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As others have reported, I have lost half of the previous output power on my QMX+ after running the calibration.?
I am beginning to suspect that I lost one or more of the transistors in the final power amplifier.? I will do some more testing to verify.? I ordered some replacement BS170s just in case. ?
The calibration routine appears to stress the finals and sort out the weak from the strong MOSFETs.
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Steve KA0SM |
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QDX: Adding a 1N4148 across L14
I have four QDX's and I've decided to add a 1N4148 across L14 as many other have done here to add some protection against accidental high SWR.??
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Digikey lists several versions, including a 100V 200ma version and a 75V 300ma version.? Is one better than the other for this application?
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Best,
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Jim
K8DDV |
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Allison and others.... To be clear, I brought up this old thread to understand the discussion about the RD16HHF1 being a "16v max" device. I have no interest in the original question from another poster in 2021 in trying to put different finals in the QCX 50w amp, or get 50w out of the RD16HHF1.
? I'm exploring a small amplifiers for POTA/SOTA etc, and trying to learn along the way. That research is causing me to want to understand the datasheet limits, so I can understand max DC voltage for transistors used in the 10-30 watt amplifier range.?
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Jerry's comments are also of interest to my exploration of reducing QDX output power and finals.?
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Just wanted to be clear that I'm not trying to do anything magical! ?
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-Nate?
N8BTR |
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Question for Hans,
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Have you seen anything like the spectrum I (and Jim) posted?? During my regular weekly QSO with a friend about 170 miles away, while he was able to copy me and it did not sound bad (still trying to get the sound bite he recorded of my transmission), he was able to corroborate that I was producing RF up and down from my Fc that he could see on his SDR SW (he runs PowerSDR).
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I am going to try a couple of different mic's (QRP Guys and Adam Kimmerly's which are on the way to me) and redo calibration but wondering if the issue will persist.? I tried using both a (connector modified) Icom HM-12 and a Behringer XM-8500 with poor results (as spectrum pic I posted previously shows).
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Also, no one replied regarding calibration with or without a mic plugged in.? From the beta page one might infer that with a mic plugged in would be correct as the calibration section follows the mic drive setup section.? It is not explicitly stated and wanted to ask to be sure.? So, mic or no mic during calibration (or does it even matter)?
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Thanks and 73,
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Robert, WA2T |
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Re: Software Development and Requirements Creep
On Mon, Mar 24, 2025 at 01:03 AM, G8JCF wrote:
The current UK population is around 69,438,564 humans, source Well if you want a more conservative estimate, then 25% of the working age population have a criminal
record too -
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Hint - thats still a lot of millions.
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Best laugh I've had all day.
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And with that, thanks for the show, no need for me to provide further input on this one.
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Do not do calibration in one set. Do it one by one with 5 minutes break in between to let the finals have some time to cool down.
toggle quoted message
Show quoted text
20:38, 24 March 2025, "Azgael via groups.io" <azgael@...>:
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Sent from Yandex?Mail for mobile |
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Congratulation Hans, this SSB firmware is a great achievement!
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Still, I have a problem! I had the a QMX plus rev 2 system working on firmware version 1_01_002, preform a calibration and all looked good, today I update the firmware to 1_01_003 reset to factory defaults and (Dummy load connected) run calibration, let it sit for a while, after a while when I came back to the desk the system was down no idea about the calibration status? since the terminal was disconnected, so I turn one the radio the fist firmware screen appears briefly than the screen fades down and buttons don't do anything, fortunately I could connect the terminal check the diagnose tool and I have the 5V SMPS voltage around 3.5 volts, so it seams calibration did something to the 5V supply. anyone else had this issue or similar?
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PS: I was able to flash the the version 1_01_002 again, factory reset and the 5V SMPS are back! ?this puzzle me?! still my normal transition power is now less than half what was before +/-5W to 1.5W in 160m as example.
?Seams that the finals might be burnt after all! |
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Re: QMX+ Strange Audio Artifact - Help, Please...
Hi Stan,
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Sorry for the delayed response to your post - busy weekend. Solder joints for L504 and L514 looked OK, but I re-heated them anyway - no change, still sounds like a 30 wpm machine gun on power down. Neither of them are cracked or messed up in any way. Every past kit I got from Hans had superficially damaged surface-mounted 330uH chokes. This kit 'appeared' to have no damage when I got it. However, near the end of construction, I noticed that the one nearest the PA transistors was also slightly damaged. It looked like the wires were not broken so I put a dab of CA glue on the plastic to keep it in place. Now, I'm wondering if in fact there was wire damage.
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Are there any voltage measurements I can do to confirm the status of that little thing? If it is hosed, I'll probably have to send the rig off to Jeff Moore for repair, as there is no way I can fix one of those things where it is located. I've done some minor SMD work in the past, but if that component is broken - not a chance.
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Regards, Jim
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Jim / K7TXA Eagle, ID SKCC 10447T BUG 301 |
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On Thu, Mar 20, 2025 at 08:12 PM, John Olsavicky wrote:
Well this mystery is solved. I had shorted the leads from one of the BS170 finals nearest to the slot that the PCB slides into. Fortunately, the only damage was to that final so I replaced it and the QMX booted right up. I was able to run the optimization again with no problems.? ?
KC3PBY - John |
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Re: Receiving AM?
On 24/03/2025 16:19, Donald S Brant Jr via groups.io wrote:
Once you have an I-Q data stream you can do any kind of demodulation you want.Yes, and the option "IQ mode" enables a SDR program to be used with a QDX or QMX to do just that. There are some decoders that use the IQ stream directly. 73 Alan G4ZFQ |
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Re: Errata for the Operations Manual
I cannot imagine, as a newbie? owner of a new QMX+, noting the documents
for grammar or punctuation errors. My prime concern is the best bang for my buck and intelligible and adequately explained concepts and instructions. Attaboy, Hans. Thank you for understandable documentation with meaning. Like all things, not perfect, but more than adequate for this old dog losing what few brains he had. First coupla FT8 contacts last night. Looking forward to cw and ssb contacts in the near future with no appearance of magic smoke; because I read and understood the documented instructions and explanations. Da Ol' Dog ??????????????????? wa4hei |
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Re: QMX susceptible to ESD
#qmx
Gary,
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I had the same problem as you.? ?Here is my solution ? /g/QRPLabs/topic/qmx_and_esd/111241054
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Brien - KE7WB |
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Indeed, LTSpice does not always agree with real hardware.
Especially with something like the QMX final and LPF's.
Some of the details don't get properly modeled.
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But it's way better than just staring at a schematic and confidently thinking?
you know how it works.? In the case of the QMX final, you are almost certainly wrong.
(Well, true for most of us anyway.)? Very educational.
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Jerry, KE7ER
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On Mon, Mar 24, 2025 at 08:41 AM, ajparent1/kb1gmx wrote:
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Re: SOTA QMX SSB
Today, I also tried the SSB firmware 1.01.003 on a SOTA actication (HB/BL-005) - see
The SSB part works perfect, but it was nice to have the QRG saved per mode instead of per band. The change between a CW QRG and a SSB QRG takes quite some time...
Anyway, Hans did a great job here, now we wait for the internal microphone to be enabled. |
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>>>>Ahhh, so thus 50v divided by 3 or 4.... Giving 12.5-16.6V. Got it.?
So it would be OK for 20v IF you had a perfect output load matched to the transistor? Makes sense. Thanks, Gary!?
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No. Don't even go there.
At 20V to get 50W out you would be very close to max Idd.? ?Assume 60% efficient that means
for 50W out you need 83W DC in and your are very close to the 5A peak Idd at 20V.? A pair could
but that tends to push the max Vdd.? To get that power you would also have to exceed max
input power or push very close to it.
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What that means is every margin needed for reliability would be at the edge.
Generally any feedline or antenna fault would kill any try.? Quickly!
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Magical thinking will not make the RD16hhf1 into a RD70HHF (a 70W device)!
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Allison ------------------ Post online only,? direct email will go to a bit bucket. |
Brien - KE7WB
Donald S Brant Jr
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