Re: Non-Resonant antenna for QMX POTA operations
Could you post a sketch of your antenna?? Thanks? Dan
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An addition that I should have included in the prior post:
In my estimation, simulation is good to help work out issues with a design.? Actual measuring should be done for an individual radio.? If you rely on measurements only, you can get into a parts variation problem.? Is your measurement sample large enough to verify the outliers in a production run?
The above is from experience in taking processes from R&D to production.? The results are not always as expected.? This is from food industry experience, but I believe the concept applies.
73
Evan
AC9TU
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Re: QMX Display Brightness
Mike, I'm glad to have learned that I can adjust overall brightness by changing values of R306. If I want to adjust this in the future, I now have some values to try. 73
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Willie and John,
I believe that the simulation works for the QDX version of the amp.? I'm unsure about the EER/power addition of the QMX.? That may be more of an issue when Hans offers the SSB upgrade for the QMX.?
Zener protection has been put on CW and Digital mode radios.? I have not seen it for SSB, though that does not mean it is not a common practice.? I do not have an extensive history with higher-power SSB construction.? Most have been at QRP? or under 20 watt levels.
Regardless, actual measuring is always better for an individual rig.
73
Evan
AC9TU
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Re: #qmx Battery voltage indicator does not follow automaticaly voltage changes
#qmx
Mine had the same behavior, the whole time I was running off of 4S LiFePO4, with Batt Full set to 13.200 and Step set to 0.233. Ever since I switched to 3S Li-Ion, with Batt Full set to 12.600 and Step set to 0.550, the battery indicator works as expected. Maybe this bug has something to do with the battery Red/Green threshold on 12.5V in the diagnostics menu.
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Hans!
I am 20+ years your senior. It should be me grumbling with skepticism
about your simulations and not vice versa!
:-)
Smiling anyway, JZ
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On Fri, Aug 25, 2023 at 11:59?AM Hans Summers <hans.summers@...> wrote:
Hi Willie
And, of course, the third question is if adding the commutating diode and/or the zemers will affect the output characteristics (spectral purity, spurs, harmonics), in such a way as to render transceiver illegal to operate.
Yes, spot on. That, and whether the diode and/or zeners add anything to the receive noise floor. Probably not. But I need to measure, simulation isn't good enough for me :-D
I tried to order some 47V zeners but got BZY47. Which is 9.1V. Sent back, and got BZY47 **again**. I should put in a large Digikey order in the next couple of weeks and will add some to it. Here Digikey orders take 10 days and incur a significant expense so you can't do it for a sub $1 order like you can in US.
73 Hans G0UPL
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#qmx Battery voltage indicator does not follow automaticaly voltage changes
#qmx
Hi all,
this is not really a problem, but? ....
The battery indictaor does not show a value after the QMX is started - it is "empty".
First, when I press the left? and then the right pushbutton, the indicator is "filled".
When I change the supply voltage during the QMX is running, the indicator only? shows updated values if the procedure I described above has performed.
73 Frank
?
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That's awesome, Karl! Great job! :D Yes, you could shift things around to try to move some of the peaks down, but the numbers as is, are certainly good enough to put into use right now, so you can enjoy your QMX this weekend, a well deserved reward! I'm glad the supplies I sent got you up and running. Mischievous little capacitive flea :P
73 Rick NF6G
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And, of course, the third question is if adding the commutating diode and/or the zemers will affect the output characteristics (spectral purity, spurs, harmonics), in such a way as to render transceiver illegal to operate.
Yes, spot on. That, and whether the diode and/or zeners add anything to the receive noise floor. Probably not.? But I need to measure, simulation isn't good enough for me :-D??
I tried to order some 47V zeners but got BZY47. Which is 9.1V. Sent back, and got BZY47 **again**. I should put in a large Digikey order in the next couple of weeks and will add some to it. Here Digikey orders take 10 days and incur a significant expense so you can't do it for a sub $1 order like you can in US.?
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Karl,
I would call these good.? There are only 2 windings on L12.? Both are used on 80, 60, 40, and 30 meters.? The first winding is used for only 20 meters.? The capacitor selection makes the difference between the other bands and 30 meters.
With the above understanding, changes to the 20 meter winding will impact all bands.? Looking across the sweeps, they are close to centered now, and the level is good.? You could make it worse rather than better.
Note,
The LPFs do not affect the receive function unless there is a fault.? They are much higher than the BPF upper limit.? You tweak the LPF toroids to get the best power out.
73
Evan
AC9TU
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Willie,
Simulation FFT says that the commutating diode does no damage to
spectral purity.
This makes sense for two reasons:
1) The current flowing through the diode is small and capacitive until
commutation takes place at the end of a transmission. That is where a
large diode current will flow, but only briefly.
2) The diode current never flows through the primary or the secondary
of the output transformer, and so it never makes it to the LPF.
If you are greatly concerned about spectral purity, consider that
sloppy winding of the output transformer, or parameter imbalances
between the two banks of PA transistors, will do more damage to second
harmonic cancellation and content than the diode can ever do.
JZ KJ4A
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On Fri, Aug 25, 2023 at 10:53?AM William Smith <w_smith@...> wrote:
And, of course, the third question is if adding the commutating diode and/or the zemers will affect the output characteristics (spectral purity, spurs, harmonics), in such a way as to render transceiver illegal to operate.
73, Willie N1JBJ
On Aug 25, 2023, at 10:38 AM, John Z <jdzbrozek@...> wrote:
?
Dan,
The QMX has a PMOSFET modulator that can gracefully ramp down the supply voltage to the power amplifier stage, under digital/MCU control. That circuitry is essential for the QMX wave shaping function and to it's future SSB functionality. It doesn't exist on QDX, and so a firmware solution for QDX is not possible.
Is the inductive spike damaging transistors on QDX?
Hans and I have had a lively debate on that subject, with he of the opinion that the energy level is too low to do damage, and I of the opinion that it is responsible for some, perhaps many of the fails attributed to high SWR.
A big problem in resolving the question is forensics: How do you know which mechanism is responsible? A dead part looks the same either way, and usually winds up in the trash!
JZ KJ4A
On Fri, Aug 25, 2023, 10:12 AM Daniel Walter via groups.io <nm3a@...> wrote:
John,
Your explanation of QDX L14 makes sense. It doesn't seem to be a serious problem for semiconductor failures tho. More of an issue for spectrum 'dirtiness'. The diode would take care of both concerns.
I wonder why it could not be taken care of in the QDX firmware, as it has been with the QMX. There doesn't seem to be the memory and processing constraints of the QCX, even though it doesn't have the capacity of the QMX processor.
--
73, Dan NM3A
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Maybe I could shift some of those BPF and LPF numbers around to get closer to the peaks....
What you think?
I could not have even done this without the stuff Rick sent!
73
Karl
KI4ZUQ
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It works! It receives! I removed the 22pf C403 and here are the results:
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Re: QMX Display Brightness
Rick,
I think he actually means it's too bright. I have changed the limiting
resistor on every QCX-mini and now QMX that I've built. Just too
bright, especially at night. No, I don't have the pin 3 touching the
inductor.
-mike/w1mt
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On Fri, Aug 25, 2023 at 11:20?AM Rick NF6G <rdante@...> wrote:
Dan, take a look at this thread. You may be having the same problem. /g/QRPLabs/message/107812
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Re: QMX Display Brightness
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Karl