Re: Multibanding the 50w amp question
Sam, I think others have found that without changing ferrite materials, output above 17m is pretty poor, if it works at all. If you look up some threads about 10m builds of this amp, the changes are discussed and laid out.?
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To answer your question, there would not be significant sacrifice. Some rigs are set up this way, where the highest LPF is always in line. I've had considerations of doing the same, making a 40-15m amp.? Currently though, I have a 50w amp built for 20m, that I have run on 40m with an external 40m LPF added in line. Output on both is as expected.?
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One LPF board to look at/consider:
The 3 band LPF version is only 5cm x 5cm! Problem is that I'm not sure that a 5 pole LPF would be enough with this Class C amp, especially if covering more than one band with that LPF.
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-Nate?
N8BTR
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Re: Figuring out why no keyer sound and updating my QMX Menu Reference to Firmware 1_01_003
A bit complicated to set up at first, but then just plug-n-play.
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Multibanding the 50w amp question
Hi all,
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I have an unbuilt 50-watt amp kit and I'm trying to figure out how to best build it. I just completed a 5-band (40-15 meters) homebrew rig (it's not a QMX, but it works!). I'd like to use the amp on multiple bands for this radio (and possibly a QMX). I am thinking of just building the amp for the highest band I need and adding a switchable external low-pass filter.
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But I had a question: obviously the output of the amp won't be as large on higher bands. However, if I build the amp for 15 meters and transmit on say 40 meters (with a 40 meter external low-pass filter) should I still similar output as I would get if I built the amp for 40 meters, or would there be a significant sacrifice running though the 15 meter filter first? I'm sure some of you have experience trying this out. Thank you!
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72, Sam WN5C
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Re: Figuring out why no keyer sound and updating my QMX Menu Reference to Firmware 1_01_003
On Sat, Mar 29, 2025 at 12:07 PM, Stan Dye wrote:
Actually, for CW mode, you can connect the QMX to your computer, enable the I/Q mode, and use SDR software as a panadapter,
That sounds interesting for when using at home, but complicated.
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Re: Should I just go ahead and order a QMX+?
N9LFF
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The QMX plus is clearly a mature design for cw and digital modes. I delayed until I had time to build it, on my bench now. Best to not be in a hurry during assembly. If you are ready to build, order it. Have a plan B for Field Day to take off all pressure. Enjoy the journey.?
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Curt
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Re: 74ACT08 damaged and LCD is all blocks
Oh Stan,? you embarrass me.
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Re: 74ACT08 damaged and LCD is all blocks
Hi Ludwig and Stan,
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I'd definitely check BS170 as well. Once removed from the PCB, IC503's Vcc to gnd seems to be open, so if it was causing short, it would have to be done via BS170 I guess?
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I'd provide some more context. I finished building this QMX+ a few days ago. It had good TX/RX. Power output on 20/10 was a bit more than 4W. Compared to my previous QMX HB build, its MDS is 10dB better and its SSB tx from mic doesn't have the constant 2kHz tone in the background like my QMX HB does. I was very satisfied with its performance. I believe the BS170s had been working fine before. This morning I was setting up the shack for WPX and I wanted to power it with a dedicated USB-C charger with 12V PD trigger. I tried a few times to turn it on from that 40W Anker charger without success (LCD went off after showing "Initializing audio..."). A few minutes later, when powered from the known good charger/battery, it started to have the symptoms I described in the original post. So TX was never attempted with that suspicious 40W charger. I'll check BS170s later today. I do have lots of new BS170s - I ordered them last year with PCM1804 and 3253. Maybe I should order SS14, D108, D109 as well just in case..
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PS I didn't install the BFP/LPFs for the 160/80/60 bands. Not sure if that's gonna cause problem.
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73 N6HAN
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
On Sat, Mar 29, 2025 at 05:00 PM, @Ludwig_DH8WN wrote:
On Sat, Mar 29, 2025 at 08:10 PM, Pawe? H wrote:
software glitch
Pawel, I'm not sure about software. I'm also not sure about ESD. Maybe it is a unstable PCM1804. There are reports about PCM1804 working wrong related to temperature. Maybe here something is similar.
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73 Ludwig
I think that's possible too. After several hours experimenting with band configuration settings and calibration settings, my QMX+ suddenly started screaming in my ear on one band and developed a little digital sounding irregular beeping noise on certain other bands. After I let it cool off over night, it seems to be back close to normal, but I noticed that the audio noise levels seem to return to max volume on some bands when I cycle through them. I suspect some damage to the PCM1804 because the symptoms seem similar to others who have had PCM1804 failures.
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73, Dan - W2DLC
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Re: Should I just go ahead and order a QMX+?
I think we have already gotten this year's big new thing from QRP Labs, in the form of the SSB update.
To speculate on the new thing for 2026... perhaps a QMX XL? Something with a larger display and a more base-station-like configuration?
Gwen, it is already listed on the website, see the link in the left-hand column under the QMX+ heading.
It is complete with the beginnings of a detailed description, and what to expect.
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My two cents:
It is unlikely that you will risk your QMX*, but a very small handful of people have reported hardware issues after installing, that disabled their QMX until fixed.? It is not fully known whether those hardware problems were the fault of the update, or due to pre-existing conditions, either internal to QMX or external in their setup, that may have been exacerbated by the update.? So if you want to avoid that risk, wait for another beta update or two, or for the full release.
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Most of us have had no major problems, but there are still some bugs and quirks in the new SSB mode and getting it configured and working as well as it should on all the bands, that affect a good number of users, but not all - it may depend on your particular QMX.? And those are what generate most of the messages recently in the SSB-related threads.?
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And many of us have successfully found workarounds to the issues which Hans has not yet fixed, such that using SSB has been great fun on our QMX*!
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Stan KC7XE
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Just had my first QSO.? A local ham.? Received a good audio report.? I was using the QMX+ and my "Tiny Linear".? The Tiny Linear is a 100W-capable homebrew unit.? It is in a box only slightly bigger than the QMX+.? It doesn't need band codes, you change bands manually with a touch screen.
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? To make it work, I had to modify the QMX+ a bit.? There is a 220-ohm resistor in series with the output switch for the PTT.? That was too much resistance for the Tiny Linear, which actually runs its T/R relay through its PTT input.?? How much
current?? The output switch of the QMX+ is rated 170mA.??? OK, I forget how much the linear sources, so I measured it...17mA.? So I pulled the card out of the QMX+ and shorted across the 220ohm resistor.
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Seeing 60W out on peaks.? Enough to be heard.
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?????????????????????????????? - Jerry, KF6VB
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Re: QDX Transmit Power Drops
Thank you for your responses and yes that makes sense. I wasn't thinking about how mosfets behave when overheated. I checked all the solder joints and ohmed out Q8 - Q11, T1 and L14 to see they had continuity where they were supposed to have it on the circuit board. I suspect I have either wound T1 incorrectly or I have scraped some enamel off the wire and it's shorting to an adjacent wire or the core. I am considering rewinding it with fresh wire if I can get it off the board without damaging it. I'm open to alternate suggestions. ?
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73 Doug WB5WRC
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Re: QMX+ high pitch noise on power. Now dead.
The output of the IC101
is 0V before pressing the button, then briefly goes to 3.2V, and then to 1.7V when I press it. When you press the button input starts at 12 then goes down to 10 then 8.
+V, Vcc, and Vdd are all zero without pushing the button. When pushing the button. +V = 12V. Vcc = 160 mV. Vdd = 1.6 V
Resistance to ground: +V = 25 K Ohms Vcc = 3.68 K Ohms Vdd = 202.4 Ohms
Vcc to Vdd = 1.4 K Ohms Vdd to +V = 18 K Ohms Vcc to?+V = 18 K Ohms
Is there a way I can check D109?
Thanks for all the help!
On Sat, Mar 29, 2025 at 12:10 PM, Nico Smith wrote:
On IC101 it goes to 3.2 then 1.7 volts when. I press the button.
It draws 0.7 amps when pressing the button.?
0.7A is way too much, about 3x normal, confirming something is shorting.
Also, on JP106, there is no power.
I don't quite understand your description of the voltage measurement.? Are you looking at the output pin of the IC101 regulator (the one closest to the diodes and coil)?? And it is 0V before pressing the button, then briefly goes to 3.2V, and then to 1.7V when you press the button?? Or is it 3.2V before pressing the button, then goes to 1.7V when pressing?? Or are you looking at the input pin (closest to card edge)?
It is useful to know the voltages on both the input and output pins of IC101 both before and while pressing the button, and after releasing the button.?
Also please the voltages on +V, Vcc, and Vdd before and while pressing the button.? These are found in that order, in JP105, adjacent to D108 and C107 - they are the inner set of the two rows of 3 small holes.? (Vcc and Vdd are also in JP106, where you say you saw no power, so they may show nothing again).? If there is truly 0V (or very close to 0V) on Vdd while pressing the button, you likely have a shorted D109 (i.e. it did its job in protecting from overvoltage), and hopefully no damage to the processor or other 3.3V parts.
And one more set of measurements: with QMX+ unplugged, measure the resistance between +12V and gnd, Vcc and gnd, and Vdd and gnd.? Each of these should be a few k-ohms.? Then measure the resistance directly between each of the three voltages.? These should all be very high, in the mega-ohm range.
These measurements will help diagnose where the problem is, and if there are other problems besides the likely D109.?
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By the way, looking at your setup - I would buy an inexpensive 3A drock boost/buck converter, set it to 12.0V output, and wire it into the cable coming from your power supply to your QMX+.? That way you can leave the power supply set at the best voltage for your Kenwood, and still always have the correct power set for your QMX+, ensuring power mistakes don't get made.? And depending on which model you buy, it will have a current limit you can set while debugging.? (The current limit may only work if you don't ground your QMX directly to the Kenwood, due to the design of the drok, but that's easily avoided during debug).
Stan KC7XE
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Re: 74ACT08 damaged and LCD is all blocks
On Sat, Mar 29, 2025 at 02:28 PM, @Ludwig_DH8WN wrote:
There is a current limit for the VCC rail. Duty max is doing this. So I don't believe the high current was flowing from VCC via IC503 to GND. Maybe something is wrong around the BS170
Good catch, Ludwig. I guess I was writing when you posted. You are always more careful than I am in diagnosing things.
Han, you should order some BS170, too, if you don't already have some, and Ludwig is spot-on in recommending you look around the BS170s for additional issues.
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Re: 74ACT08 damaged and LCD is all blocks
Hi Stan, sure. It's a charger (sorry I forgot the word "charger" in the original post), not a power bank. The specs on the bottom are:
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SWITCHING ADAPTER
PN: A2935 Model ASGaN83w-P40W20
Input 100-240V~50/60Hz 1.0A
Output: 5.0V=3.0A 15.0W
9.0V=3.0A 27.0W / 12.0V=3.0A 36.0W /
15.0V=2.66A 39.9W / 20.V=2.0A 40.0W
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Seems to be a 40W charger. I think it comes with my 3-in-1 MagGo charger (). I checked it a few times. I have no issue getting 9V or 12V from it with PD triggers.
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73 N6HAN
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Re: 74ACT08 damaged and LCD is all blocks
On Sat, Mar 29, 2025 at 11:45 AM, Zhenxing Han N6HAN wrote:
After removing IC503, I'm able to power it on normally. Terminal app shows both SMPS modules are working fine.
Excellent!? So glad that it is working without other damage.
And I understand completely the drag it is when you wanted to have fun in WPX.? I have been stymied for other (non-QMX) reasons.
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FYI, I have used exclusively PD power banks and PD trigger cables without any issues - but I did have to make sure the power bank unit properly supports 12V for the 12V rig (I have one QMX wired for 9V, and use 9V PD for it - but one of my power banks won't do the 12V, so I use it only for the 9V QMX).
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Best luck to you going forward, and when the new parts come, let us know how it goes...
Stan KC7XE
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Re: 74ACT08 damaged and LCD is all blocks
There is a current limit for the VCC rail. Duty max is doing this. So I don't believe the high current was flowing from VCC via IC503 to GND. Maybe something is wrong around the BS170. I see two possibility:
- The broken IC503 switched one pair of BS170 on the whole time. The high current was flowing via these BS170.
- One or more BS170 is/ are broken. Or you have a solder bridge from drain to gate. The PA voltage is switched on the most of the time (also in RX mode). So a high voltage around 12 V was shown to IC503, damaged IC503 and after this a high current was flowing via the PA failure into IC503, let explode the poor IC and made it to a simple piece of "wire" to GND. After removing IC503 this path to GND would be open now.
I would check the region around the BS170. You may also check resistance D-G, G-S and D-S.
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73 Ludwig
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Re: 74ACT08 damaged and LCD is all blocks
On Sat, Mar 29, 2025 at 11:35 AM, Zhenxing Han N6HAN wrote:
Anker 36W USB-C power brick
Han, can you share with us the exact model of Anker 36W power bank you have?? I don't see one labeled that way on their website.? Several of Anker's power banks do not support 12V PD (since it is not part of the current PD spec - I think it was in an older version of the spec). But several do support 12V PD, even the newer ones.? When one that doesn't support 12V PD sees a 12V PD trigger, they may show 11.x volts derived from another one of the protocols - but that voltage could change as current changes, since it is not in PD mode.?
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I have one Anker powerbank that supports the 12V PD trigger, and one that does not.? They both support the 9V, 15V and 20V PD triggers, which are in the PD spec.? If you look at the detailed specs for each of their power banks on the website, it shows which trigger voltages they support in USB-C PD mode, and which voltage ranges in other modes.? If it doesn't explicitly say 12V in the PD mode spec, it is not supported.
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Re: Should I just go ahead and order a QMX+?
Thanks, Stan! I'll go look at that shortly.?
73, Gwen, NG3P?
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Re: Qmx deaf on 20 meter band
Hi Andrea,
I'm not sure what would cause that.? But I think one other user reported a similar issue, and found in the "Band configuration" window of the terminal interface that his 20M center frequency had been set to 0.? So I would at least check your band configuration settings, and see if 20m looks normal for all settings, with the band edges and center frequency appropriate for 20m. (The band edges are typically set to well below and above the ham band, and that's ok - they are used for the x-axis range of the sweep functions.)
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Others may have additional ideas...
Stan
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
On Sat, Mar 29, 2025 at 08:10 PM, Pawe? H wrote:
software glitch
Pawel, I'm not sure about software. I'm also not sure about ESD. Maybe it is a unstable PCM1804. There are reports about PCM1804 working wrong related to temperature. Maybe here something is similar.
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73 Ludwig
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Paul K7VIQ
Daniel Conklin
Shirley Dulcey KE1L
Gwen Patton