Re: 10 watt linear HF amplifier - stability issue/question
#10W_PA
Changing the input/output cables made the change. Now the amp is stable, the only remaining issue I have that I measure around 20-21dB gain...
Thanks for the help!
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
I am running my QMX up to 2:1 without any issues so far, generally stop tuning at 1.5:1. Don't feel the case warming up. Doing only CW at this SWR though.
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Peter
HB9EBE
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Re: #bug #qmx QMX SWR protection not working when QSK is enabled?
#bug
#qmx
Adrian,
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some times ago there was a post from Hans about a special situation using QSK. Maybe Q507 isn't controlling the PA voltage and the PA gets hot using QSK. Until now (no SSB) you will notice this only using QSK and IMHO maybe also in case of SWR protection. ?
You may test for this.
Use "Menu - Hardware tests - SWR measurement". Connect a dummy load and external power meter. Check the output here (using 50% PA voltage ore less) and compare to regular transmitting (100% PA voltage). If the output is (nearly) the same, Q507 didn't work well.
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You may check also using Terminal - Diagnostics.
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73 Ludwig
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Re: QMX+ High Current and Self Start
I¡¯m fairly confident in the repairs I made to the 5V SMPS and it seems to be working fine. To validate the LCD, I removed it to rule out any issues. No performance change noted.?
With a departure from that, I remembered some QDX troubleshooting which resulted in finding sorted PA mosfets. I did originally have to replace Q507 and the PA¡¯s due to shorted failures.?
I¡¯ve been probing the board with my DMM and decided to remove the PA¡¯s. Sure enough, the high current draw and 4.6V drop cleared up without them in circuit. Early this morning, I started fine tuning the inductors and did some basic RX tests etc. Despite the PA¡¯s dumping power, RX seemed fine.
So, What in the world would cause the PA¡¯s to be gated and dump all that power to overload? Why would this happen in RX? There shouldn¡¯t be current flow if I¡¯m not mistaken.?
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Additionally, pressing the encoder to turn the radio on does not work. I actually have to press my fingertip to Q105 to latch it on. Pressing the encoder to power down the radio ¡°works¡± but there is a current draw of 0.065A until I remove the plug. Trying to restart the radio does not work until it is unplugged.?
I¡¯m starting suspect IC503 and the MCU. I¡¯m not wanting to reinvent any wheels so any and all advice to move forward is graciously appreciated!
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QMX+ test ADC I/Q shows one phase missing
We finished assembling the QMX+. ?When performing the ADC I/Q test we observe no I phase present on all bands(flat line). ?Q phase looks fine. ?Looking at the possible trouble shooting issues it would indicate faulty pre-amp or defective PCM1804. We do not currently have an oscilloscope available. ?We are wondering if it is a component we installed that may be the culprit. ?Anyone have this issue before? ?
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Thank you
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Re: New Build but can¡¯t get firmware to load
I also had the same problem and the fault was on the 3.3V SMPS board.
The solder had been repaired, but it was short-circuited.
I used a desoldering wick and now everything is fine.
Tarmo K?lli
ES4RTK
Lots of measurements and I KNOW it¡¯s a solder issue.
At which place?
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Indeed, the problem should be at PCB#2. It looks like the
values are from the pin header, right?
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In this state (analog regulator) VDD at the pin header comes
from the 78M33. Because different current across D102 and D103
the voltage is a bit below 3.3V.??? 2.96 V is ok here.
We don't see VDD produced by the SMPS. But we have ADC_3V3
produced from the SMPS VDD by the voltage divider R110 and R112.
ASSUMING (!) this divider is correct the SMPS VDD is around 2.3
V. In one of your former posts Diagnostics show 2.58 V. I think
in this operational state the voltage shown by Diagnostics are a
bit higher than real (see VCC = 4.96 V measured by DMM and 5.52
V shown by Diagnostics).
PWM_3V3 = 1.19 V is the mean value from the switching pulses.
With 2.9 V for ON (see voltage of the signal PWR_HOLD at ON from
the controller) the Duty cycle should be around 41 %. In your
former posts 42% and 43% were shown, this fits.
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To find the problem at PCB#2 you should test this board off
line (see QMX QMX_Plus Power supply test Process).
For step No. 3 reduce the input voltage below 1 V and set a
current limit of around 50 mA!!! Doing 3.1 increase the input
voltage slowly and check the input current and VDD. Question: How much input current at which input voltage? Do
you have a sudden current increase or is this linear to the
voltage?
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73, Ludwig
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On 16/09/2024 15:30, Mark Palmer via groups.io wrote: I expect someone's already asked this, but I can't find any reference here.
Has anyone converted a QMX+ to operate on 70 instead of 50MHz? Mark, A quick search for "QDM 4m" produces /g/QRPLabs/message/110602 from the horses mouth Well, QDX is pretty much the same. 73 Alan G4ZFQ
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Re: QMX+: The trifilar toroid torture test
Thanks, everyone.
Honestly, if it had not been the end of a long day happily hyperfocused on all the tiny toroids, I probably would have figured this out for myself. My spouse also suggested different coloured nail polish, although I don't know off hand how well that would "stick".
Michael WD0OM
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Re: The $200,000 Question
Just to close this out, I wound up winding for 12V after (almost literally) flipping a coin.
On Sun, Sep 15, 2024, at 08:39, Michael - WD0OM wrote:
Trigger cables? Not so far. I suspect another noise source.
On Sun, Sep 15, 2024, at 06:35, Bob KB1TEK wrote:
Have you found these cables to be noisy? ?I have one and it¡¯s terrible. I guess it could be the power bank.?
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
On Sun, Sep 15, 2024 at 10:15 AM, Sandy wrote:
Very simple. 1:1 is the max safe SWR. I use a 4 state tuner to get nearly there and then fine tune while broadcasting until the SWR indicator on the QMX reads a perfect 1:1.
I use the same tuner and have an MFJ.? I suspect I may have some issues with both that I have not yet had the time to look into further.? I also have a Rigexperts antenna analyzer, but I can't always get all the way to a 1:1.? My 4SQRP seems to make my SWR on 20M worse.? I think I can get it less that 2:1, but I finally put the analyzer on my antenna clean (no tuner) and am about 1.2:1 so I figure that is okay.
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As I have said several times, I know 1:1 is best.? My QDX and my QMX+ (when built) are both for 9V for what that may matter.? And I can check my SWR several ways, but just wanted to know how far off of 1:1 was redlining.? So far the only answer I got was 1.5:1 should be okay.? Would like to know if 2:1 is okay (knowing that it is NOT optimal).? Just want to avoid having to replace finals... but may have to just play till I blow a set.
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Bob
KG5GTE
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I expect someone's already asked this, but I can't find any reference here.
Has anyone converted a QMX+ to operate on 70 instead of 50MHz?
73 Mark G?OIW
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#bug #qmx QMX SWR protection not working when QSK is enabled?
#bug
#qmx
Hello all,
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Since a few FW versions ago, I kept my QMX on 30m band, on a doublet tuned with a manual Z-match. Today I felt like doing 20m and I retuned the antenna. To my surprise, the SWR protection didn't trip - although the S was displayed on the screen and the sidetone gone silent, the QMX happily countinued to emit RF. Being on 027 firmware, I proceeded to scratch my head in order to ascertain what new feature could cause that, since I'm positive that SWR protection worked ok some versions ago.
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First thing that came to mind was the QSK and, sure enough, after disabling it, SWR protection worked as intended. I had QSK on "auto" before.
I searched the group for similar occurences and haven't found anything, but, in all fairness, I didn't give it too much time either. Has anyone else observed this?
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Regards,
YO3GFH
op. Adrian
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
Dan,
Similar experience here. I suspect the majority of people with QRP Labs equipment have seen the same. With reasonable care to minimizing SWR mismatch and duration of the mismatch, risks are low for magic smoke exit.?
--
73, Dan? NM3A
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
I'm with Mike.?
The nanoVNA is such an incredibly useful tool, I wonder how I survived without one. It also pinpointed a feeder break to the centimeter, just one of the many magic tricks it contains.
I've also been pretty careful since I bought the QCX classic and all the radios from QRP Labs that inevitably followed. So far my spare pack of finals has remained unopened.?
73s Ted?
2E0THH?
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Re: Short USB cable for QMX to reduce RFI pickup
I had run into a similar situation. And this solved it:
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Although a better solution is to be sure to add a 17 foot (for 20 Meters) or longer (for longer than 20 M) counterpoise wire when tuning a single long wire. It connects to the other post on the antenna tuner and can just run out along the ground. Remember that all circuits need somewhere for electrons to travel to, which is why we have 2 wires to connect pretty much everything. Antennas are no different, 2 wires are needed, but if only one is supplied, the other needed "wire" is sought out by the RF circuit causing havoc.
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When operating a hand-held walkie talkie, for example, your body becomes that "other wire".
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--
73
de Roy - KI0ER
Littleton, Colorado USA
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Re: QMX+: The trifilar toroid torture test
Michael,
Good advice from others to follow. I used three different color wires to make my transformer, but marking them with colored markers would work just as well.?
As far as inserting them in the proper holes, leaving the wires long and using tweezers does work well, but the best method is to cut them all different lengths from front to back. Then you can guide them in one at a time without having prior wires pop out. See Hans description of how to assemble the QRP Labs dummy load (in the manual) for a great description with photos.?
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73, Dan? NM3A
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DDS VFO Synth display choice?
Hello all,
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Some while ago I built the DDS VFO and I can say it works very nicely! Only change I mad was to use a green/black LCD module, then I did not need the backlight. Good for QRP /P operations.
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I am thinking of connecting the DDS into my new homebrew TXVR that I am building for backpack portable using.
But here is my problem. The LCD display module is 70mm X 24mm and the mounting board even bigger.
That takes up lots of space on the front panel of my small TXVR! And to be honest I do not need all the two lines of characters. Just need the frequency display
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I really want something smaller. I have searched and all the Hitachi HD44780-compatible displays are this large size.
Is there any way to use a smaller display? Even if I loose some info. As above i just want the frequency digit.
Does not have to be pin compatible because I can make wire connection adjustments.
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Any ideas?
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
I meant QRP Labs ...
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73, Dan - W2DLC
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Re: QDX and QMX+ (soon at least) what is the max safe swr?
I'm not particularly careful at all. I have an MFJ-971 which I tune for max noise, then a short transmission to get as close as possible to 1:1, which I almost never achieve on either my balanced dipole, or my EFW. I've also used MFJ 949E, and QRP Guys mini tuners. I've been using QRL Labs transceivers for almost 5 years and never blown a final. I have an original QCX, two QCX minis, a QDX, and a QMX. I built them all from kit form, and I keep a bag full of BS170s in the shop just in case, because of all the horror stories I've heard here. I don't know what I may be doing differently, but I've had a lot of success with BS170s withstanding some fairly high SWRs. I suspect it may be because I don't stress myself with trying to squeeze the last milliwatt out of these transceivers.?
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73, Dan - W2DLC
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Hi Thomas?
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You could try if usb powered in the terminal from the command line?
Run Tracker?
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The U4B does not run from USB power without a terminal (computer) ... usb power tells the radio that it is connected to a computer and so it runs the usb connection program? . I always check using? battery power before a flight or in text edit/ debug/r which should also work
in Basic make sure there are no extra spaces at the beginning or end of your lines and if you are using 2 digit line numbers make sure the starting number is on the far left and the first line is at the very top of the page. Make sure you compile after any change and wait a second after compiling.
Dave VE3KCL
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Peter HB9EBE
Mark Palmer
Ted 2E0THH
Daniel Conklin
VE3KCL