I think there's a bug in the "Configuration --> Digi interface --> TX shift thrshld" entry field.? It defaults to '500' (milliHertz), but no more than two digits (00-99) can be entered from the terminal or directly.

This is with firmware versions 006 and 009, at least.

73,

? Dan
? N7SHM

On Thu, Aug 24, 2023 at 01:46 AM, Rick Crowther wrote:

I meant only to rig up temporary linear supplies on my bench

hello Rick, Hello Hans,

this is exactly what I was aiming for myself: a temporary replacement of the smps boards until all other smoke tests have been succesfully passed.

Hans: really no offence intended! I am of an older school and do not trust these new-age gadgets piloted by software, not because of paranoia, but because of the fact that they do not belong to my trusted analog world. I find the ideas standing behind the SMPS concept of the QMX most refreshing and innovative: this is the main reason I am glad of having purchased a QMX, without having been in need of yet another qrp toy.

But now.. I am sort of discouraged by my own courage and would like to go one step behind into those quiet linear waters I am used to. Not for good, but at least for the first current intake of the fine rig. Afterwards, having thanks to Chris a test checklist for the SMPS boards outside the rig, without danger of damaging the main professor, I would maybe gain some courage and "replace the linear replacement" with it's new age microprofessor controlled switching PS.

This is what I meant. You might help by telling me if this is doable or if I am to expect some latch-up phenomena during power-up due to the fact that the 5V rail would come alive before the 3,3V would do. But latch-ups are not harmfull, so if you do not have an answer to this question, just forget it: I will find it out by myself.

Yours friendly, Razvan dl2arl?

I'd like to get the cdc_acm serial port on the QDX to work on ChomeOS in the Linux (Crostini) container. I'm looking for the Vendor IDs(VID) and Product IDs(PID) for all QRP Labs products so everyone can benefit, not just QDX owners.

On ChromeOS USB devices can be passed through to a Linux container. Currently the QDX works great on Crostini(Full OS container on ChromeOS) except the /dev/ttyACM* device from the cdc_acm driver is not passed through to the container. You can still use a terminal app from outside the container to manually send CAT commands and use VOX but there's no ability for WSJT-X or JS8Call to talk to the serial port.?

I'm opening a request to have these added to the list of devices allowed for pass through. They've done this for other cdc_acm devices when requested. I'm going to ask if all cdc_acm devices can be passed through but they may have a reason to stick with white listing by VID/PID.

I have the VID/PID for my QDX but I'm not sure if there are any other chips/IDs being used on other QRP Labs products and/or versions. If someone has a comprehensive list that would be great, but I'll take them individually here if people want to post them. I'll collect what I get over the next few days and submit a request to the Chromium bug tracker.?

Linux users can plug in their device and check the output of 'dmesg'. I'd be looking for a block of text like this:

[ 1410.951927] usb 1-1.1: new full-speed USB device number 8 using xhci_hcd

[ 1411.134168] usb 1-1.1: New USB device found, idVendor=0483, idProduct=a34c, bcdDevice= 1.00

[ 1411.134181] usb 1-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0

[ 1411.134185] usb 1-1.1: Product: QDX Transceiver

[ 1411.134188] usb 1-1.1: Manufacturer: QRP Labs

[ 1411.177327] cdc_acm 1-1.1:1.0: ttyACM1: USB ACM device

The diode is a good idea I think. Thisis based not only on simulation but on measurements I have made with my scope.

In my case, the loss of two or three sets of BS170 in my two QDX units led me to try different transistors. I ran the other transistors without any failures we for months. But I was curious why the BS170s would fail and the TN0106 and VN0606 would not. Yesterday I got a new scope that allows me to see transients and I decided to look at the QDX with VN0606 transistors in it. To my surprise, the glitch at the end of a transmission was over 120 volts measured at the center tap. The transistor drains were similar. The spike was 100ns wide at the 60 volt level. And this is into a dummy load. The transistors must just be capable of dealing with this.

I then replaced the transistors with BS170s and discovered another surprise. The spike was below 60 volts and had a broad flat (but ragged looking) top.?

Then I added the commutating diode and the spikes were gone.?

Right now my theory is that the BS170s are operating in a "make before break" mode which minimizes the di/dt. The VN0606 (and TN0106) might be in the "break before make" mode. The specific operating conditions might possibly allow the circuit to move between these two cases and the BS170s are just not capable of handling the over-voltage spike while the other transistors can. Just a theory mind you. I have not tried yet to make measurements to verify this. Prior to these measurements, I was thinking that the opposite would be the case, thus explaining why the VN0606/TN0106 did not fail.?

In any case, I am now running with BS170s again but with the diodes installed. We shall see how long this lasts.

Tony

AD0VC

---

From: [email protected] <[email protected]> on behalf of John Z <jdzbrozek@...>
Sent: Monday, August 7, 2023 6:14 AM
To: [email protected] <[email protected]>
Subject: Re: [QRPLabs] QDX Success story

?

Simulations are here:

/g/QRPLabs/message/105254

JZ

On Mon, Aug 7, 2023 at 8:07?AM John Zbrozek <jdzbrozek@...> wrote:
>
> Hi Pierre,
>
> The diode simply is in parallel with the 47uH inductor L14, with the
> orientation shown in the photo provided by Paul W9AC. Cathode towards
> the power supply connection, anode to the transformer center tap.
> Any of the diodes he mentioned? (1N4448, 1N4148, 1N914) will do a fine
> job of absorbing the end-of-transmission voltage spike it produces.
> I have used a 1N914.
>
> /g/QRPLabs/message/105256
>
> Here you can see simulations with and without the diode present.
>
> On another thread, Evan, Hans and I explore the ability of QDX to
> withstand SWR. It seems to have a reputation for SWR intolerance but I
> think there is a case that the problem may actually be as described
> above.
>
> /g/QRPLabs/message/106759
>
> Regards, JZ KJ4A
>
> On Mon, Aug 7, 2023 at 7:46?AM Pierre FK8IH <jb.gallauziaux@...> wrote:
> >
> > Could you please elaborate: what diode, how did you connect it? A handmade schematic and a photo would be nice.
> > 73
> > Pierre
> > FK8IH
> >

On Thu, Aug 24, 2023 at 01:46 AM, Rick Crowther wrote:

I meant only to rig up temporary linear supplies on my bench

hello Rick, Hello Hans,

this is exactly what I was aiming for myself: a temporary replacement of the smps boards until all other smoke tests have been succesfully passed.

Hans: really no offence intended! I am of an older school and do not trust these new-age gadgets piloted by software, not because of paranoia, but because of the fact that they do not belong to my trusted analog world. I find the ideas standing behind the SMPS concept of the QMX most refreshing and innovative: this is the main reason I am glad of having purchased a QMX, without having been in need of yet another qrp toy.

But now.. I am sort of discouraged by my own courage and would like to go one step behind into those quiet linear waters I am used to. Not for good, but at least for the first current intake of the fine rig. Afterwards, having thanks to Chris a test checklist for the SMPS boards outside the rig, without danger of damaging the main professor, I would maybe gain some courage and "replace the linear replacement" with it's new age microprofessor controlled switching PS.

This is what I meant. You might help by telling me if this is doable or if I am to expect some latch-up phenomena during power-up due to the fact that the 5V rail would come alive before the 3,3V would do. But latch-ups are not harmfull, so if you do not have an answer to this question, just forget it: I will find it out by myself.

Yours friendly, Razvan dl2arl?