Re: QMX susceptible to ESD
#qmx
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On Mon, Mar 24, 2025 at 09:56 AM, Jerry Gaffke wrote:
It should be possible to add normal AM reception to the QMX through a firmware update,?
Synchronous AM as well.? Once you have an I-Q data stream you can do any kind of demodulation you want.
73, Don N2VGU
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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:
Generally for high power amps LTspice reaults are bluesky
in practice.? It cannot apply all of the strays and parasitics
of the end circuit.? I've used Genesys at work but the
license will take your breath away.
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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
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Post online only,?
direct email will go to a bit bucket.
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Nate,
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Some additional details:
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In that old thread I pointed to, I suggest L502 is causing larger voltages across the BS170's than there should be:
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?That file with four different LTSpice simulations shows why I think this is the case:
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The first of the four simulations is a model of the QMX as it arrives from QRP Labs, the maximum voltage across the BS170's is 40v.
When looking at the QMX with a scope, we can see even higher voltages across the BS170's, sometimes more than 60v.
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In the second simulation, L502 has been removed.? The maximum voltage across the BS170's is now the 24v we would expect.
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In the third simulation, a simple series LC circuit is used instead of the multi-band LPF of the QMX.
Now the voltage across the BS170's is a nice square wave, not the sharp peaks of the second simulation.
The current through the BS170's is a sinusoid.
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I feel that L502 is not appropriate here, making the QMX amplifier a weird cross between a Voltage Mode Class D amp
and a Current Mode Class D amp.? In the fourth simulation is the equivalent Current Mode Class D amp.
Here it is the current through the BS170's that is a square wave, and the voltage that is a sinusoid.
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For those that don't have the free (and highly recommended) program LTSpice installed
to simulate these things, I have added a pdf of the LTSpice schematic to the files section:
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Jerry, KE7ER
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On Mon, Mar 24, 2025 at 06:46 AM, Jerry Gaffke wrote:
Nate,
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When Allison says a max of 16 volts, she means the power supply into the rig.
Transmitting on 80m with the QMX from a 12v supply into a 50 ohm dummy load can cause
peak voltages of more than 60 volts from drain to ground at those BS170's.?
And 60v is the absolute max listed in the BS170 datasheet.
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In addition to reading the datasheet for the FET's, you also need to know how the circuit works.
That is not a trivial task, unless like Allison you have spent a career doing this stuff.
Here's a tutorial on a Voltage Mode Class D push-pull amp such as used on the QMX:
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Why such high voltages?
As described in that tutorial, the action of transformer T501 causes twice the power supply voltage to appear
across each BS170 when it is not conducting.? In addition, the LPF in the QMX blocks
the undesired harmonic currents from going out to the load, which raises voltages further.
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For those wishing to see what's going on, I'd recommend using
the LTSpice simulator on a model of the QMX final.? Such a model can be found
in the left-most of the four simulations found in this file:
The discussion is in this thread:??
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Jerry, KE7ER
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On Mon, Mar 24, 2025 at 05:20 AM, Nate Reik wrote:
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On Sun, Apr 25, 2021 at 10:53 AM, ajparent1/kb1gmx wrote:
There is some magical thinking with regard to RD15hhf parts.
RTFM, in this case, the data sheet.
First its a 16V max part.
Can someone explain this? I'm trying to understand maximum values of RF transistors...and the RD16HHF1 datasheets I see don't say 16v anywhere. I see 20v and 50v ratings...and I see things about rules of thumb elsewhere...but how do I determine from the datasheet of an RF transistor what the maximum DC supply voltage is?
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Thanks for any help with my learning!?
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-Nate
N8BTR
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Applies to LINEAR push pull amps.?
The 50W amp is not linear and the rules are not quite the same.
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Generally for high power amps LTspice reaults are bluesky
in practice.? It cannot apply all of the strays and parasitics
of the end circuit.? I've used Genesys at work but the
license will take your breath away.
?
--
Allison
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Post online only,?
direct email will go to a bit bucket.
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>>>>I see 20v and 50v ratings...and I<<<
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The 20V is a hard limit gt gate brakdown votlage.? ?The 50V is the peak voltage
the drain can see in operation before the internal silicone goes back to sand.
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The device was specifically designedd for 12V nominal? use.? To do that you
need margins as peak RF van easily exceed 3X 12V and 4X unders poor swr
is not unlikely,
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The IRF510 is a 100V device...
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--
Allison
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Post online only,?
direct email will go to a bit bucket.
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>>in a 50 watt amplifier, I want to replace the IRF510 with the RD16HHF1.<<<
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NO!? The pinout is not the same making for odd crossover mods.
? ? ? ? ? The max operating votlage for RD16HHF1 is 16V, no exceptions.
? ? ? ? ? ?The max power is 16W per device and a pair cannot do 50W
? ? ? ? ? ?without emitting smoke.
?
--
Allison
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Post online only,?
direct email will go to a bit bucket.
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Stephan, My 80 meter band phase error calibration graph looks like yours. Another ham said to check where the band center is in your band configuration menu and make sure it is actually set to center and not to 0. I will check this with mine later today.
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73, Dan - W2DLC
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
Screenshoot 80m phase error after factory rest
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Re: #qmx #SSB Firmware beta 1_01_003 release
#qmx
#ssb
I have a similar pattern in the ‘80m phase error vs DAC’ as Mario Vano AE0GL. I have done a factory reset, no change. Any ideas for troubleshooting?
Many thanks to Hans for the SSB software. I made the first SSB attempt successfully with a 40m SOTA chase.
Stephan, DD6DO
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On Mon, Mar 24, 2025 at 03:04 AM, Chris wrote:
I found that for a recent version of Hamlib the QRP Labs radios has been changed from one version that handled all QRP Labs radios to separate "QRPLabs QCX/QDX" and "QRPLabs QMX" radios. To add to the fun only the QCX/QDX one worked with my QMX, the QMX one caused WSJT-X to shut down.
This is correct,? and is the issue.
No need to update or change WSJT-X.? ?If you have Hamlib v2.6.1, simply choose QDX or TS-480 as the radio type.? The QMX type is broken in this version.? You can see the version of Hamlib at the lower left of the radio configuration screen.
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Optionally update to hamlib v2.6.2 or greater,? where they fixed this bug.? No difference in functionality.?
Stan KC7XE?
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Chris, I've been working through this series of YouTube videos...I think Allison may have recommended them previously. I've yet to download LTSpice, but the videos cover that, too.?
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-Nate
N8BTR
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On 24/03/2025 12:49, Alan G4ZFQ via groups.io wrote: Hamlib is here Sorry, the best place to get it is here It tells you where to put the file. 73 Alan G4ZFQ
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Re: Simple and very tiny mic for the QMX.
#qmx
#ssb
Thank you Ronan. I could not remember what it was called.? Tinsel wire. YUK!
Even if you do manage to get that stuff soldered,? it will likely not hold up to any strain whatsoever.?
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regards,
Bryan, N0LUF
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On 24/03/2025 13:23, Chris via groups.io wrote: The 'improved' versions are 'authorised' as they are made by one of the developers as a way to trial additional features, Chris, "Authorised" in so far as it is open source. The variations are not promoted on the main WSJT-X page. Like the RC versions "improved" versions are best used by more experienced users. The current stable version is covered by the official user manual, the WSJT-X group and probably used by the majority. I see confusion when features of modified versions are mentioned. 73 Alan G4ZFQ
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Re: SSB Calibration blown finals
10 meters but they give good output on 6.
Tony
AD0Vc
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On Sun, Mar 23, 2025 at 11:15 PM, mux_folder2001 wrote:
What is the highest frequency you are using the TN0110s on?
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Re: SSB Calibration blown finals
This is a 9 volt build. It is supplied through an LM338 regulator adjusted for 9 volts. The regulator input is from a 12 volt linear bench supply. The BS170s came from Mouser. They were mounted normally.
Tony
AD0VC
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Fascinating. ? ?Would be more so with :
supply voltages that blew them?
power outputs that blew them?
where the BS170’s came from?
how they were mounted?
别迟肠…?
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Re: SSB Calibration blown finals
In the QMX+ I just mount them face up with the washer as usual. In my QDXs I have experimented extensively with heat sinks and I found that heat was never an issue. I do not run WSPR, mainly FT8.
Tony AD0VC
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How did you deal with the reverse mounting/heat sink issue? I have purchased a set of those transistors just in case.?
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Brien - KE7WB
Donald S Brant Jr
Daniel Conklin
DD6DO