开云体育

I think that you may be overthinking this; the natural way is for the windings to go from a hole in the board, through the centre of the core, back round the outside, through the centre until there are 10 passes through the centre, then the wire come out of the core and into the hole in the board on the other side.

To wind the core the other way you would have to go from the board and round the outside of the core before going back through the centre. If it was wound like this it would be obvious, there would be loose wire everywhere.

Both transformers have to be the same. so their outputs are in phase.

If you really think there's something wrong with the design then don't install it.? There's no support in software for it at present.? Fit a wire in place of the top single turn.? Then wind and fit T507 when people have demonstrated that it's correct.

Chris, G5CTH

On Sat, Aug 5, 2023 at 01:55 AM, Karl wrote:

Walt
And they will be different. The schematic may show that Hans reversed one coil to make the bridge work (or to make the PCB connections work) BUT without knowing for certain we may face a do over.

I'm not crazy enough to want a "do over" on this one!
Hans! What say ye?

73
Karl
KI4ZUQ

I think the simplest option to prevent "do overs" would be for Hans to provide a configuration option to reverse the reflectometer "forward" and "reverse" selection which would be simple to do in firmware.? Alternatively, he could check for which sample is larger than the other, and automatically choose that as the "forward" one.? That, however, would be problematical if, for example, the output was infinite SWR (e.g. open circuit) when slight differences in Schottky diodes etc could make the "reverse" output slightly bigger than the "forward".??
If the configuration option were chosen, it could be accomplished by connecting a dummy load, or a known well matched antenna, and doing a "setup reflectometer" action where the firmware would select the higher output sensor as "forward".
?
--
Peter Lee
G3SPL

hi

I think digi mode has a wider audio bandwith than SSB?

I changed USB to LSB from system config and listened to hams on 40m clearly?

even powerful Chinese SW AM stations on 7.200 - 7.500 kHz?

73

muhsin TA1MHS?

I'm better at software than hardware.? Still ... staring at schematics can be fun.

First I'll show my ignorance.? Does Q108 conduct when the PWM_5V pin is high?? Or low?? I think I understand that when Q106 conducts source-to-drain, Q112 turns off, thus turning Q108 off.? When Q106 is open source-to-drain, Q112 is biased on, turning Q108 on.? (And D104 is there to ensure Q108 turns off quickly??? That's a guess.)

I've seen some speculation that the pulse width modulation (PWM) signal might be the culprit, somehow too high (or low?) of duty-cycle, causing Q108 to stay switched on too much.? Let's assume Hans' software never does that, and there's no mechanical way to put constant high (or low?) signal on the PWM_5V pin.? Though I've also wondered about intermittent connections in those connectors JP101/102.

Get to the point, Rich ...

I see that Q106 gate is connected to the inter-board connectors, easy to get hit with static electricity.? That's where the pulse width modulation signal controls the whole buck converter circuit.

What if electrostatic damage caused Q106 to fail open?? Q112 gets biased on and stays on, so Q108 gets turned on continuously.? Input power (~ 12V) goes to the 5V output rail.? C107 fails from overvoltage, probably D108 Zener fails from overcurrent, and Q108 fails from overcurrent.? If the D106 Schottky is there for reverse-polarity protection, it's probably OK.? There may be damage on the main board for things connected to the 5V rail.

How close am I to being ignorant?

Hans, I enjoyed your writeup http://qrp-labs.com/qmx/smpsstep.html

Click left encoder once to switch to Digi mode, filter is wide open there (like 100-3000Hz or thereabout)

73
Andrew KI7FXL

As I understand, QMX runs a narrow CW filter by default. How to set the filter width for SSB?

I'll take if Dale changed his mind!

I did the exact same thing.? I sent to Jeff Moore who is a wizard at troubleshooting and repairing all things QRPlabs.? He told me it was not worth it.? The over voltage damaged several key components.? Lots of smoke.? Should have left it and sent it to him before I tried troubleshooting it myself and shorted out two pins.? See my chat labelled qmx will not power up.??

Dave,
I'm sure you're right about the voltage. But as I said, no issues here and I think the voltage regulators or p/s's can handle this voltage. Biggest issue is finals- no real problem with matched antenna system, but it does make for minimal room for error.?
--
73, Dan? NM3A

Nice to hear someone using it as intended.

I use one of mine as the final for a train wreck Atlas 210x.
IT had VFO "improvements" so it got a DDS VFO and digital
dial.? I wanted to QRP it and save the existing 100W power
amp for the other one I have.? So the amp was a good match
and the 210 had the needed LPF and TR switcing. End result
is a good 5 band QRP radio that does well on battery.

--
Allison
------------------
Post online only, please no email.

I strongly suggest LMR600, a good vise to support it so it doesn't flip over the QMX.

;-)

Seriously, Not!!
Any cable with quality connectors, RG316, RG58C/U, RG8X are all good.

I do SSB at 5W on 20M for sport!? ?So don't overthink the idea of low power?
being a handicap.? Just use a decent antenna, high enough.

--
Allison
------------------
Post online only, please no email.

I agree. We have "right handedness" of every coil done so far and we have Walt's link:

Here is the battery charger for that battery finishes charging at 14.6v I believe? Dave VE3KCL
Compatible AC-to-DC Charger Specifications
Input Voltage: 120VAC/220 VAC
Output Voltage: 14.6VDC
Current: 2A
Connector: ?DC Plug
Model Number:?

Rich,

I often eliminate the feedline by using an EFHW antenna or random wire antenna.? I use the K6ARK kits which build the balun right onto the BNC.? No feedline. When I do use coax (dipole or vertical), I keep the coax as short as possible, and use RG-316.? But I'll admit, I'm more often working SOTA than POTA, where lightweight gear is more necessary.?

73,
Walt - KK4DF

I would/do use RG-58A/U.? It has a solid polyethylene dielectric rather than foam, the center conductor is stranded, and it is cheaper than a lot of other options.? LRM-240 is big, has a foam dielectric, and solid center conductor.? RG-8X has foam dielectric.? Though RG-58A/U can't bend as tightly as RG-8X, I believe it will withstand more abuse due to the solid dielectric.? I may very well be wrong on that.??

At 30ft on 20m you would have something like .66dB loss with RG-58A/U.??

Joshua

George,

I am using 10W linear amp with my usdx design. Am very happy with it.?

Here is my take on 10W linear amp:



73

Barb WB2CBA

Rich,?
It is a 6 Ahr, 12 V Bioenno battery. Approximately 13 V when freshly charged, settles down to about 12.5 V for most of the time. Yes I know it is above specified, but I don't think that should affect the on board p/s's. It is mainly a risk for the finals.?

I realize that I may jinx things by saying so, but I have used this battery for many outings on my 4 QCXs and my other QMX with no problems ever. I pay a lot of attention to good antenna matching. I do also have a QDX, but power to that is totally different, so not comparable.?
--
73, Dan? NM3A