Re: Best ways to measure output power w/ an o'scope and access ground
The DIY pad is unnecessary and very special resistors and construction are needed to stay linear and resistive at RF. ?It will give imprecise results at best and as described may also introduce SWR issues in the cable between it and the measuring device?
Hopefully your scope came with a good x10 probe (!). That is absolutely the best way to use a scope to sample RF voltage and on x10 a good one will not bother the main signal much or deliver too much voltage to the scope input . ?Scope probes /cables are specially constructed for exactly this purpose and to minimise SWR problems inside their own cable?
(If you want more than ‘fairly properly)
For greater precision and/or use with a spectrum analyser then using a 100W 50ohm through attenuator of 30 to 40dB is the way to go but the price of a good one is only for the very enthusiastic.)
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Re: Best ways to measure output power w/ an o'scope and access ground
Yes! ?Put a 39k resistor in parallel with that 10k and you have 50dB attenuation ?
FWIW I use that set up together with an AD 8307 style (set up for -60dBm to 0dBm) power meter. ?That 50dB attenuation then gives me 1mW to 100W. ?
That half watt rating would apply to the 10k resistor (for 100W measurement) by the way.
73
Rod
G0VKX
?
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Seems like a firmware bug, or at least undesired behavior - Intended behavior of "GPS protection" mode is to prevent the GPS from triggering CW transmissions, but it is also preventing CAT and beacon transmissions.
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Re: #qmx Antenna Tuner Can Kill PAs
#qmx
Just a thought.
?
Hows about creating an external high/low power switch in line with the DC cord ?
It could switch between say 7.5v and 12v (or what ever, using either a fixed voltage regulator(s)
or a single LM317 with a switched resistor as per the data sheet.
Requires no hacking of the rigs internals.
Do not do this. The QMX's CPU-driven power supply does not respond quickly to changes in input voltage. The issue is documented here: A firmware update has improved, but not totally fixed the issue. Myself and at least one other person have killed QMXes in this manner since that update.
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Re: Best ways to measure output power w/ an o'scope and access ground
To expand on the previous:
Your PA will see a 10k load in parallel with the 50 ohm dummy load. It won't even notice the extra VSWR.
The attenuator will have an output impedance of 50 ohms, so it will match just fine into your 50 ohm coax and 50 ohm oscilloscope termination resistance.
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I rather agree with you Jerry, the
hostility shown to you on this group is appalling. There's a lot
of people who should be ashamed of themselves.
From what Hans has said on previous
occasions some mail providers block the QRPLabs email as spam.? I
don't know if it's actually hidden somewhere if you look but some,
Gmail for example, simply delete messages they don't like with no
notice to anyone.
This isn't under Hans' control, he
can't go to your email provider and ask to be let through as he
isn't a spammer.? You may be able to adjust your settings,
whitelisting the QRPLabs email perhaps.
AIUI an email will have been sent
automatically when PayPal sent the money. Perhaps Hans has
contacted you privately.? The last one he responded on the group.?
When your order is shipped the shipper will also start
communicating.
As for the group, it's very busy but
hidden in the noise is some useful information. The difficulty is
separating the good information from the bad.? Starting with Hans'
messages would be a good start.
I've never had much success with the
search, it will find things but you need to know what you are
looking for.? I've found my own messages by searching for a word
that is in it and nowhere else.
Hope this helps,
Chris, G5CTH
On 11/09/2023 21:07, Jerry Moyer via
groups.io wrote:
toggle quoted message
Show quoted text
In my opinion, the impatient
people are the ones that are impatient about my one and only
single inquiry on the matter using the only means at my
disposal to do so.? Also there is no obvious way to ask
a question about tracking on the QRP Labs website other than
a link is provided for tracking information that does not
actually provide any tracking information.? I'm not
impatient that I haven't received the order.? What I'm
impatient about is that I haven't received tracking
information for my week-old order.? Also, considering the
ridiculous amount of spam I receive to my email spam folder
daily, many times from the same sender over and over again,
it seems odd to me that anyone would be blocked from sending
me an email.? In fact it seems odd enough to me that it
should be a problem that can be fixed, but it can't be fixed
unless the shipper knows about the problem. Hence my email
response.? ?
Very Patiently waiting,
Jerry AC5JM
On Monday, September 11, 2023 at 12:28:05 PM CDT, Gary
Bernard via groups.io <garybernard2@...>
wrote:
Same old questions about order status
and delivery over and over again. I guess people
think they are buying from Amazon. Well. they're
not.
?I think Hans should put up a
description of his small company and small staff.
Put it up on his site in giant letters in living
colour.
These so common and daily questions
simply take up unnecessary space. Patience is
apparently not a virtue amongst the ham population.
Leave Hans alone to continue do his
magic. He has made more contributions to ham radio
then any of the big three, and guess what, they're
affordable.
Rant over.
73, Gary W0CKI
On Monday, September 11, 2023 at 11:04:36 AM
MDT, Jerry Moyer via groups.io
<ac5jm@...> wrote:
77424 is my order. No email when it shipped
or if it shipped. ?It’s been almost 1 week.
?When should I bother you about it again? ?It
would be nice if there was a way that I could
get some sort of status or tracking number but
I guess that’s impossible??
Thanks,
Jerry AC5JM?
?
Hello John
There is an issue with some email
providers blocking QRP Labs shop
email as spam. This is probably why
you didn't get an email.
Confirmation emails are sent
automatically as soon as your
payment comes in from PayPal/Credit
card. Only manually by me if it's a
bank transfer. I see your order
ID?77490 so all is well. Just a
matter of spam blocking problems.
When it ships you'll also get a
FedEx email which probably?won't get
blocked.?
On
Mon, Sep 11, 2023 at 7:11?AM John R
< xp100u@...>
wrote:
Hello everyone,?
I placed an order thru PayPal
as a guest last week, so how
long does it normally take to
get an order confirmation? I am
well aware that it will be some
time before my QMX ships, I just
want to be sure I'm in the order
queue?
?Thank you,
John
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Re: Best ways to measure output power w/ an o'scope and access ground
According to the datasheet your oscilloscope is rated for up to 400 volts peak, or 800 volts peak-to-peak. The limiting factor will be the oscilloscope's ability to attenuate the signal into its actual measurement range, but you're certainly not going to break it. The limiting factor will be whether the oscilloscope has a measurement range that will fit the full waveform. My own cheap oscilloscope is rated for 300 VRMS, but can only display a signal up to 80 volts peak to peak.
I think in your case what I would do is build yourself an attenuator with an L-pad in it, 10k ohms in series and 50 ohms in parallel, and hook it up to a T just in front of the dummy load. Turn on the 50 ohm terminator in your oscilloscope input (rated for up to 0.5 watt) and blammo. You can now safely measure up to 100 watts.
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Just did factory reset, and its working!!!
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Re: QMX pre-flight check - incipient Q103 / Q104 short in buck regulator
I'll bow to your experience. In my case, I don't think the short
would have been fixed by moving Q103--There was a genuine solder
bridge that I could see, independent of Q103's position!
This was my first venture in trying to adjust SMT stuff, so I'm
choosing to chalk it up to experience! ;-)
73, Paul -- AI7JR
On 9/11/23 21:11, Hans Summers wrote:
toggle quoted message
Show quoted text
Hi Paul
Moving Q103 always works. It always clears the
short. I've done upward of a hundred. It always works
afterward.?
However we have to accept that it's a delicate
operation and not everyone will be successful at it, the first
time.?
I'm just saying that in principle it does work
if done correctly. There's about a 1mm gap between the drain
pads. Once the short is cleared there's no further need for
action. In all the ones I've seen there's also no marginal
situations. The bridge is either clearly there, across the 1mm
gap, or it isn't.
Apparently, moving Q103 works for some people and not for
others... I actually had a solder bridge, in addition to
the positioning of Q103 over the pad for Q104. In my case,
I used an air gun to lift Q103 and then I resoldered it
into the correct position.
Unfortunately, I accidentally also removed a resistor and
diode but didn't notice. Repairing that, I left a stray
clipped lead that shorted and killed the MCU.
Lesson learned: Don't get so focused on what you're doing
that you lose awareness of unanticipated events! :-(
New QMX on order.? :-\
Paul -- AI7JR
On 9/11/23 13:15, Kees T wrote:
Here is a picture of Q103 moved over just a little.
Definitely no short to the Tab now and it was easy to do.?
Just remember to get the Tab hot enough to melt the solder
before exerting pressure.
73 Kees K5BCQ
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Re: QMX Board pinout vs schematic and PSU voltages
Hans,
At one time I too thought that it was the current that mattered because I believed latchup was the issue.?
Later I understood that view to be wrong.?
The spec is clear in that it speaks to a voltage vulnerability, not an injected current issue. It is the oxide underneath the P and N MOSFET gates at the input receiver that is subject to breakdown and failure when the input voltage is 4 volts or greater above Vdd.?
The time of greatest vulnerability in this circuit is in startup when +12V has risen, LIN_REG_EN is rising fast, and Vdd has not yet risen. The port is not yet configured at that time, but the receiver gates are very much connected to the input pin and to LIN_REG_EN.
The receiver circuit is not yet getting the protection benefit of the internal ESD block, as Vdd is not yet up, still at or near zero. The input is not 5V tolerant at that moment.?
The V(absmax) at that time then is Vdd + 4. Four volts. That's it. That is the message of section 6.3 of the AN. The "black box warning" of circuit damage follows.
JZ
Hi John
Note that in STM32 all pins are configured as inputs at power-up by default until you change something.?
At such time as the code changes the GPIO pin to an output, it will certainly have no trouble sinking those few microamps.
Simon, Kees,
For those of us who do not like plowing through datasheets, STM's application note AN4899 could be the short-cut to understanding what happened. See section 6.30 (Voltage protection when no Vdd is supplied.) That is the condition obtained when +12V pops up but the linear regulator has not yet charged its output network. The port is in an undefined configuration at that time as the MCU has not yet come out of reset.
That AN also might clear up some misconceptions I spotted on this thread about how that port should work. It is not a 5V tolerant port, for example, as that only applies to ports configured as inputs, not as outputs.
JZ Simon,
A short between VDD and Ground is not a good sign. One individual commented that he found a short between SMPS connector pin #4 and Ground and cleared it.?
It could be a bad capacitor or a bad VDD pin on an IC (including the processor).?
73 Kees K5BCQ
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Re: QMX pre-flight check - incipient Q103 / Q104 short in buck regulator
Hi Paul
Moving Q103 always works. It always clears the short. I've done upward of a hundred. It always works afterward.?
However we have to accept that it's a delicate operation and not everyone will be successful at it, the first time.?
I'm just saying that in principle it does work if done correctly. There's about a 1mm gap between the drain pads. Once the short is cleared there's no further need for action. In all the ones I've seen there's also no marginal situations. The bridge is either clearly there, across the 1mm gap, or it isn't.
Apparently, moving Q103 works for some people and not for
others... I actually had a solder bridge, in addition to the
positioning of Q103 over the pad for Q104. In my case, I used an
air gun to lift Q103 and then I resoldered it into the correct
position.
Unfortunately, I accidentally also removed a resistor and diode
but didn't notice. Repairing that, I left a stray clipped lead
that shorted and killed the MCU.
Lesson learned: Don't get so focused on what you're doing that
you lose awareness of unanticipated events! :-(
New QMX on order.? :-\
Paul -- AI7JR
On 9/11/23 13:15, Kees T wrote:
Here is a picture of Q103 moved over just a little. Definitely no
short to the Tab now and it was easy to do.?
Just remember to get the Tab hot enough to melt the solder before
exerting pressure.
73 Kees K5BCQ
|
Re: QMX Board pinout vs schematic and PSU voltages
Hi John
Note that in STM32 all pins are configured as inputs at power-up by default until you change something.?
At such time as the code changes the GPIO pin to an output, it will certainly have no trouble sinking those few microamps.
Simon, Kees,
For those of us who do not like plowing through datasheets, STM's application note AN4899 could be the short-cut to understanding what happened. See section 6.30 (Voltage protection when no Vdd is supplied.) That is the condition obtained when +12V pops up but the linear regulator has not yet charged its output network. The port is in an undefined configuration at that time as the MCU has not yet come out of reset.
That AN also might clear up some misconceptions I spotted on this thread about how that port should work. It is not a 5V tolerant port, for example, as that only applies to ports configured as inputs, not as outputs.
JZ Simon,
A short between VDD and Ground is not a good sign. One individual commented that he found a short between SMPS connector pin #4 and Ground and cleared it.?
It could be a bad capacitor or a bad VDD pin on an IC (including the processor).?
73 Kees K5BCQ
|
Try adjusting the LCD brightness, turn it all
the way counter clockwise.? I made same mistake when I first
turned mine on.
Good luck? 73
Emory? WM3M
On 9/11/2023 11:36 PM, Nurlan wrote:
toggle quoted message
Show quoted text
Does this mean that the firmware was installed successfully? I
hear radio noise in my headphones. The volume is adjustable. When
I press the left encoder, the radio turns off.
What could be the cause of the malfunction?
|
Does this mean that the firmware was installed successfully? I hear radio noise in my headphones. The volume is adjustable. When I press the left encoder, the radio turns off.
What could be the cause of the malfunction?
|
Re: QMX Board pinout vs schematic and PSU voltages
Typo ...that should be section 6.3
On Mon, Sep 11, 2023, 9:01 PM John Zbrozek < jdzbrozek@...> wrote: Simon, Kees,
For those of us who do not like plowing through datasheets, STM's application note AN4899 could be the short-cut to understanding what happened. See section 6.30 (Voltage protection when no Vdd is supplied.) That is the condition obtained when +12V pops up but the linear regulator has not yet charged its output network. The port is in an undefined configuration at that time as the MCU has not yet come out of reset.
That AN also might clear up some misconceptions I spotted on this thread about how that port should work. It is not a 5V tolerant port, for example, as that only applies to ports configured as inputs, not as outputs.
JZ Simon,
A short between VDD and Ground is not a good sign. One individual commented that he found a short between SMPS connector pin #4 and Ground and cleared it.?
It could be a bad capacitor or a bad VDD pin on an IC (including the processor).?
73 Kees K5BCQ
|
Re: QMX pre-flight check - incipient Q103 / Q104 short in buck regulator
Apparently, moving Q103 works for some people and not for
others... I actually had a solder bridge, in addition to the
positioning of Q103 over the pad for Q104. In my case, I used an
air gun to lift Q103 and then I resoldered it into the correct
position.
Unfortunately, I accidentally also removed a resistor and diode
but didn't notice. Repairing that, I left a stray clipped lead
that shorted and killed the MCU.
Lesson learned: Don't get so focused on what you're doing that
you lose awareness of unanticipated events! :-(
New QMX on order.? :-\
Paul -- AI7JR
On 9/11/23 13:15, Kees T wrote:
toggle quoted message
Show quoted text
Here is a picture of Q103 moved over just a little. Definitely no
short to the Tab now and it was easy to do.?
Just remember to get the Tab hot enough to melt the solder before
exerting pressure.
73 Kees K5BCQ
|
Re: QMX Board pinout vs schematic and PSU voltages
Simon, Kees,
For those of us who do not like plowing through datasheets, STM's application note AN4899 could be the short-cut to understanding what happened. See section 6.30 (Voltage protection when no Vdd is supplied.) That is the condition obtained when +12V pops up but the linear regulator has not yet charged its output network. The port is in an undefined configuration at that time as the MCU has not yet come out of reset.
That AN also might clear up some misconceptions I spotted on this thread about how that port should work. It is not a 5V tolerant port, for example, as that only applies to ports configured as inputs, not as outputs.
JZ
Simon,
A short between VDD and Ground is not a good sign. One individual commented that he found a short between SMPS connector pin #4 and Ground and cleared it.?
It could be a bad capacitor or a bad VDD pin on an IC (including the processor).?
73 Kees K5BCQ
|
Mike--
Jeff Moore is one of several people here who often repair stuff
for others. He just looked at my QMX to see if I'd missed
something, and unfortunately we both agreed that my MCU got fried
somehow. :-(
But before you resort to that, listen in on some of the help
others have gotten and see if something applies to you. If you're
not technical or don't have the equipment, then people like Jeff
may be your best bet.
Good Luck!
73, Paul -- AI7JR
On 9/10/23 05:44, M0MDS Mike wrote:
toggle quoted message
Show quoted text
?
Hi,
?
I just
built the QMX but I can’t get it to power up so I can load
the firmware.
?
I
followed all the instructions as far as I can tell.
Can
anyone suggest a path where I can get it fixed.
?
Mike
?
?
?
?
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Re: QMX Board pinout vs schematic and PSU voltages
Simon,
A short between VDD and Ground is not a good sign. One individual commented that he found a short between SMPS connector pin #4 and Ground and cleared it.?
It could be a bad capacitor or a bad VDD pin on an IC (including the processor).?
73 Kees K5BCQ
|
Re: QMX pre-flight check - incipient Q103 / Q104 short in buck regulator
The only other thing I did was reheat the Source and Gate pins on Q103 to relieve any built up stresses from twisting the part a little. I don't think any pad insulation is required.
73 Kees K5BCQ
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Bruce Akhurst
Nurlan
Paul - AI7JR