Adrian, ? My QMX bandpass is actually skewed upward like yours (rather than downward as I posted).? In fact, have a look at my attached 80m sweep.? Our 80m sweeps are so close we could almost perfectly overlay one on top of the other. Other bands look like your ¡°before¡± images as well.? So, I am encouraged by your C402 mod.? I¡¯ll tackle it this weekend when I install the 1N4448 safety diode at Q508. ? Many thanks for the providing this information.? It will likely save me and others from hours of L401 adjustment tweaks.? ? Paul, W9AC
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Re: QMX FT8/WSJT-X Usage Problems
Hi Hans,
You were right on. Hooked up dummy load and it worked like a charm. Shack RF was problem.
Any suggestions for? a ferried USB-C cable, most seem to be to short. I could also add my own clamp on filters.
I keep seeing the following on screen - 14074.00 "S.'
What does the "S" mean ?
Thanks for the quick come back.?
K2OI
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Re: QDX MOSFET Heat Sinks
Oh my, Jim...
How do you dispose of something like that?
JZ
Yes, Jim? that is correct. Some day it could wind up somewhere that has no such control. My conscience is quieter if I don't use it.
BTW, do you remember the BeO envelopes on high power transmitting tubes? Same safety consideration noted.
73, JZ
John,?
The article you cited includes this:
"the material (beryllium oxide) is safe to handle as long as dust is not generated during machining or handling."
73 Jim N6OTQ
Hi Don,
I had a similar thought, but then did a bit more digging.
I found that Kyocera also offers a similar thermal product called Q-Bridge:
Most of those are also Aluminum Nitride, although some are made of Beryllium Oxide, which is quite toxic.
Unlike most electrical insulators, which have very poor thermal conductivity, those two ceramics possess thermal conductivity on par with metals.
Pretty cool! (pardon silly pun :-)
This class of part could be extremely useful as the envelope gets pushed on cig-pack sized Ham radios!
73,? JZ
On Sat, Jan 6, 2024, 11:10?AM Donald S Brant Jr < dsbrantjr@...> wrote: On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.?
I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....??
The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material.
73, Don N2VGU??
|
Re: QDX MOSFET Heat Sinks
John, I have a block of BeO from a Motorola conduction-cooled?PA stage.? It's dangerous because all the block edges are as sharp as knives. ?
Naturally, BeO is something you don't want to drop on a hard floor.? Asa ceramic, it's subject to breakage, which could generate and spread dust.
73 Jim N6OTQ?
Yes, Jim? that is correct. Some day it could wind up somewhere that has no such control. My conscience is quieter if I don't use it.
BTW, do you remember the BeO envelopes on high power transmitting tubes? Same safety consideration noted.
73, JZ
John,?
The article you cited includes this:
"the material (beryllium oxide) is safe to handle as long as dust is not generated during machining or handling."
73 Jim N6OTQ
Hi Don,
I had a similar thought, but then did a bit more digging.
I found that Kyocera also offers a similar thermal product called Q-Bridge:
Most of those are also Aluminum Nitride, although some are made of Beryllium Oxide, which is quite toxic.
Unlike most electrical insulators, which have very poor thermal conductivity, those two ceramics possess thermal conductivity on par with metals.
Pretty cool! (pardon silly pun :-)
This class of part could be extremely useful as the envelope gets pushed on cig-pack sized Ham radios!
73,? JZ
On Sat, Jan 6, 2024, 11:10?AM Donald S Brant Jr < dsbrantjr@...> wrote: On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.?
I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....??
The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material.
73, Don N2VGU??
|
Re: QDX MOSFET Heat Sinks
Yes, Jim? that is correct. Some day it could wind up somewhere that has no such control. My conscience is quieter if I don't use it.
BTW, do you remember the BeO envelopes on high power transmitting tubes? Same safety consideration noted.
73, JZ
John,?
The article you cited includes this:
"the material (beryllium oxide) is safe to handle as long as dust is not generated during machining or handling."
73 Jim N6OTQ
Hi Don,
I had a similar thought, but then did a bit more digging.
I found that Kyocera also offers a similar thermal product called Q-Bridge:
Most of those are also Aluminum Nitride, although some are made of Beryllium Oxide, which is quite toxic.
Unlike most electrical insulators, which have very poor thermal conductivity, those two ceramics possess thermal conductivity on par with metals.
Pretty cool! (pardon silly pun :-)
This class of part could be extremely useful as the envelope gets pushed on cig-pack sized Ham radios!
73,? JZ
On Sat, Jan 6, 2024, 11:10?AM Donald S Brant Jr < dsbrantjr@...> wrote: On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.?
I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....??
The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material.
73, Don N2VGU??
|
Re: QDX MOSFET Heat Sinks
John,?
The article you cited includes this:
"the material (beryllium oxide) is safe to handle as long as dust is not generated during machining or handling."
73 Jim N6OTQ
Hi Don,
I had a similar thought, but then did a bit more digging.
I found that Kyocera also offers a similar thermal product called Q-Bridge:
Most of those are also Aluminum Nitride, although some are made of Beryllium Oxide, which is quite toxic.
Unlike most electrical insulators, which have very poor thermal conductivity, those two ceramics possess thermal conductivity on par with metals.
Pretty cool! (pardon silly pun :-)
This class of part could be extremely useful as the envelope gets pushed on cig-pack sized Ham radios!
73,? JZ
On Sat, Jan 6, 2024, 11:10?AM Donald S Brant Jr < dsbrantjr@...> wrote: On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.?
I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....??
The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material.
73, Don N2VGU??
|
Found the solution to this problem here:
/g/QRPLabs/message/116094
Evidently the firmware file was corrupted preventing the QDX from initializing and making it appear unresponsive
The post linked above referenced a point on the board where I2C_SDA could be held low while powering up, but is applicable for a Rev 2 board. Mine is a Rev 3 and the test points near those referenced are not the same.
I had to go to the EEPROM and hold pin 5 low while powering up. Once the front LED starts rapidly flashing then remove the low off pin 5.
This caused the EEPROM from being read and the DFU put the QDX into the state where one can copy the fresh firmware file via the USB to the? QDX file system and the rewritten to the EEPROM.
All is back to normal now.
73,
Kevin K3TL
|
RIGHT ENCODER BUTTON DOESN'T WORK
Hi
I assembled the KIT, and it works, but the right encoder button doesn't activate the functions as it should. When pushed it acts as the left encoder button.
Of course, the hardware test (in terminal mode) shows the activation of the left button when the right button is pushed therefore, the push button test for the right encoder fails.
The same behavior is also for the right tactile button. After pushing the right encoder I cannot even exit from the menu and shut down the QMX (I need to disconnect the power supply) I have checked the control board several times and all connections and continuity of the main board connector with the STM. All is ok. I also tried factory resets and different firmware
versions without luck. Any suggestions for this very unusual issue?
Thanks and Best 73 de I1MDQ Nino
|
Re: QDX MOSFET Heat Sinks
Comparison chart is from this source: JZ On Sat, Jan 6, 2024 at 12:15?PM John Z via groups.io <jdzbrozek@...> wrote:
Hi Don,
I had a similar thought, but then did a bit more digging.
I found that Kyocera also offers a similar thermal product called Q-Bridge:
Most of those are also Aluminum Nitride, although some are made of Beryllium Oxide, which is quite toxic.
Unlike most electrical insulators, which have very poor thermal conductivity, those two ceramics possess thermal conductivity on par with metals.
Pretty cool! (pardon silly pun :-)
This class of part could be extremely useful as the envelope gets pushed on cig-pack sized Ham radios!
73, JZ
On Sat, Jan 6, 2024, 11:10?AM Donald S Brant Jr <dsbrantjr@...> wrote:
On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.
I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....?
The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material.
73, Don N2VGU
|
Re: QDX MOSFET Heat Sinks
Hi Don,
I had a similar thought, but then did a bit more digging.
I found that Kyocera also offers a similar thermal product called Q-Bridge:
Most of those are also Aluminum Nitride, although some are made of Beryllium Oxide, which is quite toxic.
Unlike most electrical insulators, which have very poor thermal conductivity, those two ceramics possess thermal conductivity on par with metals.
Pretty cool! (pardon silly pun :-)
This class of part could be extremely useful as the envelope gets pushed on cig-pack sized Ham radios!
73,? JZ
On Sat, Jan 6, 2024, 11:10?AM Donald S Brant Jr < dsbrantjr@...> wrote: On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.?
I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....??
The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material.
73, Don N2VGU??
|
Re: QMX 10-20m LPF0 problem?
Hi again Jo... We continue the Scandinavian collaboration but others are welcome to chip in too ;)? I give my numbers below. Thanks for encouraging me to measure everything. It might be useful in the future for a base line. I have not tried to increase the sensitivity by changing the L401 in any way, and I can't reproduce your 20M inconsistency as far as the image sweep is concerned. I hope the numbers will be useful for you. My general impression is that my QMX is working perfectly in every way, regardless of the numbers ;)
QMX high band rev 2
RWTST transformer
12V
1_00_014
50¦¸ dummy
Audio sweep:
30M -12dB Sideband rejection ~-50dB
20M -10dB Sideband rejection ~-55dB
17M -4dB Sideband rejection ~-45dB
15M -6dB Sideband rejection ~-35dB (~-22dB at worst position)
12M -9dB Sideband rejection ~-55dB
10M -15dB Sideband rejection ~-60dB
RF filter sweep (best number when peak is outside of the band noted between parentheses):
30M -11dB
20M -11dB (best -9dB at 15.5-16.5 MHz)
17M -4dB
15M -6dB
12M -9dB (best -8dB at 23-24.5 MHz)
10M -15dB (best -12dB at 20-27.5 MHz)
Image sweep:
30M -27.9dB
20M -34.3dB
17M -33.4dB
15M -34.9dB
12M -27.8dB
10M -27.8dB
Power output @12V (measured as DC voltage from a dummy built according to https://sites.create-cdn.net/sitefiles/72/2/1/722175/DL-2_HF_Load.docx.pdf)
30M 3.3W
20M 3.9W
17M 5.2W
15M 5.4W
12M 3.9W
10M 4.1W
Good luck tampering with your rig. I hope kit building will be an addiction for you in the future.
Anders
|
Re: QDX MOSFET Heat Sinks
On Sat, Jan 6, 2024 at 07:16 AM, John Z wrote:
The thermal wick chips I mentioned in the previous post offer an
interesting possibility for the future (especially if the price comes
down!)
Those "thermal wicks" sure look a lot like a regular chip resistor with no element; maybe that is exactly what they are.? I wonder what the thermal properties of an ordinary high-value (1M?)chip resistor might be.....?? The few I looked into had alumina substrates; not as good as aluminum nitride but better than air or PCB material. 73, Don N2VGU??
|
Hello Paul,
Those are after adding 470pf to C402; the OP (Lun Yang BD8BTE) and I had the same issue with the 80m sweep, which was a bit low. In particular, my 60m was also a tad off.
Lun added 330pF, I couldn't find anything except 470pF :-)
Please see below the "before and after" sweeps:
80m BEFORE
80m AFTER
60m BEFORE
60m AFTER
40m BEFORE
40m AFTER
So, by the looks of it, 470pF shifted the center down by some 1.5 - 2 MHz for 80, 60 and 40. Right now, I'm listening to the 80m band and it doesn't seem like any great improvement, but this isn't of course very scientific :-)
One thing that I forgot to mention, after adding the 470pF cap to C402, all sweeps looked totally crazy so my heart sunked into my pants, thinking that I've managed to fry something... turned the thing on and off, but no change. But after a full factory reset, all seem to be ok now.
73,
YO3GFH
op. Adrian
?
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Re: QMX version 2 - brilliant
Love the success stories, don¡¯t hear a lot here! ?Glad your build went smooth, as I¡¯m starting the build here soon. ?Congratulations!
--
Trevor (N0YMA)
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Adrian, I¡¯m not sure if these are before or after C402 mod images?? Can you include both sets?? I¡¯m facing the same issue here and have considered first tinkering with the L401 windings. Bandpass center is shifted downward quite a bit on all bands. ? ? Paul, W9AC ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Adrian YO3GFH via groups.io Sent: Saturday, January 6, 2024 10:15 AM To: [email protected]Subject: Re: [QRPLabs] QMX Rev2 80m RF sweep good enough? #bpf #filter #qmx #80m ? Having nothing better to do, I added a 470pF in parallel with C402:
Looks like 40m is affected too by the change, I suppose that's normal since, in the band cofig screen, 80, 60 and 40 seem to use the same BPF.
73,
YO3GFH
op. Adrian
|
Having nothing better to do, I added a 470pF in parallel with C402:
Looks like 40m is affected too by the change, I suppose that's normal since, in the band cofig screen, 80, 60 and 40 seem to use the same BPF.
73,
YO3GFH
op. Adrian
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Re: #qmx PCB Rev 2 recommended modification
#qmx
Stephan, I'm glad it works! You may wish to tack that wire to the PCB in a few points. It might move around and cause damage otherwise.
72 & 73 JZ
Dear all,
Hooray, the QMX rev. 2 is on the air. The protective diode (1N4148, package SOD323) has been soldered in and the IC402 has also been replaced.
Soldering SMD components is a bit of an adventure for me. When desoldering the IC402, I tore the PAD for PIN14 off the board. It was unlucky that the line goes directly to the processor and could not be reached at another component nearby. Luckily, this line arrives at PIN51 on the processor, which is easily accessible at the corner. Not nice, but it works.
73, Stephan
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Hello Lun,
The RF sweeps (not the SWR sweep) are to be run into a pure resistance dummy load.? The dummy load matches the filter design of 50 ohms impedance.? An antenna will likely not have a pure 50 ohms resistance, skewing the results.
Power measurements should also be done into a dummy load as the impedance impacts the accuracy and actual power.? The directional coupler (called a Stockton Bridge in some references) used in the QMX is accurate for power measurements only when the load matches 50 ohms.? As the impedance deviates, it will still be representative, but it is not entirely accurate.? That is not the case for the SWR, as it is a ratio of the forward and reverse (reflected) values VSWR = (VFwd+VRef)/(Vfwd-VRef).
73
Evan
AC9TU
|
Yep, the tech is as old as dirt. It's all in the math of the L/C (Elsie) calculations. When you hit the sweet spot, all is well. Variations in core materials, capacitor tolerance, and winding technique will necessitate some tweaking of the windings, spreading, narrowing, adding, or removing a turn as needed. It's all part of the fun!
--
72/73 de Steve, K9NUD
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Re: QCX 50W PA multibanding?
#50wpa
On Sat, Jan 6, 2024 at 12:20 AM, Muhsin TA1MHS wrote:
why? for each band you'll need not only different LPFs?but also different bias settings
73
muhsin TA1MHS
I understood that,...I was trying to ask what the effect was of NOT changing the bias settings in a different band. I'm assuming power output...but was curious how much different. 73 -Nate N8BTR
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Paul Christensen
Donald S Brant Jr
UPNORTHOF48 :
K9NUD-Steve