KZ wrote:
Are you shure that this dummy-load can withstand the output-power of the QMX (up to 5W!)?
It is also poor lab practice to use precision calibration kit standards as adapters or dummy loads.? They are precision instruments and should be given requisite care.??
10 watt 30dB attenuators are less than $20 on AMZN and likely stupidly cheap from China, they will work as a dummy load or attenuator.??
?
No ham station should be without a suitable dummy load, anyway, IMO.? Suitable meaning able to handle full output power for long enough to make meaningful measurements.
73, Don N2VGU
Re: #qmx #Heil #SSB #QMXplus #qmx #Heil #ssb #QMXplus

 

I hadn't thought of using a headset...I have a BM10ic that would probably work pretty well so I shall collect bits for an appropriate adaptor!
Re: QMX+ loose some characters while sending stored messages #qmx #QMXp #QMXplus #troubleshooting

 

to explain, i remember formerly my both `normal? QMX i programmed the messages by the rig directly, PUTTY i?m using only since i have the QMX+ ...
that?s why i stumbled about? ;)
?
vy 73 Udo DF4BJ /qrp
Re: BS170 FET

 

Many thanks.
Re: QMX: C107 burned

 

Thanks a lot to everyone for your helpful tips.

I've now removed the two SMPS boards and measured on the mainboard. The resistance between PWR_HOLD and GND is only 250 ohms. Between VDD and GND, it's only 450 ohms. I'm afraid that's not a good sign. It looks like it's a total loss.

Regarding the Talentcell LF4100: As I understand it, the 12V output is directly connected to the LiFePO4 cells. That is why the voltage there can be between 9V and 14.6V, depending on the state of charge. However, the 9V output used for the QMX is regulated. I have now measured the voltage: when idle, it is 9.09V. When I connect my first QMX, it shows 9.1V in the diagnostics menu during receiving and 9.0V during transmitting. This rules out the TalentCell as the cause.

I cannot therefore identify any external cause for this disaster. The power supply was stable, the antenna was adjusted, and the QMX worked without any problems until it suddenly failed, both during reception and transmission. It therefore broke down on its own. Very annoying.

?

73, Joerg DG0JDE
Re: QMX SSB internal mic? #ssb #qmx

 

Hi?
I am using an external mic and the beta version -003 for SSB. Even the slightest tap or shuffle on the desk with my QMX+ causes the VOX to trip. I am confident the external mic is not causing the VOX to trip. Would Hans spur removal still work if I removed the QMX+ internal mic and would that get rid of the unwanted VOX trips? Or do you think Hans could isolate the internal mic from the VOX detection in firmware?
I noticed the same issue, but raising the VOX Threshold to about 35 or higher completely resolved the issue, and it was still plenty sensitive for my voice (though this probably depends on the microphone being used).? I'm pretty sure it was the internal mic triggering the vox - pressing an encoder button would always trigger it.

There was a change in??which prevented accidental VOX activation when pressing any buttons, by activating a timer that ignored microphone sounds for a short delay after button presses.?

I think it is a reasonable request to make, for the VOX to act only on the external microphone input, not the "noise canceled" version which takes input from the internal mic. So I will add that to my list.??
?
If you want to remove the internal mic, everything should work fine - Hans didn't need the internal mic signal for the noise removal, he just needed an A/D converter in the same group.

I'm not 100% sure this is correct, Stan. Having the internal mic in place may also feed in some noise from the power supply, to the ADC pin, which may be part of the noise cancellation. I am not sure that the noise cancellation will work the same way if the internal microphone is removed. So I suggest NOT doing that. For now, set the threshold higher so it does not activate too easily; and I will amend the firmware so that VOX acts on the raw input, not noise cancelled.??

73 Hans G0UPL
Re: CW Practice / Rag Chew

 

¿ªÔÆÌåÓý

Bonjour Benjamin,

Je me permets ce lien qui donne des explications assez claires et simples sur les param¨¨tres de propag

Au plaisir

73

-- 
Jean-Jacques - F5IJO
FISTS#17008 LICW#5902
Le 22/04/2025 ¨¤ 08:41, Benjamin ON5BGO via groups.io a ¨¦crit?:

GM Ed,
?
a Little off topic but could you point me some document about solar conditions on how to interpret this : Conditions were OK. SSN = 108, SFI = 156, A = 14, K = 5.
?
Many Thanks
73, Ben ON5BGO?
Re: CW Practice / Rag Chew

 

GM Ed,
?
a Little off topic but could you point me some document about solar conditions on how to interpret this : Conditions were OK. SSN = 108, SFI = 156, A = 14, K = 5.
?
Many Thanks
73, Ben ON5BGO?
Re: Release of version 1.2 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp) #ABS #ATU #PSU #QMXplus

 

Please add me too.
Re: QMX+ no power output, low SMPS bias current

 

I found that if I turn off the SWR Protection, it will report power in the diagnostics menu.? I then get the following values (into a 50 Ohm dummy load):

Band (m)
 Reported W
160
 5.1
80 2.5
60 9.9
40 1.5
30 7.4
20 1.4
17 3.5
15 1.2
12 3.5
10 1.3
6 1.3
I'm starting to suspect T507 might be the issue.? Tomorrow, I'll pull it and try rewinding it, then put it back.
Re: Newly assembled QMX, SWR=1.5 with dummy load

 

I agree.
Never use those dinky 50 ohm calibration references as a transmitter dummy load.
Unless your transmitter is sending out a max of a tenth Watt or so.
?
Hans has a nice 20W dummy load for $8.50,? perhaps include that with your next order.
https://qrp-labs.com/dummy.html
?
A cheap dummy load can be made with a bunch of 3 Watt metal film resistors in parallel,?
For example, four 200 ohm parts in parallel can deal with 5 Watts all day long, and cost about $0.25 each.
Mouser part number 603-RSF3WSJR-73-200R? is a good choice.
For 50 Watts, perhaps use twenty 1000 ohm 3 Watt resistors, Mouser 603-RSF3WSJT-52-1K.
?
If you already have a dummy load and want to use it as a 30 dB attenuator, you can do something like this:
?

in ---+--------R------+------- out to coax
? ? ? | ? ? ? ? ? ? ? |
? ? 50ohms? ? ? ? ? 50ohms
? ? ? |? ? ? ? ? ? ? ?|
? ? ?GND ? ? ? ? ? ? GND
?
The first 50 ohm resistor is your dummy load, it must be high power to deal with the transmitter.
R should be 1/2 Watt for a 30dB attenuator, can be 1/8 Watt for a 40dB attenuator, value of R calculated below.
The second 50 ohm resistor at the output can be 1/8 Watt.
I assume you are sending the sample out to something like a tinySA over coax.
The second 50 ohm resistor is the source termination to absorb any reflections coming back from the coax
There is a third 50 ohm resistor inside the tinySA that is in parallel with the second 50 ohm resistor,
together they make a load of 25 ohms.
For 30dB of attenuation we have a power ratio of 1000, so a voltage ratio of sqrt(1000)=31.62.
Those two parallel 50 ohm resistors in series with resistor R form a voltage divider.
To get a voltage ratio of 31.62, the value of R should be around (31.62 - 1) * 25 = 765.5 ohms for 30dB of attenuation.
For 40dB of attenuation, the value of R should be (sqrt(10000) - 1) * 25 = 2475 ohms.
Anything within 5% or so should be fine for our needs.
?
On the 30dB attenuator, having (765.5+25) ohms in parallel with the 50 ohm dummy load brings it down to? 47 ohms.
So in that case we might be better off with four 220 ohm resistors instead of 200 ohm resistors.
The transmitter now sees 55 ohms in parallel with 765.5+25, or 51.3 ohms, which is good enough for most of us.
If we then add a 2000 ohm resistor in parallel with that 51.3 ohms, we then have the transmitter seeing 50.02 ohms.
On the 40dB attenuator that additional parallel load of (2475+25) is so small it won't matter, so use four 200 ohm resistors.
At 40dB, you need to start being careful with how it's built to avoid unwanted coupling from input to output.
?
Check out that attenuator before using, as you don't want to burn out your tinySA.
I'd just hook the transmitter input port to a 12v battery, check for the a voltage of 12v/31.62 at the output
with a voltmeter.? Add that third 50 ohm resistor before measuring.
?
?
For US residents buying stuff direct from China:
In summary, the de-minimus exemption from tariffs for packages worth less than $800 expires on May 2,
at which point the minimum customs fee will be $100.? On June 2 it rises further to $200.
So you could be spending $210 for that $10 attenuator.
If you place an order now, it will probably arrive at US customs around May 2, so place your bets.
?
Jerry, KE7ER
?
?
On Mon, Apr 21, 2025 at 08:26 PM, Donald S Brant Jr wrote:

On Mon, Apr 21, 2025 at 05:04 PM, Wolfgang, DF1KZ wrote:
Are you shure that this dummy-load can withstand the output-power of the QMX (up to 5W!)?
It is also poor lab practice to use precision calibration kit standards as adapters or dummy loads.? They are precision instruments and should be given requisite care.??
10 watt 30dB attenuators are less than $20 on AMZN and likely stupidly cheap from China, they will work as a dummy load or attenuator.??
?
No ham station should be without a suitable dummy load, anyway, IMO.? Suitable meaning able to handle full output power for long enough to make meaningful measurements.
73, Don N2VGU
Re: Case for Drok Buck/Boost Converter

 

Search for "DIY Shell kit for XYH3606 DC buck boost converter". There's a ton of them out there.
Ron K0IDT
Re: QMX+ no power output, low SMPS bias current

 

And the bad transistors were labelled BS170.? It's probably my fault for going for the option with the quickest delivery on Amazon.
Re: QMX+ no power output, low SMPS bias current

 

The diagnostic screen is still consistently reporting 0.0W for every band when I press T, hence my turning to the Oscilloscope to get measurements.
Re: Newly assembled QMX, SWR=1.5 with dummy load

 

On Mon, Apr 21, 2025 at 05:04 PM, Wolfgang, DF1KZ wrote:
Are you shure that this dummy-load can withstand the output-power of the QMX (up to 5W!)?
It is also poor lab practice to use precision calibration kit standards as adapters or dummy loads.? They are precision instruments and should be given requisite care.??
10 watt 30dB attenuators are less than $20 on AMZN and likely stupidly cheap from China, they will work as a dummy load or attenuator.??
?
No ham station should be without a suitable dummy load, anyway, IMO.? Suitable meaning able to handle full output power for long enough to make meaningful measurements.
73, Don N2VGU
?
Case for Drok Buck/Boost Converter

 

Has anyone found a custom case for this buck/boost converter please? (Or models with the same dimension)
?
?
(I don't have a 3D printer)
?
Thanks
Re: QMX+ no power output, low SMPS bias current

 

Richard, I'm glad you found the BS170 problem.? They probably sent you the wrong type of transistor, since all BS170s in those type of packages have the same pinout.?
?
I think the peak-to-peak voltage measurements that you made on the bands with high power (over 6W) probably have some measurement problem, since I don't think those voltages are possible with this design.? If they are real measurements, something is definitely very wrong.
?
Please post the power numbers reported on the Diagnostic screen, so we can compare them to the ones you are computing from the Vpp measurements.
Stan
Re: QMX+ shutdown problem #qmx #QMXplus #shutdown

 

On Mon, Apr 21, 2025 at 09:59 AM, @Ludwig_DH8WN wrote:
I would use a sharp pencil type tip for the solder iron, set the temperature to 350¡ãC, put a bit flux on D109, a bit solder at the tip and touch one side of D109. After a few seconds I would try slightly to lift this side of D109 using tweezers. After this the same for the other side until D109 is free.
Nothing beats TWO irons, one in each hand, for removing such components.? Touch each end and lift it off.?
I have been evaluating two of the Pinecil irons (with the shorter tips) and am pretty impressed.? I am able to drop the tip temperature 30-50¡ãF and get the same results as my older Weller irons, which now are getting old and failure-prone.? Lower temperature bodes well for the longevity of the tips and helps avoid scorched flux.? The irons sleep when no motion is detected or when you long press the "-" button, another tip saver.? These behaviors are among many programmable parameters, I left most at default settings until I understand the extensive "Iron OS" documentation.
ST-D2 and ST-B4 seem to be the most useful tips thus far, on mostly smaller work.? Having the temperature sensor located right at the tip helps them punch above their weight when soldering e.g. copper alligator clips to AWG14 wire.? Quick and easy, no waiting on the iron to catch up.??
They have a power display and pop right up to 50+ watts when I contact the joint, the response is near instantaneous.? I have found that I do not need the little screw which clamps the tip, the internal spring holds well enough.
If these hold up I think I have found the solution to my aging soldering station problem.
?
73, Don N2VGU
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