Fascinating discussion.
Thanks!

73, Jerry, AC5JM

Could you repost the RWTST graphic.? I have low 10m power on my QDX.

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WSPR is a Weak Signal Propagation Reporter system, someone needs to be on the other end to RX. To get the most out of using WSPR one needs to REDUCE the TX power to somewhere between 9mW and 200 mW in order to gain any meaningful data that will translate into a modes potential (at that moment in time) I usually run 100-200mW when I setup for a session of QRP/CW. ?I have found that for the most part what I saw on WSPR is representative of the results that I will have but is of course dependent upon someone on the other end willing to participate.

Good evening all.? ?
? ? ? ?On my qcx+ build which went well this time, I have an audio issue that I'm trying to debunk.? Everything seems to be working as it should - about 4.97 watts in the dummy load- no smoke .? ? But when I key down I get the noise I'm hearing sounds like a blown speaker.? ?It doesn't matter which speaker or headphones I have attached to it.? ?I thinking that there's an problem in the audio part.? ??
? ? ?I'm definitely a rookie when it comes to electronics, but I can hold my own.? ?Any questions or suggestions? on where I should start to look at would be helpful .
? ? ?Thanks

Are you sure you downloaded the correct firmware?? There are versions for a single-band QDX.? Try an older version and see if that helps.

Correct multiband QDX is here:


Single band is here:


I did note that the latest single band is 1_08, and the screenshot you posted lists 1_10, so it's not likely.? Try the prior release:


73
Evan
AC9TU


73
Evan
AC9TU

I am sorry, the included picture is barely readable.
Here is an attachment with the image file

I would suggest a factory reset.? ?It looks like the EEPROM got messed up.


Look in the operating manual:


73
Evan
AC9TU

On Sun, Sep 3, 2023 at 02:16 PM, Hans Summers wrote:

Hi all

?

I agree a series resistor would prevent the GPIO conflict. The GPIO pin is necessarily configured as push-pull. A series resistor would reduce the efficiency of the buck converter. However my feeling is that if the resistor was small, say 220 ohms, it would suffice to resolve the fight and not significantly impact the efficiency.?

?

Gunnar, I'd like to understand why you're so sure the current through the zener and base-emitter is low? I agree as soon as the voltage rises it will stop the PWM and thus further energy being delivered into the inductor. My point is by this time significant additional energy was already delivered into the inductor which at 330uH, isn't tiny. Before the voltage rise could be detected and switch off the PWM. The energy will be dissipated through the zener and base-emitter. So my question is how are we so sure that it is "quite low", not a current spike which can kill the base-emitter junction? I'm just nervous because in my experience dumping even small energy into transistors via the base, was a quick death...

?

73 Hans G0UPL

Well Hans,
I made an LTSpice model and the simulation shows that the proposed solution will work.
The voltage step 6 to 12 Volt occurs at 30 milliseconds with zero risetime

With the selected zener, the voltage transient is limited to 5.5Volt without much drama.
At 30.6 milliseconds the overvoltage protection goes into analog regulation, but this mode will terminate as soon as the processor has adjusted the PWM duty cyclle so that Vcc is back to 5V
The current through D4 peaks 6mA@..., which will not kill the NPN transistor...
The PWM frequency is 166kHz and I adjusted the dutycycle manually to obtain 5V
I know that the components are not exactly the ones you are using, but this is not significant to show the principle

I will be happy to send you the model if you are interested

73 de SM5EIE /Gunnar

?

?

Still looking for what would make the QDX lose 20,30,40,60M. I am sure I did something to the board or a component but I can't figure out which.?

I've been poking around the board for a few days. Haven't made any progress. I see some documentation about jumpering things for different bands but nothing relevant to making it 80M only.

Anyone know what short/open/damaged component/trace causes this behavior? 60,40,30,20M should also be in this menu.?

I meant sma of course, I've not see a method too edit sent text to update it.

I finished building my QMX kit today.? On initial power, it started correctly in the bootloader mode.? I could load version 1_00_009, restart, and hear audio blasting out of my headphones (a good thing I did not have it on my ears).? I tried to lower the volume, but the QMX would not reduce the volume.

I pulled apart the control board from the main board.? I thought I might have an open connection on the encoder.? I did a visual inspection, and it looked like the common point for the encoder contacts was not connected.? I used a cut lead from another component to bridge the gap from the board to the ground pin for the encoder contacts side (not the push switch).

Put it back together, and now it will not start.? If I hold in the on/off encoder switch, my power supply registers 2ma as long as I hold in the encoder.? There is no backlight, so I assume that the processor is history.

I did pull apart the boards several times.? I did a visual inspection with a microscope.? Check the operation of the control board using an ohm meter.? The next step would be to do the buck converter tests.? I have little hope for the kit.??

The only thing I can think might have killed the QDX is how I turned off the QDX before I took it apart.? I pressed the power switch on my linear supply rather than removing the power plug.? There may be a surge on powering down that the buck converter could not handle and wiped the processor.

I will set it aside for now and let my head clear.

73
Evan
AC9TU

On Thu, Aug 31, 2023 at 08:23 AM, Ted 2E0THH wrote:

The finals don't need any protection.

You are incorrect. Even a perfect antenna is subject to random events such as antennas falling down or coax faults.?

A couple of diodes are cheap insurance for unforseen high-VSWR situations.

--- Zach
N0ZGO

Adam,

You are close.? It would work if the Digi filter goes below your sidetone.? I do not know for sure the cutoff of the QMX digital mode filter.? I believe it goes to 300Hz, so your scenario should work.

I finished building my QMX today and have run into problems.? I believe I have fried the processor, so I can not verify using a QMX, and the QDX does not have audio other than through the computer.

I suggest that you try it and see what happens.

73
Evan
AC9TU

On Sun, Sep 3, 2023 at 03:10 PM, DL2ARL wrote:

so at least for the time being, I will inhibit the "handover procedure" from the linear to the 3,3V buck converter

Could this be a software/firmware option?
73, Don N2VGU

On Sun, Sep 3, 2023 at 02:47 PM, Guido PE1NNZ wrote:

with L101=1.5R at 12V there is a theoretical peak current of more than 4A (12-5.6)/1.5, peaking to more than 25W 4*(12-5.6), so 5W might not be sufficient.

1N5368B (47V, 5W) states max surge current 2.7A????

Another concern when considering paralleling ever-larger devices is going to be the extra capacitance of those larger diodes across the RF output, especially in the higher bands.??

73, Don N2VGU

On Fri, Aug 11, 2023 at 05:38 AM, Shirley Dulcey KE1L wrote:

Cell phone chargers are often in the category of only delivering 5V or 9V

Most gentle Ladies and Gentlemen,

I humbly think that the PowerSupply Railway-Exchange we are all driving trough is for one reason unnecessarily complicated. I try never to raise oppinion against something if I do not have a better alternative. But in this case, I do. It is not my idea: I read about it in:

CQ March 2015
QRP Special
Page 18:?Behold Rockmitey, de ED Cobb?K4YFR es Ray Kauffman?AJ4YN.

Look what happens. Basically we need 5V to operate the radio (disclaimer: most of our qrp radios). In some cases we also need 3,3V, but that set apart, let us stick with the magic 5V level: because of USB and Cell-Phones 5V has become the standard of our age.

What we do in most cases is so wrong, in so many ways:

we probably start with the voltage of a single 3,7V LiPo Cell built in some Power Bank. The built-in converter (most probably of a some noisy, very bad efficiency) boosts this voltage to 5V. Than we use maybe another internal Boost-UP-Converter, maybe an external one to increase 5V to the 12V expected at the input of the (qrp) transceiver.

We feed the 12V into the rig of our choice, where, for the most of the time it gets down-converted to 5V (and probably to 3,3V too) with another efficiency loss. The 12V is only needed for the short TX Phase. I do not know what your mileage is, but for me, I am an SWL, most of the time, probably 90% of the time I spend on the HAM bands. I listen most of the time and transmit just now and then.

So why travelling trough this complicated UP-and-DOWN Railway-Exchange anyhow? What do I do instead?

Following the learning done in that CQ Magazine quoted above, I have modified some of my MTR-Transceivers (superb KD1JV designs) for the following path:

I start with 2 LiPo cells, yielding together 7,4V. This choice has another advantage: for a reason I do not know, it is much easyer to find a solution to charge a 2Cell LiPo battery than it is for a 3C or even worse for a 4C battery. A 2C pack not only can it be easily charged, but it also gets well balanced.

This 7,4 V supply is in MOST Cases enough for the MTR to offer a HF output at the qrp-qrpp border. In most cases enough for me. For the eventuality I would try to go up to "full legal qrp power", I use a Boost-Up converter to 11..12V that is only active during the TX phase. The transition could be made automatic (like described in the CQ article), driven by some PTT Level in the rig, but because I do not use this option often, it remains for me a manual switch.?

For the rest, using a LDO, I convert the 7,4V to 5V and feed the Rx Part of the MTR bypassing it's internal converter, whatever of a sort this one might be. Because of the relative low current consumption of the Receiver in the MTR, the conversion loss is minimal and not to be taken into account. The MTR5 even has an internal buck converter for this purpose.

Whatever I did, whatever I do suits best my needs. But in order to be able to do so, I had to modify the existing rigs to fit my needs. It would have been much easyer and straight forward if they would have been designed for a wiser and more modern Supply Voltage Railroad-Exchange. The QMX is a huge step ahead, but not in this direction. And because of it's adventurous behaviour, I will probably not feel at ease with it, so at least for the time being, I will inhibit the "handover procedure" from the linear to the 3,3V buck converter and at least feel safe, in the event I will not be.

If we like it or not (I do not!), we live in a USB dominated world, we must use LiPo cells and both of them are very badly suited for our old habitual 12V, voltage probably coming from the stone-age of electric development related to those lead-acid batteries formerly used in gasoline eating cars ...

just thinking loud.

yours friendly, Razvan dl2arl

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I have measured Doppler Shift on WWV due to a moving ionosphere, both when it is transitioning from day to night and vice versa, and to a lesser extent due to gravity waves in the ionosphere. ?It is on the order of tens of milli-hertz. ?So not really obvious to the casual observer, but really cool to this FMT nut.

On Tue, Aug 29, 2023 at 11:44 AM, Matt - HB9HWI wrote:

In CW Mode (actually what I want to use the QMX for):

Audio issues:

• Sidetone volume can’t be adjusted. It’s either rather quiet, very loud or changes with the AF volume.
• AF volume can’t be turned down to zero. I can always hear a strong station.
• Missing AGC is really an issue and I currently refrain from using the QMX for CW for that reason.

Like you, I have not been able to adjust the sidetone volume. I find it changes with the AF volume. Does anyone know if AGC will be coming in a firmware update?

Apart from that, my QMX seems to be working fine. I have been having fun with the terminal and looking at the sweeps. Thank you again Hans for a great kit.
? ? ? ? ? ? ? ? 73 de OE6FEG/M0FEU
? ? ? ? ? ? ? ? ? ? ? ? ?Matt