Roy,
Check the gate signals at the BS170 PA transistors.
You should see zero volts in RX, and a 5V 50% duty cycle RF square wave in TX.? If you are using a DMM to measure, that TX signal will register as 2.5 volts, an averaged value.
If you see voltages substantially different, something is wrong for sure. Either the driver circuit has a problem or an internal short has occurred at a PA transistor(s).
GL JZ KJ4A?
On Wed, Apr 3, 2024, 10:08?PM Roy - KI0ER < ki0er@...> wrote: Another clue .... I found where all the excess current is going ... the PA transistors are very hot while the QMX has only been in receive (idle) mode!? ?
I've re-checked all my solder joints under strong magnification while also looking for some stray short, but nothing is popping out at me as problematic.
Does this clue help narrow things down? I'm open to suggestions!
--
73
de Roy - KI0ER
Littleton, Colorado USA
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Re: QDX High Band Screen Shot
You can also use the Factory Reset option to reset to the default settings if you have the jumper installed for high-band operation.
73
Evan
AC9TU
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Re: QDX High Band Screen Shot
Hi Jonathan,
Here you go:
Note that it is for the latest firmware, 1_10.? I suggest upgrading if you have not done so already.
73
Evan
AC9TU
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QDX High Band Screen Shot
Would someone with a High Band version of the QDX be able to provide to me a screen shot for the Band Configuration screen similar to the low band screen here:
Thanks!
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Rather not a successful build - QMX is deaf and mute
#HighBand
#qmx
Hi gals and guys!
It's my fist message on this forum, so please let me that Hans is doing a great job with QRP Labs with his fantastic products (QCX-mini, QDX and QMX to name just a few).
Recently I've purchased high-band QMX rev. 3 and found some time to build it. Except for a few small stumbles (eg. non working buttons) I would say it was a successful build. Just a few days ago I had pretty decent sweeps (audio, RF, LPF and SWR) for all the bands except for 15m and 17m. I thought it may be some continuity problem with the T508 and T512 so I reworked the solder joints, put the radio together and... I lost TX and RX capabilities. This means no power output (on the "Diagnostics" screen after pressing T) and totally random test sweeps for all the bands: audio charts show no LSB/USB separation, RF filter shows random values around the middle part of the chart, LPF chart goes steeply to 0db on the lowest frequency and stays there until the end of the range. When I connect an antenna and power meter, I get 0W reading on transmit and barely can hear other stations (the signal is very faint). "Input Analysis" screen shows "NO SIGNAL".
I didn't touch anything else - the LPF toroids for 15m and 17m were the only thing I reworked. So I inspected all the solder joints and connections on the PCB multiple times, fixing the ones that weren't looking good enough, but it didn't help.
When transmitting, the power consumption goes from around 0.1A to 1.1-1.2A and the BS170 get warm. That's a good sign, isn't it? ;)
Any ideas what I should do next, keeping in mind I don't have any oscilloscope (just a regular multimeter and nanoVNA)? Do you have any ideas what may be the cause?
I really hope you can help me...
Have a great day,
Damian SP9LEE
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Re: Changing Frequencies from 20 M to 10 M on QMX Fast
#20m
#10m
Hi Mike,
Thank you for the tip.? I will try it in a day to two.
Richard
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Re: Something to look out for: possible cause of PA failure (QDX etc).
A big factor in thermal failure of the BS170 in any of the QRPLabs kits is that the TO-92 package is not very efficient at transferring heat away from the die.
The tinned pad, the washer and the screw do allow for 'some' contact but it is not a machined surface and even the multi-layer board can only do so much.
Steel (the washer and the screw) are not great thermal conductors in their own right.
What I have been doing is to use M2.5 copper screws, a copper crush-gasket (meant to deform), copper nut and some thermal compound to improve the heat transfer characteristics.
--
Tisha, AA4HA
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Re: [QMX] Keying CW via CAT
This is one of those QCX features that Hans has not gotten to yet for the QMX, AFAIK. I am looking forward to it, too.?
73, Mike KK7ER
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Another clue .... I found where all the excess current is going ... the PA transistors are very hot while the QMX has only been in receive (idle) mode!? ?
I've re-checked all my solder joints under strong magnification while also looking for some stray short, but nothing is popping out at me as problematic.
Does this clue help narrow things down? I'm open to suggestions!
--
73
de Roy - KI0ER
Littleton, Colorado USA
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Re: RF Sweeps Problem QMX R1
Hi,
You are my hero :)
That fixed it and I think I have a complete QMX.? ?A challenging build for me but I got it done.
Thanks to Hans for designing such s great project.
Now I have 2 more to build, and it should go together a little easier.
Kindest regards,
Tim
W8TWF
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Hi Ludwig.
Yes, the power supply is in SMPS mode. And the power output matches closely on my analog external meter.
The SWR values also closely match when I use my MFJ Versa Tuner II compared to the QRP-Labs dummy load.
--
73
de Roy - KI0ER
Littleton, Colorado USA
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Re: RF Sweeps Problem QMX R1
I've read from past posts that even though you have a fresh start with a new build, that a factory reset can cure a bad sweep display.?
--
73
de Roy - KI0ER
Littleton, Colorado USA
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Hello Roy,
It's drawing 212 mA powered up and idle, which is high!
Indeed. Around 100 mA here.
Have you checked the status of the buck converters? The 3V3 converter is working and the status is SMPS (Terminal - Hardware tests - Diagnostics)?
During the QMX start 3.3 V is produced for 0.25 sec by an analog voltage regulator causing a higher current. After the buck converter is working the analog regulater should be disabled (see schematics page 1). So far as I know it should be checked as ok before the start procedure of the QMX is finished, but maybe ...
Sweeps are not bad except Image @ 20 m. Please try again. Sometimes sweeps are not correct but after a second run or later ok.
Yes, output is (to) low. How did you measure these values? I don't know the real SWR of this dummy. But if the SWR is this bad (12 m and higher) and you measured the voltage the bad SWR causes larger errors in calculated power. Did you read the SWR from the QMX or from an externel SWR meter?
But Power @ 20 m with a good SWR = 1.09 is also to low.
TX current here is
580 mA @ 20 m and 3.5 W
600 mA @ 17 m and 3.7 W
870 mA @ 15 m and 5.1 W
700 mA @ 12 m and 3.1 W
770 mA @ 10 m and 3.7 W
For higher frequencies the current is higher for the same output.
Maybe something is wrong with the PA? The PA voltage looks ok. Could you check the signal at both inputs of T501 using an oscilloscope? Both are symmetrically?
73, Ludwig
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I just finished may QMX.? Everything checks out except the RF sweeps.?
The radio seems to work fine in all modes and passed all the diagnostics except the rf sweeps all look like noise and the level is low compared to the?
published sweeps in the manual.
Did I miss something running the test?
I'm considering re-winding T407 just as some path forward.??
I don't have the case installed in case that makes a difference.
Your thoughts are much appreciated.
Traces:
Kindest regards,
Tim W8TWF
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I just completed my 3rd QMX build, this being my first High-Band QMX. It is a 12 Volt 2023 Rev 2 board with 3 modifications done by me, the addition of the diode (surface mount) for potential parasitic oscillations, and the jumper for the PTT Out grounded functionality, and 3) replaced the power socket with a power cable with power-poles. It is running the _17 firmware with AGC enabled. Everything appears to work correctly and it appears to be receiving OK ... except that I'm getting about half the power out that I should be expecting. What should I be looking at that I may have done wrong, or that should be adjusted? What other tests can I perform to determine the issue? Here's my data while the QMX is connected to a QRP-Labs dummy load: It's drawing 212 mA powered up and idle, which is high! And it feels warm (I'll look at it w/ infra-red camera next). My low-band QMX draws around 93 mA at idle. When transmitting (CW key down) on: 20M drawing 716 mA 17M drawing 775 mA 15M drawing 833 mA 12M drawing 740 mA 11M drawing 760 mA 10M drawing 755 mA
Diagnostics Power Out into Dummy Load
12V power input
BIAS SMPS (during transmit)
30.4 mA Duty Cycle 14%
?
20M 2.4W 10.1V SWR 1.09
17M 2.5W 10.1V SWR 1.22
15M 2.2W 10.1V SWR 1.40
12M 1.7W 10.1V SWR 1.60
11M 1.6W 10.1V SWR 1.70
10M 1.6W 10.1V SWR 1.75
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Audio Filter Sweep
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RF Filter Sweep
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Low Pass Filter Sweep
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Image Sweep
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SWR Sweep (into QRP-Labs Dummy Load)
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-- 73 de Roy - KI0ER Littleton, Colorado USA
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Hi,
Is there any way to key the CW transmitter via CAT?
I experimented with sending "TQ1;" but it doesn't output any RF. I
simultaneously sent 50 Hz tone via the sound card interface and it does
output RF, but only in digi mode. In CW mode is doesn't seem to do
anything (but the mode, queried with "TQ;", is switched to 1 = TX).
What worked was:
- sending MD6; to switch to digi mode
- sending TQ1; to enable transmitter
- sending tone via sound card interface
- sending TQ0; to disable transmitter
- sending MD3; to switch to CW mode
It works, but:
- it looks very hacky to me (and I'm worried about timing stability,
but I didn't test it)
- frequency is different from the one emitted when I press the paddle
by the frequency I send via the sound card interface
- there's no audible sidetone
- probably there's also no envelope (I didn't test it -- does the QMX
apply envelope for signals transmitted in the digital mode? I doubt, but
maybe?)
Second point could probably be solved by sending "FA;" to read the VFO A
frequency, sending another FA to lower it by the frequency emitted via the
sound card interface (for example 1 kHz less, and emit 1 kHz to the sound
card), and then send another FA to increase it again when keying up, but
it's even more hacky this way.
Is there any other way to programatically send CW with QMX?
Alternatively: is there any way to use the paddle port for a paddle, with
QMX's keyer, and any other port (PTT port) as a straight key input? This
way I could do some hardware to just toggle PTT via another port.
Basically, what I need is to be able to transmit CW both from a PC and
from a paddle, at the same time. Before Saturday, as SP DX Contest is on
Saturday...
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Re: Something to look out for: possible cause of PA failure (QDX etc).
I think that bending the device lead without supporting it between the bend and the body was the cause of the cracked encapsulation.
Hold the lead close to the body with tweezers or fine needle-nosed pliers and use another tool to bend the lead.? Don't exert any force on the FET body.?
If you break the device open you will see that the lead does not protrude very far into the encapsulation, thus has limited strength.
Those solder blobs on the ground pad were caused by someone's tinned soldering iron touching the pad.
73, Don N2VGU
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Re: [QMX rev3 high band] Need help troubleshooting bad AF, RF and Image sweep results
Frank,
Proper 2.5V on those 4 pins is necessary but it is not sufficient to conclude the PCM1804 is OK. A number of internal failure modes appear to be possible, with varying consequences.
?A good next step would be to put the radio into IQ mode, connect it to a PC program which can show data independently from the I and Q channels, (like Audacity, HDSDR, there may be others). Tune in a strong carrier to produce an audio beat note, and compare the results? presented by the software.
What is going on with your TX power and T507? To me what you have described does not compute...
GL JZ KJ4A?
I have the same problem - bad AF, RF, image sweeps (10m-20m) on kit QMX rev 3.? I just checked the 4 voltages (VrefL, VrefR, VcomL, VcomR) on PCM1804, they are all in the neighborhood of 2.5V.? I did have problems earlier with T507 and was putting out almost 10W on 11.9V battery.? My bad.? I fixed and re-installed the T507.? Now I only get 1W-1.2W.? As I hold the "t" key down in the diagnostic mode in PuTTy the wattage decreases slowly.? Otherwise audio "sounds" great with dummy load and straight key.? AGC seems to work great too.
Any ideas for next step?
I spent several hours under a microscope looking for solder bridges and cleaning flux.? And checking for decent solder joints.? Checked all toroids installation for continuity, all this looks good.
Thanks!
Frank
K8FXG
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Re: [QMX rev3 high band] Need help troubleshooting bad AF, RF and Image sweep results
I have the same problem - bad AF, RF, image sweeps (10m-20m) on kit QMX rev 3.? I just checked the 4 voltages (VrefL, VrefR, VcomL, VcomR) on PCM1804, they are all in the neighborhood of 2.5V.? I did have problems earlier with T507 and was putting out almost 10W on 11.9V battery.? My bad.? I fixed and re-installed the T507.? Now I only get 1W-1.2W.? As I hold the "t" key down in the diagnostic mode in PuTTy the wattage decreases slowly.? Otherwise audio "sounds" great with dummy load and straight key.? AGC seems to work great too.
Any ideas for next step?
I spent several hours under a microscope looking for solder bridges and cleaning flux.? And checking for decent solder joints.? Checked all toroids installation for continuity, all this looks good.
Thanks!
Frank
K8FXG
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Antarctica on WSPR, attached.
--
- 73 de Andy -
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Tisha Hayes, AA4HA
Donald S Brant Jr
Frank G