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Re: QMX+ points A continuity check to ground question
On Tue, Apr 8, 2025 at 08:38 PM, Steve Sutterer AK0M wrote:
On p25 in section 2.8 of the rev 3 assembly manual, it clearly states “Check that there is NO DC continuity from the points marked A, and ground.” ?This would be after T501 is installed.True, you are correct.? Sorry, I didn't mean to completely discount that.? I thought you had missed the statement before that, just under the photo, it states "Now check for DC continuity with a DVM between all the points marked A in the photograph above." -- because this is the main soldering test for the primary windings, and the reason those particular A points were chosen.? The test between these A points and ground is a second test that verifies that the primary didn't get shorted to the secondary (which is connected to ground), or to some other grounding point. Stan KC7XE |
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Re: #qmx mid-band receive
#qmx
#troubleshooting
Looks much better now.? If you want to experiment with taking off another turn on L401a or L510, it won't hurt anything.
And leaving it set to share 15/17 rather than 20/17 will also work fine - the only side effect I know of is that you will need to remember to make this setting again whenever you do a factory reset.
Just also remember to evaluate the changes by listening to received signals - is it better, and good enough for your liking?
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I'm wondering a little what makes the 'top' of the 15m BPF only get up to about -12.? It would be better if that were higher.?? Maybe adjusting L510 would help with that, but I'm not sure what all causes it.? It is a little lower than on your first plot of that band, so something about removing turns may also have affected it.?? It may be interesting to see if bunching the turns together would make that go up by increasing the Q of the filter - if so, removing another turn and bunching them a bit may give better results.? But I am way out of my depth here -? I can only guess at cause/effect.? So hopefully someone else can comment.? Attenuation could be coming from the LPFs or from efficiency of this filter.
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One note to remember about the RF and LPF scans: the scale on the LPF scans is made by normalizing some set of the passband values to 0dB, and making everything relative from there on each scan; whereas the RF scans measure dB values offset from a common reference (the fixed level of the test signal clk2).? So when the top of the RF scan is down like that, it does indicate a lower signal level getting through.
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Stan KC7XE |
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Re: QMX+ points A continuity check to ground question
Hi Stan,
On p25 in section 2.8 of the rev 3 assembly manual, it clearly states “Check that there is NO DC continuity from the points marked A, and ground.” ?This would be after T501 is installed.
Thanks for the explanation of the mosfet protection diodes.?
I will have this board and T501 in hand on Thursday and hopefully figure out why we are seeing continuity to ground after T501 is installed, even though the windings on the uninstalled T501 show no continuity.? 73, Steve AK0M
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Pulse modulation on QLG2 / progrock output frequencies
I am using a GPS QLG2 to supply 1 second pulses to a progrock, the progrock is generating 27Mhz for a AD4351 DDS and 24Mhz for a receive function. On both the signals generated there is a "blip" when the 1pps fires, I have removed the bright green external LED I am using to no avail, also there is no modulating pulse if the GPS is not locked. This may be an old problem, any help appreciated 73 Dave |
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Re: #qmx mid-band receive
#qmx
#troubleshooting
Thanks Stan, this is great. The explanation makes perfect sense to me. I ended up removing three (!) turns from the 15m portion of 401a. I think I could possibly benefit from removing one more. Or possibly removing a turn from L510 since the windings are about as equally spaced out as I can make them. In any case, here are the new sweeps:
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17m still looks pretty bad, and 20m is getting close to the edge. I thought I would try reconfiguring 17m to use BPF 0 instead of 1 (so sharing with 15m instead of 20) and I get the following result:
This seems better than on BPF1, but I'm not sure if setting it up this way would have any unintended consequences. Any thoughts on whether I should try taking another turn off of 401a or call it close enough? Thanks again for your guidance -?
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Alex |
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Re: QMX+
Touched up all display board connections and now I get two lines on the right side of the display. Mostly symbols and 8s and 9s. I can use the rate push to select all 9s hoping to
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hear WWV but no joy. I can find some cw signals that sound good but no sure where they are. Some SSB but hard to tune in. Progress but as still some work to do. Jim w0nkn On Apr 7, 2025, at 10:28?PM, james jones <j2@...> wrote: |
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Re: VARA Rise/Fall Threshold Changes Affect JS8?
Yes, I have run FT8 and JS8-Call successfully as well with those settings.
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The rise and fall settings had something to do with correcting the double flash low audio error code. I do not know what if any optimizations can be made to those values.
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FT8 and JS8 tone times are slow enough it should work fine with min samples at default. I had to decrease the value so the fastest VARA FSK mode would properly modulate.
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I do not know if there is another way to set parameters.
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I believe the settings are stored in non-volatile memory, so you only need to set them once. I have not had need to change the settings from the ones I found to work well for VARA so it's been set it and forget it with my QDX (I do need to adjust the per band audio levels a bit more but that's on receive)
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Cheers
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- Jadon
KJ7RBS
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New Chat: QMX Bricked
#chat-notice
Group Notification
A new chat has been created: I have been enjoying the 10-20m QMX for several weeks.? I used two 1N4001 diodes to drop the voltage to about 10.5V.? I had a beacon set on 10m.? Antenna SWR was 1.2.? Everything worked great until today.? The diodes melted and the QMX is dead.
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I took the unit out of the case but there was no visible damage.? HELP!
By: w8mv@... Do not reply to this message to post to the chat. You can participate in chats only through the group's website. |
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Thank you
Stan, Ludwig, Dan, Jeff and all the others, whose names I cannot remember at this moment, for all your time and effort in volunteering to help others... And of course Hans, for designing and providing such an excellent product at such low cost. You are all invaluable gems that give us hope in this rotten world. 73! de Bekir TA2RX |
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I have another feature request.
I'd like the ability to set a "Custom USB Name" like you added to the configuration menu in the QDX.
Hopefully that isn't too difficult.
I have 4 QMX variants that I operate remotely and it can be chore to determine which is which sometimes.?
Thanks for all your fantastic work, Hans!!
--
Randy, N4OPI |
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Re: Startup issues with QCX Mini (Rev. 3)
Thanks, Ron. I’ll definitely start there. Tnx & 73, Rich On Tue, Apr 8, 2025 at 5:54?PM Ronald Taylor via <wa7gil=gmail.com@groups.io> wrote:
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
On Tue, Apr 8, 2025 at 05:57 PM, Bill Jobes wrote:
I'm suggesting a WIKI on troubleshooting how-to procedures and techniques, not being told to take an action while presuming all readers know how to do it.?Yes, this would be very nice. Unfortunately, I don't know who would offer their spare time to provide good write-ups of how-to procedures for all of these.
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But the nice thing is, if there is a wiki recommendation that you don't know how to do, just ask here - and someone will likely jump in and help - there are tons of examples of this behavior in the message archives.? And then with a little effort from someone, the procedure could be added to the wiki.
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Stan KC7XE |
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
On Tue, Apr 8, 2025 at 02:34 PM, Bill Jobes wrote:
Ludwig and others have already documented troubleshooting approaches for the most common problems in this forum's wiki.? The fluctuating power/bias current is not a common problem with a known solution that can be easily documented. Also, keep in mind that everyone on this list is a volunteer.? I haven't added to the wiki, because I just haven't taken the extra time to do so - it does take time and effort to make a good wiki posting.? You are welcome to help by consolidating responses (like the one I just provided to Andy, and other responses to posts about the same problem) and add them to a new wiki entry for fluctuating bias current.
That is very much an exaggeration, Bill.? Keep in mind that Hans has sold many thousands of QMX/QMX+ radios.? And only a small percentage of people assembling them have reported issues - yes, when reading this list it seems like everyone has issues, but only those who do are posting them here - without counting, I venture to say far less than 10% (a generously high estimate) of all QMX/QMX+ kit builders report problems.? And some of the most common of those problems were avoided with recent versions of the hardware - so the numbers of problems have significantly decreased. I agree with Ludwig.? The WIKI is already here, and already has ideas for many of the most-common problems. What I think we need is more help in making more good entries to that wiki, derived from successes recorded in the many forum posts, and perhaps a better overall roadmap pointing to the appropriate entries for different categories of problems.
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One reason QMX/QMX+ are as inexpensive as they are, is because they are user-supported.? If Hans had to take the time to write a good troubleshooting guide for all of the problems we find solutions for, he would have to charge twice as much for the radios.?? His current documentation and assembly guides are excellent, far above what some other vendors provide for much more expensive radio kits.
Stan KC7XE |
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
I will do that once the radio is back in hand. |
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
Ludwig you ask "Why not the current WIKI?"?
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Mostly because there are often suggestions to do this, do that, check this and check that, without offering specific advise on exactly HOW to execute the suggestions.
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I'm suggesting a WIKI on troubleshooting how-to procedures and techniques, not being told to take an action while presuming all readers know how to do it.?
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
On Tue, Apr 8, 2025 at 02:34 PM, Bill Jobes wrote:
the radio is now enroute to Jeff Moore, whom I am positive will cure it.Please let us know what he finds.? This is a very tricky problem, with many possible causes. Stan KC7XE |
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
On Tue, Apr 8, 2025 at 02:11 PM, WB9YXA wrote:
The Duty cycle on the Bias SMPS always shows 0%, even as the current jumps around in the red.This is a bit different than some others have reported, where their bias smps is maxed out. This suggests that the processor may be sensing a higher-than-needed current, and trying to reduce it.
Maybe this suggests a problem with the bias control circuit (Q501, Q502, Q516 and surrounding components), or some other signal shorted to the tx_bias line.
This really is a tricky problem. |
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Re: QMX+ RF output fluctuates wildly
#QMXplus
#troubleshooting
On Tue, Apr 8, 2025 at 02:11 PM, WB9YXA wrote:
What bothers me is that the output power seems to jump around wildly.? If I go to the diagnostics screen and key the transmitter, the Bias SMPS shows fluctuations in current that correspond to the fluctuations in the output power.?There could be many causes for this.? Some are assembly-related, some are board smd soldering issues, and it could also be a failed component or bad port on the processor. ?
Here are some of the assembly-related things to check for bias current issues, via inspection and your multimeter:
- Make sure L504 and L514 (two of the through-hole inductors you put in) are properly soldered, and not cracked.? This type of inductor is a bit fragile, and it is easy to break them with a little too much force.
- Make sure your diodes are all installed the correct direction.
- Make sure L501 (the small 330uH coil) has not been broken from the board during assembly.
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Some board SMD soldering issues to check that affect bias current:
- make sure C504, the large tantalum SMD capacitor, is properly soldered on both ends.? Also test that it is not shorted internally.? Jeff W1NC said he has found C504 soldering issues and failure in some boards he has repaired.
- verify the soldering of Q501, Q502, and Q516.? One user found that Q516 was poorly soldered.? You need to check these under good magnification.
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Hopefully one of those will hold the solution to your? particular problem.
Good luck, Stan KC7XE |
Braden Glett
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