Re: Possible QMX/QDX PA Improvement Idea
Good point. I probably didn't run the sim long enough for that effect to show up.
Tony
AD0VC
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Good idea!
Though I'd think a DC bias at the gates of 0v would mean the 5v swing?
is now going from -2.5v to +2.5v, not enough to fully turn on the BS170's.
Perhaps that 2k should go to 2.5v when TX is true, and to 0v when TX is false.
Getting a bit more complicated.
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Could go to a solid 2.5v rail, except that Hans has found reason to keep the?
DC supply to the final on during receive.
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Jerry, KE7ER
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On Thu, Apr 3, 2025 at 05:53 AM, mux_folder2001 wrote:
It occurred to me that the Interface between the ACT08 drivers and the BS170 gates could be AC coupled. A quick simulation with 100nf and a 2k to ground on the gates shows no ill effects. The advantage is two-fold. First, a BS170 failure that puts 12V
on the gates is less likely to damage the ACT08 outputs. Second, any failure that leaves the ACT08 outputs high for a long time is less likely to fry the BS170s.?
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Just a thought.
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Re: Possible QMX/QDX PA Improvement Idea
Yes, probably so. Still, I might play with the idea a bit more. It's all part of the fun.
Tony
AD0VC
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Hi Tony
In my experience, practically there are undesirable effects including loss of bandwidth (meaning reduced power at higher frequencies), lower power output and lower efficiency. It's my opinion that AC coupling would cause more problems than it
would solve.?
73 Hans G0UPL
It occurred to me that the Interface between the ACT08 drivers and the BS170 gates could be AC coupled. A quick simulation with 100nf and a 2k to ground on the gates shows no ill effects. The advantage is two-fold. First, a BS170 failure that puts 12V
on the gates is less likely to damage the ACT08 outputs. Second, any failure that leaves the ACT08 outputs high for a long time is less likely to fry the BS170s.?
?
Just a thought.
?
Tony
AD0VC
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Re: SWR and PWR does not show lcd
Doesn't show on my pre-assembled unit, either. But since they haven't bothered to put out a QMX+ operating manual, I can't be sure it's supposed to show.?
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Hi Braden
The QMX+ has its own assembly manual. The operating manual is the same for QMX and QMX+, and any differences between them are identified where they occur.?
73 Hans G0UPL
I didn't even know that the clock settings could be preserved, or that there is a place for a cr2032 battery in my QMX+. I didn't see anything about it in the manual, but of course the Plus doesn't seem to have a manual that I could find.
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Re: Possible QMX/QDX PA Improvement Idea
Hi Tony
In my experience, practically there are undesirable effects including loss of bandwidth (meaning reduced power at higher frequencies), lower power output and lower efficiency. It's my opinion that AC coupling would cause more problems than it would solve.?
73 Hans G0UPL
It occurred to me that the Interface between the ACT08 drivers and the BS170 gates could be AC coupled. A quick simulation with 100nf and a 2k to ground on the gates shows no ill effects. The advantage is two-fold. First, a BS170 failure that puts 12V on the gates is less likely to damage the ACT08 outputs. Second, any failure that leaves the ACT08 outputs high for a long time is less likely to fry the BS170s.?
?
Just a thought.
?
Tony
AD0VC
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I didn't even know that the clock settings could be preserved, or that there is a place for a cr2032 battery in my QMX+. I didn't see anything about it in the manual, but of course the Plus doesn't seem to have a manual that I could find.
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Re: QMX+ Power Output Question
Thanks for your input Dave (and Jeff).? It's good to know my QMX+ is not too far out of line with others.? ?I am not losing any sleep over the lower output on the higher bands, I was mostly concerned about 10 meters.? I did try to more evenly space the windings on the toroids as Jeff suggested, but ended up with the same results, so I think I am done.? Now I am focused more on why WSJT-X refuses to run on one of my my Windows 11 computers.? ?It was working, and then just stopped.? Have uninstalled and reinstalled it with no joy. (No big deal, it runs fine on my other computers).
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Tnx and 73,
Jim (w8ykg)
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Re: Possible QMX/QDX PA Improvement Idea
Good idea!
Though I'd think a DC bias at the gates of 0v would mean the 5v swing?
is now going from -2.5v to +2.5v, not enough to fully turn on the BS170's.
Perhaps that 2k should go to 2.5v when TX is true, and to 0v when TX is false.
Getting a bit more complicated.
?
Could go to a solid 2.5v rail, except that Hans has found reason to keep the?
DC supply to the final on during receive.
?
Jerry, KE7ER
?
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On Thu, Apr 3, 2025 at 05:53 AM, mux_folder2001 wrote:
It occurred to me that the Interface between the ACT08 drivers and the BS170 gates could be AC coupled. A quick simulation with 100nf and a 2k to ground on the gates shows no ill effects. The advantage is two-fold. First, a BS170 failure that puts 12V on the gates is less likely to damage the ACT08 outputs. Second, any failure that leaves the ACT08 outputs high for a long time is less likely to fry the BS170s.?
?
Just a thought.
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Thanks for your encouragement Dave. ?I need to learn to remember the highs rather than pondering n the lows! I’m looking forward to trying to get up to speed n this hobby.
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Paul
G8MAD
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Hi Stan
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Thanks for your reply. It didn’t occur to me to recheck the battery voltage but it still shows 3.15V on my dvm. I reinserted it ensuring good contacts with the positive pins of the holder. I nervously checked the voltage on the solder to the left and right of the holder, which I assume supplies the power to the RTC, and that also gives 3.15V. Without the GPS antenna cable connected and the Real time clock setting set to QMX+ RTC I set the clock manually and it still powers up showing the time 00:00.
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The GPS Vbat/Vdd settings - I couldn’t see these in the menu system so are these configured via a terminal connection.
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Paul
GMAD
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Possible QMX/QDX PA Improvement Idea
It occurred to me that the Interface between the ACT08 drivers and the BS170 gates could be AC coupled. A quick simulation with 100nf and a 2k to ground on the gates shows no ill effects. The advantage is two-fold. First, a BS170 failure that puts 12V on the gates is less likely to damage the ACT08 outputs. Second, any failure that leaves the ACT08 outputs high for a long time is less likely to fry the BS170s.?
?
Just a thought.
?
Tony
AD0VC
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On Thu, Apr 3, 2025 at 01:25 AM, <ng433@...> wrote:
Any ideas where to start looking for the short?
Check all the elements connected to the VDD rail and all the places where the VDD rail goes. With some luck you will find a tiny solder whisker or a tiny part cut from an element during construction and shorting VDD now.
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VDD to GND is like .5 ohms
and
Lin_Reg_EN signal is stuck at .7 volts?
may point to a broken controller.
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73 Ludwig
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Re: QMX+ rev 3 freezes shortly after boot
On Thu, Apr 3, 2025 at 10:25 AM, Stan Dye wrote:
Maybe Ludwig has more ideas.
Not so much in the moment. Maybe I will do a test using a cheap evalboard containing a STM 32. I want to check what will happen in case of VDD = 4.5 V or so. Will it stop? Yes, if not it's no proof for the particular QMX+. But if it stops it would point to raising VDD first and stopping the STM32 after this and not vice verse.
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It is not likely a capacitor issue; their failure rate is very low. ?It is more likely a temperature issue, where something is thermally expanding just enough to cause a short, or a component is failing and shorting as it heats up, or a 'cold' solder joint is changing its connectivity.
This is also my favorite.
There is also a lower possibility for an unreliable solder joint for one or more IC pins.
And there is a lower possibility for failure inside an IC. Lets assume the TXCO or IC202 is stopping when heat a bit up. This would stop the controller and the SMPS couldn't work right.
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It would be nice to use an oscilloscope to check the clock signal before and after IC202 in "frozen" state.
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It maybe interesting to see what happens when TCXO and IC202 are cooled a bit or heat up a bit during work. Would the period until the controller stops be significant longer / shorter?
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73 Ludwig
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Re: Available Hand Mics for QMX SSB ?
Eric,
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I do not see an order page for the mic.
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Dean
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Re: Help with partially fried QMX
Stan - that was super helpful.? Thank you for taking the time to type that out for me/other hams that want to learn by doing (or by destroying).?
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After i read the earlier post about the pin to T507 i assembled enough non-panicky energy to actually go and look at the traces in the assembly manual.? Lo, what did I see?? Indeed a direct connection to T507.? I was operating at 7V for a 9V QMX, but indeed over extended period.
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The support of you, Steve, and others who have answered my questions over the years since my first QCX build gives us electronically-uneducated persons the readiness to venture forth and enjoy this world of home-finished qrp radios.
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It is all very appreciated. Thank you!
JD
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Re: QMX+ rev 3 freezes shortly after boot
On Thu, Apr 3, 2025 at 02:25 AM, Stan Dye wrote:
A question regarding this statement.? Did it freeze up before you cut the power??
And I'm confused about your jump from 0.8A to 0.2A.? You mean it was running at 0.8A nominally, then dropped to 0.2A when it froze up?? This seems wrong
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Hi Stan, apologies - you’re right. I mistyped when I said it jumped from 0.8A to 0.2A. The jump was from 0.08A to 0.2A, and it did freeze before I cut power.
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I’ll do another sweep of the boards for small shorts or solder blobs or cold solder joints as well. Thanks for your help!
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Re: QMX and power bank PD
The USB cable is a good option to be able to use any pd power bank and not need to make a custom battery with buck converters and other kit electronics.? Also one less thing in a bag.?
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Mine runs a little over 12v, 12.3 was the max it hit, so I would expect yours to perform around that.
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The variable pd cable is also viable, just change the voltage without the radio connected as it might change to the higher, 15v, option and that is no good.
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73
Jason
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Re: QMX and power bank PD
Did a search looking for this kind of assurance. I have a factory built QMX - I've not been able to use it yet - which I was able to power on using those cheap AA battery banks filled with Duracell batteries to make up the 12v.
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It's a nice little power solution, if a bit of an expensive way to go about it, even if you populate the power bank with rechargable AA batteries. So it was from there I went looking in to a power bank solution.
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Yesterday I purchased an Anker power bank and a 12v USB to DC PD cable (links below). Hopefully these should do the job safely and reliably. I also purchased one of those cheap little voltage testers just to see what power is going through to the QMX from the power bank. I'm not expecting anything super accurate, but hopefully a ballpark visual would be good (linked to it below).
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Voltage tester:
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Power Bank:
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USB Cable:
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Paul,?
Take heart! Most of the things I teach to younger (and some almost at my age, 80) I learned by mistakes, misunderstandings, and just trying this and trying that. Just the fact that you admitted how you had made the mistake shows you will be a good teacher. ?Good teachers can’t be proud because if you are proud you can’t confess your mistakes. ?Keep learning, keep on keeping on, and see one, screw up one, then teach one…. We are all brothers in this hobby.
My favorite simile of a good hobby is one that gives you a heart warming feeling, similar to John Wesleys “heart warming feeling” at Watersgate. ?Italian changes you and your response to the world. In this messed up world we need a hobby to help us cope and stay sane. ?Ham radio has done that for me for 65 years. ?
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On Apr 3, 2025, at 2:15?AM, Paul G8MAD via groups.io <paultostevin@...> wrote:
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Hi,
?
Although I got my licence over 40 years ago, I never pursued amateur radio as an interest until now. So, I was very excited this week to take delivery of my first HF rig - a new assembled QMX+. Even more excited, when connecting it to a homebrew efhw I could hear CW and see the decoded morse code (which I am currently learning).
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But all that excitement was marred by me being an idiot and not inserting the cr2032 battery for the RTC correctly. I assumed I just had to push it into the holder when I should have slid it in under the +ve connectors - so when the time was being lost on shutting down the rig I found that I had bent the +ve positive pins so they were in contact with the -ve terminal of the battery. I bent them back so when inserting the battery correctly they are now in contact with the +ve side of the battery but I lose the time every time I power down.?
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I have tried different configurations with the Real time clock parameter set to QMX+ RTC or software, manually setting the time or attaching the antenna for the internal GPS module and letting that set the time but with no success. So have I damaged the RTC components?
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Paul
G8MAD
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PS it was reading the posts in this group and all the support that it offers that made me decide to go for a QRP Labs radio. Thanks.
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Re: Available Hand Mics for QMX SSB ?
Karl, I cut the cable and soldered each wire to two other 3-wire cables. Each individual wire was insulated with tiny heat shrink tubing, and finally the entire cable at that place was insulated with two layers of heat shrink tubing.
The wires are thin and you need a steady hand, but it's doable.
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Zrinko Ivan, 9A7AM
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Braden Glett
Michael Shiplet
Jason
David Wilcox K8WPE