Re: QMX and power bank PD
Bruce, the topic is using PD power banks. Not wall chargers. I've been doing it for years myself. I even wrote an article for QRP Quarterly on the subject back in mid 2020. Wall chargers are indeed potentially subject to the condition of the power served to your wall socket. This much is true. Personally, I'd rather plug a radio into a regulated source when operating on AC, or worse, on a generator.
When I go to Field Day and operate QRP, I do low-power battery powered as the category, and I only use PD battery banks. The ones I've tried that actually supported the voltage/amperage my trigger cable is negotiating have worked just fine. In fact, the original 2020 article involved using an original QCX with the BaMaTech enclosure.?
Lots of other people have replicated my results, including one person from my local club that had a friend operate using the same trigger board I did, with a power bank that I suggested in a presentation I did for my club, the Phil-Mont Mobile Radio Club in Philadelphia. This person had no trouble operating all weekend with a decent power bank, and even charged his phone at night from the same bank.
I'd have to say it's a mature methodology at this point. -=-=-=-=-=-=-=-=- 73, Gwen, NG3P
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Re: QMX Mid Band Rx issue
I had a similar temperature-related issue with my QMX.? It would have loud 'digital' noise for several seconds, then be perfect.? And I took it out on a POTA activation, and the noise lasted longer at startup, then was fine.? But after the sun went down and it got cold outside, the noise returned and didn't go away, and I had to qrt.
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Such noise can be caused by a cold solder joint somewhere.? So at home I took the bottom cover off, and turned it on and let it warm up to proper operation.? Then I tested it a bit by using canned air to briefly spray different parts of the bottom of the circuit card, hoping to find the location of a cold solder joint by getting it cold. [Canned air is very cold when it first comes out; at work we used to use a freeze spray for this purpose].? When I sprayed the PCM1804 chip, the noise immediately returned, and it would go away quickly if I warmed it up with a hot air gun (set to a moderately low heat).? I repeated this several times, trying to reduce the area I was cooling/heating to determine the source of the error.?? After a few tests, I could cause the noise to come with a short blast of air right on the PCM1804, and it would go away again if I touched the chip with my finger for a few seconds to warm it back up.? So in this case indeed it was the PCM1804 chip.? I replaced it, and the problem completely disappeared.
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After I replaced the chip, I realized that I never tried to just reflow the solder on it, in case one of the pins had a cold solder joint.? I should have done that, so I don't really know whether it was a failed chip or a soldering issue.? Could have been either thing.
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Stan KC7XE
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Re: USB-C to USB-C cable recommendation
Surprisingly enough, Ikea makes some decent cables.?
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Re: Orientation of D33 on QCX-Mini Rev3 PC
Those 1956 eyeballs still have lotsa miles left in them. But after 11PM they seem to go a bit haywire.
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Jim
VE4BWG
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Re: USB-C to USB-C cable recommendation
Essager is good brand with good quality for the price. Combine it with usb isolator modul and you are safe.
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On Mon, Dec 23, 2024 at 12:41 PM, David Wilcox K8WPE wrote:
You might want to cover the inside of the case with copper foil
No RFI problems both in or out at my shack at current setup. Power is low enough, all ground loops eliminated, usb isolated, single point grounding, coax cables cut to lenght to avoid any accidental resonace with used bands. Noise that i have are mostly the things everyone living in the city have and we cant help it.?
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Good idea for anyone who is willing to try copper tape or similar just for the piece of mind.
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Having the same issue. Got it working for several days straight. Then turned it on a few days later and it can't find the microphone again!
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Re: QMX Mid Band Rx issue
Some more on the QMX mid band high noise.
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First let me describe the issue. Turn on the QMX. Very loud static/noise. After about 10 seconds, the noise becomes intermittent, and then goes away entirely.? At that point the QMX works perfectly.? The noise is about 20 dB louder than the ambient band noise. Until today, I was just going to live with it.
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Today, I did a SOTA activation with my QMX. The noise continued for several minutes. I thought, uh-oh, I'm screwed. The noise then stopped, and all was well. I did a few on/off cycles to see what would happen. The noise would last about 10 seconds.? There is one key difference between today, and all previous uses of the QMX. The QMX was in my backpack for about 2 hours. The outdoor temperature was 45-50 degrees. This is the coldest I have used the QMX.
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Questions:
1) Is this the same noise others have been hearing ?
2) Has anyone found it to be something other than the PCM1804 ?
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73,
Steve, N2IC
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Re: QMX+160-6 ceased powering up
#QMXplus
Many thanks Chris,
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i'll try to acquire a regulated power supply during the Holidays and get back to you in January.?
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Sly VA2YZX
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They are not intentionally crossed; it is best practice to avoid crossing the wires on the windings.
However as you note, it will not have a noticeable effect on the functionality.? When orienting the ends to solder in the transformer, it is very difficult to do without crossing the last turn a bit.
Stan KC7XE
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Re: 12V battery not playing well with QMX
I would use a pre-made buck-boost converter, like this one I got from amazon:
or just search for buck boost converter -? there are multitudes of models, some with meters, etc.
You set its output for 12.0V (as measured by your DVM), and if the input voltage is higher, it regulates it down, and if the input voltage drops lower, it boosts it up to 12.0V.? Works very well to give a constant regulated voltage to the QMX.? And it is very small, so you can attach it to the housing of your battery.? Like any converter, it is not 100% efficient (varies between 85% and 95% depending on voltages), but that only reduces the runtime from your battery a small amount, while it removes any concern about the voltage level into your QMX.
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Stan KC7XE
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Re: USB-C to USB-C cable recommendation
I bought some great cables from? Fannoday on Amazon.com recently. They are very good quality, high speed shielded cables at a reasonable price.?
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73, Dan - W2DLC
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Re: Orientation of D33 on QCX-Mini Rev3 PC
No problem Brent, glad to help, we’ve all been there, you’ve only got a few years on me. 1961 vintage myself. Cheers Nick G0OQK
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12V battery not playing well with QMX
Hello all,
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When I go portable, I use a 12V Makita drill battery which voltage varies between 12 and 10.5V. It is really convenient, the circuitry protects against shorts, it is in a robust case and it lasts a good while.
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Nevertheless it doesn't play well with the QMX, for some reason sometimes the tension goes up while in RX. I imagine, there is some unintended interaction between the QMX regulation and the battery while the current draw is low.
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I can't really "afford" the 0.5V drop of a regulator in emission thus I would like to add in between the two a simple linear regulator that auto switch itself in the circuit as soon as the input tension goes above 12V.
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Anybody would recommend a circuit that is a good starting point ? Even if I need to make modifications/adjustment, a "scheme design" would help me.
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73 de Yannig - F4IUJ
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On Mon, Dec 23, 2024 at 03:57 PM, Corey M wrote:
Hi Dave, I am curious what type of RFI you experienced, I have not experienced any with my 3d printed top. 
Looks really interesting. Have you got more photos to show?
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73 de Yannig - F4IUJ
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Re: RF output power on 160 and 80 meters
On Monday, 23 December 2024 17:29:13 -03 Chris KB1NLW via groups.io wrote: Until Hans fixes it through programming a lower PA voltage for 160m
and 80m I would recommend against operating or not operating above
10v supply since the PA transistors are actually operating above the
manufacturers rating even with a 1:1 SWR.
Dear Chris, Allow me to be a little bit confused by your statement. Are you referring to drain current or maximum power dissipation @ 25°C? What does the frequency have to do with the operation of the PA if it outputs into a pure resistive load of 50Ohms? Provided the frequency is far enough to the lower end of the transit frequency. Which is the case for 160 and 80m. People are fine with a SWR of 2:1 or even 3:1 because the resistance, which the PA is driving, is higher than 50Ohms. BS170 blow when SWR is high when the resistance is lower than 50Ohms. SWR does not indicate in which direction the mismatch goes. 73 de -- Eike Lantzsch KY4PZ / ZP5CGE
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Hi
I am looking at the WTS transformer instructions, and notice that the wires on the non-tapped side of the primary seem to be crossed. Is this intentional or a trick of the light.
I don’t think circuit wise it makes any difference but thought I ought to check.
73 and season’s greetings
Stewart/G3YSX
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Re: QMX+ with Macbook Air (Sonoma OS)
Folks, I cannot tell you how fantastic it is to
see so much help offered here with this group.
I am fully up and running now and everything seems
to be just fine.
Anecdotally, I have a UNIX working relationship
from my engineering days at work (long time ago) I could get
around the BSD flavor rather well in those days.? Alas, it has
been many years since I was near to anything running Unix and
the closest I have been was a Raspberry Pi a distant relative.?
I have been using Windows like everyone else it seems forever.?
I tried to load putty on my Mac with similar
experiences of failure.? I had to install mac-ports and
home-brew but it never worked so I gave up and asked the
question in this forum.? After learning how seamless it was and
waking up old UNIX directory and input/output nomenclature in my
cobwebbed mind,? it was so easy I am embarrassed that I could
not figure this out.
My apologies to Stan Dye who was spot on as far as
how the QMX serial environment appeared to the Mac-book. He had
it right and I had it wrong!
Lastly, I am getting MacLogger and some other
stuff to play with.
A huge thanks to all!
Joe
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Re: RF output power on 160 and 80 meters
Until Hans fixes it through programming a lower PA voltage for 160m and 80m I would recommend against operating or not operating above 10v supply since the PA transistors are actually operating above the manufacturers rating even with a 1:1 SWR.
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Re: QMX and power bank PD
On Mon, Dec 23, 2024 at 11:01 AM, Bruce Akhurst wrote:
This can get confusing so do I end up tying the right cable to the right charger?? ?I'd rather buy a dedicated supply . .
I agree with that - particularly since the wall chargers are also often 'noisy' in their generation of the DC voltages.
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But when using a PD Battery power bank, the confusion factor is not there, and the power is reasonably quiet.? If you are using 12V, you do need to make sure the PD battery you buy supports 12V (not all do, but it is easy to see in their spec).? All of them do 9V, per PD spec, so I built my QMX for 9V.
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Stan KC7XE
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Gwen Patton
Ivica - YU1QRP
Daniel Conklin
dxradio33