Re: SWR and PWR does not show lcd
For test switch please display voltage ON.
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Re: SWR and PWR does not show lcd
I've tried your recommendations several times, and it doesn't work.
I've attached photos of the problem.
1. PWR/SWR Display ON
2. Hardware Test - My external meter indicates 2 watts and the same SWR.
3. Transmission test in WSPR mode. My external meter indicates 6 watts and? SWR 1.2.
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Re: GPS module GY-GPSV3-NEO wont change baud!
On 07/04/2025 18:25, Michael Pupeza via groups.io wrote: HELP! I need to change my QRP Labs GY-GPSV3-NEO module, which has the UBlox NEO-7M-000 chip on it to 4800 baud, Mike, I do not know what module you are referring to. I have just checked with a uBlox M7 and find I cannot get uCenter to permanently change the baud rate. After a cold start it goes to 9600. I seem to remember I found that before... It does save NMEA sentence configuration. In the past I have used a backup battery which will save configurations. Perhaps there is a uBlox group somewhere? Might give some clue. Although others seem to have the problem Maybe some things are stored on-chip, others in flash. 73 Alan G4ZFQ the old NMEA 0183 standard for the TinyTraker3 APRS units. I can use the UBlox u-center25.03 and everything I receive and send from it appears to work, telling me that the RS232/TTL interfaces that I try are correct. However, going into Messages View - UBX - CFG - PRT - TragetUART1 (or any other) setting BAUDRATE to 4800 and hitting the Send button makes NO CHANGE (EVER). It stays at 9600 Baud!
Is there another way to try this and make the change permanent? Perhaps there is an inhibit connection on the chip? Or some sort of authorization command? Connecting a terminal program gives me the continuous GPS strings so the module is correctly putting out my location etc., so that part is also working fine (at 9600).
I appear to be stumped! Miniature GPS units running at 4800 Baud are pretty rare and I want to resurrect my Altoids Box Pocket Tracker with one to make it truly pocket size, again.
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Hello all,
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Long time lurker, first time poster here. I recently built a 60m-15m QMX and I am having some trouble getting good reception on 15m and 17m (see attached RF sweeps). I should mention that I am using a Rev 1 board purchased in 2023, but with a mid-band component kit from 2024. Here’s where I’m at:
- I get good power (4-5w at 12V) out on all bands, and my LPF sweeps look like the firmware manual
- 60m-20m RF sweeps look more or less like what’s shown in the manual. I use a QRP Labs 50 ohm dummy load for the sweeps.
- When I connect to an antenna, I can hear FT8 signals on 40m and 20, but not on 17 or 15
- Because the lower bands seem to receive OK, I suspect an issue with L401a, C401 or C403. However, 20m uses L401a and C401 and is OK, but 17 also uses those and is not good.
- I reflowed solder on all 3 taps for L401a and the capacitors, with no change. I’m pretty confident I’ve burned off all the enamel at the junctions at this point. I get continuity at all the points shown in the Rev 1 manual (plus at pin 6 of IC402, which I think makes sense because I’m using all 4 connections for L401 instead of just the 3 with the low band version)
- I did a factory reset, with no change
- I’ve counted the number of turns on 401a more times than I’d care to admit, and keep coming up with the same number I’m supposed to have (24 turns, tapped at 15)
- I confirmed that C401 and C403 are the correct values printed on the component, and don’t appear to have any physical damage
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Trying to figure out my next steps, but coming up a bit short. All I can think of is to replace capacitors, and possibly re-wind L401a. Or, even less ideally, replace IC402. I don’t have an oscilloscope (or any real expertise to use one), so my ability to diagnose is somewhat limited. Before I start swapping out components, is there anything else I should try looking at? It’s been fun building this kit and I have managed to iron out quite a few kinks along the way by reading posts on this forum. However, this one has me stumped.
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Thanks in advance
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Alex, N7ADH
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Re: QMX+ no power output, low SMPS bias current
On Tue, Apr 8, 2025 at 06:51 AM, Stan Dye wrote:
- when you measured the output, did you have a dummy load attached?? hopefully so, unless your scope has a 50-ohm termination option turned on (but most inexpensive scopes don't have an internal 50-ohm termination).
- when you measure, are you measuring ms would be 100mW).?? So please first confirm your measurements.
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Please do not measure the output of a QMX using the internal terminator of an oscilloscope, you have a good chance of magic smoke coming out of the oscilloscope.
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Re: QMX+ no power output, low SMPS bias current
I believe it said to 'solder' it under the board, not 'put' it under the board, which would mean soldering on top.?
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Re: QMX+ no power output, low SMPS bias current
I have successfully used the 330 ones from this Amazon kit:
It is best to use a hot air station to remove/replace, since the contacts are underneath.
I have an inexpensive hot air station, and mask off all nearby components (on both sides of the board) with aluminum tape or kapton tap to hold them in position while I do the hot air work, otherwise they may blow out of position, because their solder may also liquify.
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Re: QMX+ no power output, low SMPS bias current
Looks like the L501 is broken.? Guess I'm ordering parts, and trying again.
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Re: QMX+ no power output, low SMPS bias current
First a couple of basic checks on your measurement setup -
- make sure your scope and probes are set up correctly: most scope probes have a? 1x and 10x option, and it needs to match that same option on your scope, otherwise the readings will be incorrect by 10x
- when you measured the output, did you have a dummy load attached?? hopefully so, unless your scope has a 50-ohm termination option turned on (but most inexpensive scopes don't have an internal 50-ohm termination).
- when you measure, are you measuring peak-to-peak voltage of the sine wave, or an RMS value?? Most scopes report both; peak-to-peak is probably best for debugging
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If the above are done correctly, you are seeing very low power out of the QMX, but real power.? 4W out should be about 40Vp-p, but Tune SWR default is 50% voltage, so about 20Vp-p.?? The 5Vp-p you measured would be 62 milliwatts (5Vrms would be 100mW).?? So please first confirm your measurements.
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If they are correct, it means your BS170s are not amplifying the signal much, if at all - or maybe all your LPFs are turned off due to no bias current, so the signal isn't coming out.
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Most often we don't have a bias current problem, but Jeff has noted that sometimes the L501 gets broken (one of those 330uH coils), or C504 (the big tantalum capacitor) fails.? So you could check those two items.? Also check that L504 and L514 are soldered in properly and not cracked (since I understand they are a bit fragile) - and that your diodes are not soldered in backwards.? Any of these could cause havoc with the bias current.
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Stan KC7XE
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Re: QMX+ no power output, low SMPS bias current
In a spirit of double and triple checking everything, I rechecked continuity for my connections on T507 and T501.? T501 had intermittent continuity between two of the primary windings.? After reflowing the connections, I am now getting a signal out of the BNC connector when I hit Transmit and the SWR has stabilized going into the dummy load at close to 1.0 (except on 6m, which is fluctuating between 2 and 4).? However, I am still getting the extremely low SMPS bias current, and Diagnostics still reports 0W output.? The power meter on the dummy load is showing a little power output (possibly as high as 5W for 160m and 80m, but going down for successive bands).
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Re: 750 Hz Square Wave from #QMX Speaker while Transmitting
#qmx
#beacon
I suspect that the QMX hardware is generating the steady fixed volume 750 Hz square wave and outputing it through the earphone jack only during beacon transmissions.
This only occurs when the QMX is left in USB or LSB mode during the QMX's built-in beacon transmissions.
This report is merely an observation. There is no apparent malfunction as the transmitted beacon RF is a clean single frequency signal.
AD5DZ also reported observing 750 Hz square waves /g/QRPLabs/message/139807
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Re: Release of version 2.0 of ABS solution for QMX+ (Automatic internal antenna tuner, internal battery and internal speaker with audio amp)
#PSU
#QMXplus
#audio
#ABS
#ATU
Looking to start a very limited group buy in ZL for the boards only. The other components including hardware etc. Can be selfpurchased from Digikey for about NZD 70 WITH FREE SHIPPING The cost for five boards from JLPCB at today's exchange rate is approx NZD 470 including shipping from China making it approx NZD 92 each.
The order will include the ATU and audio board,? battery/speake board,, front and rear pcb panels.
The cost should cover domestic
shipping from my qth to non rural NZ.
We have three hands up and looking for two more to make it cost effective.
Any ZL QMX+ owners Looking to join please contact me
73
ZL1REY
USPS Shipping fee is US$50.55 to Austria.? I'm not sure if there is any customs fee; I think not, but maybe some.
But that is high enough that it negates the savings of a group-buy, so it would likely be more cost effective to order items directly.
Unless what you value is the convenience...
Stan
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Re: QMX shutting off at 10.5V
Chris, Ludwig,
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Thank you very much for your returns, now it starts to make sense to me. I won't have time to troubleshoot before this weekend as I am away but I am looking forward to the debugging. Right now I would put my money on something pulling down the 3.3V power supply but I could be wrong of course! I just hope that it isn't the microcontroller.
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73,
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Yannig F4IUJ
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Re: Available Hand Mics for QMX SSB ?
Got mine today. Very excited! Thanks, so much Erik!!!!
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73 Michael N6QP
Up in Thin R
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Hello, I just completed a QMX build and had a power-up issue.
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I used a lab PSU at 7V initially; QMX draws ~150 mA right away - not proper.
But at the same it did power-up and display lights up.
So I tried USB connection and was able to flash the firmware successfully.
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- it self-turns on;
- MCU probably thinks it is underpowered: as soon as it boots and displays normal view, it shows "Shut down!" and cycles;
- display backlight blinks randomly - again, power stability issue?
- draws too much power: I dared to try to turn it on with 9V and got almost 1A consumption.
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I double-checked all components, especially on power boards and found no fried parts or soldering issues.
I also checked the 8-pin power board connector; it is the only board getting the incoming voltage, is this correct?
I don't see constant grounding on PWR_ON pin (unless left knob is pressed).
There's no measurable impedance between power and ground on the power connector if the power board is removed.
I also checked for notorious Q103/Q104 short before building - not a known V4 problem, but just in case.
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What else I can check? I assume the problem is within 8-pin power board; could it be somewhere else?
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Thank you in advance.
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Just finished my QMX+ and really enjoyed the build. Built a QDX a couple of years ago and it has been great.
Powered up at 9 volts and no smoke! Draws about 100 ma and audio out can be controlled and tune appears to work and mode / band does something. Connecting an antenna increases the noise so it appears the receiver is working.
But nothing appears on the display except for the backlight. Turned the pot from stop to stop with no results.
I’m going to touch up all 16 of the display header pins. What a bad place for a soon to be 83 year old duffer to be soldering. Why couldn’t that bave been added to the display board before mounting?
Any other thots?
72/73
Jim w0nkn
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Re: Internal mic seems to be working?
#qmx
#ssb
While I'm not sure how bad it sounds on the other station, and I understand that it is less than ideal, I was able to make another SSB contact over the weekend using the internal mic. The station in UT gave me 53 and my report was 55.
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Since the internal mic is enabled for noise input, I think it still works when used alone without the external mic. Of course the sound may not be so good without noise cancellation.
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73,
Yoon KM6KJI
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Re: QMX+ no power output, low SMPS bias current
I picked up an oscilloscope multimeter, (50MHz bandwidth) and checked the signal coming out of the QMX+ and got some interesting results.? When I tried to transmit through the Diagnostics in the Terminal, I got nothing, but when I used the Tune SWR function, I got clear sine waves on every band except 6m (to be expected as it's outside the bandwidth of the scope).? On 160m and 80m, for example, it was a roughly 1V signal.? On 60m it was closer to 5V.
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It's been decades since I did any EE in college, and signals processing/RF was never my strong suit.? What else should I be looking at?
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Just finished "building" my QMX+ and everything works as advertised! Got lazy and tried a couple of FT8 contacts on 20. Kentucky, Indiana and Brazil in short order on an end-fed dipole.
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I'm impressed, Hans. Thank you for the contributions you've made to the community.
--
Brent DeWitt, AB1LF
Milford, MA
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What bands on the qdx?
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Larry
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Carol KP4MD
Michael N6QP
Brent DeWitt