QMX+ Resistance measurements
Is there a chart of pre-power up resistance measurements?
Power socket is 15 Mohm
Antenna socket is 0.7 ohm
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Dan Reynolds -- KB9JLO
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The common PCM1808 module seems to have a high DOA rate also.? I am one of the T41 builders and have had 3 out of 5 DOA. Maybe the manufacturer isn¡¯t doing a great job testing, or the baddies are slipping out of the factory floor sweeps.?
Larry KB3CUF? On Wed, Jul 10, 2024 at 9:20?PM Kaufman, Matt - N3AR via <matt.d.kaufman= [email protected]> wrote:
I know that Hans is a (super) busy dude, but this really seems like something that he should want to dig into; the abnormally high number of "it must be this IC" has gotten?to the point where now, people are just assuming the chip went bad when things don't work and being right in their assumption.? Anecdotally, this seems like a platform issue of some sort since this one component seems to be such a common failure point.
On Wed, Jul 10, 2024 at 6:15?PM Michael N2ZDB via <n2zdb.radio= [email protected]> wrote: OK so the problem was a defective (maybe counterfeit?) PCM1804 IC.
Once this part was replaced (after purchasing from Mouser.Com) my receiver sprung to life:)
I am lucky I have the skills to replace this part myself.
The initial symptoms were once the QMX+ was turned on - I heard some noise that quickly faded out within a few seconds.
I figured from the beginning that I had a defective IC after hearing others with the same problems.
73's Michael N2ZDB
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Re: Issues with summer travel and hot cars?
On Wed, Jul 10, 2024 at 12:35 AM, Nolan K0HAA wrote:
Should I be concerned with leaving it in a hot car in a southern Utah summer
Consider that much of the electronics in your car are powered on and exposed to temperature extremes 24/7/365, and can be expected to survive for decades. Heat is not great for batteries, though it won't kill them. A couple of hours in a parked car should be a walk in the park for your radios.? I would not leave LCD displays in direct sunlight, though.?? 73, Don N2VGU
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Re: FS: QMX Low Band, With Enclosure
Jim Bennett
I would really use the low band QMX
Fair price
How do we proceed? Paul Wamble 214-405-5876, iPhone?
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On Jul 10, 2024, at 5:42?PM, Jim Bennett / K7TXA via groups.io <w6jhb@...> wrote:
?Dang it - forgot to mention - it is wired for 12 volt operation.
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Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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I know that Hans is a (super) busy dude, but this really seems like something that he should want to dig into; the abnormally high number of "it must be this IC" has gotten?to the point where now, people are just assuming the chip went bad when things don't work and being right in their assumption.? Anecdotally, this seems like a platform issue of some sort since this one component seems to be such a common failure point.
On Wed, Jul 10, 2024 at 6:15?PM Michael N2ZDB via <n2zdb.radio= [email protected]> wrote: OK so the problem was a defective (maybe counterfeit?) PCM1804 IC.
Once this part was replaced (after purchasing from Mouser.Com) my receiver sprung to life:)
I am lucky I have the skills to replace this part myself.
The initial symptoms were once the QMX+ was turned on - I heard some noise that quickly faded out within a few seconds.
I figured from the beginning that I had a defective IC after hearing others with the same problems.
73's Michael N2ZDB
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OK so the problem was a defective (maybe counterfeit?) PCM1804 IC.
Once this part was replaced (after purchasing from Mouser.Com) my receiver sprung to life:)
I am lucky I have the skills to replace this part myself.
The initial symptoms were once the QMX+ was turned on - I heard some noise that quickly faded out within a few seconds.
I figured from the beginning that I had a defective IC after hearing others with the same problems.
73's Michael N2ZDB
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Very happy to report that the PCM1804 replacement fixed my problem.?
That is the most challenging chip that I have ever replaced.? I had a solder bridge between two of the little leads that just refused to come out.??
I have to admit that I am a great fan of ChipQuik.? Great stuff.
So far, I have only done receive.? I want to optimize the filters before I move on to transmit, but I did attach the QMX+ to an old tribander antenna, and I picked up Nepal at -18.? I am very impresseed!
Mark
W8GU
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Re: My QMX+ has a .3 ohm short on VDD
Dear Gregg.
I am slowly crawling out of the abyss.... my front panel doesn't light up .... yet????? I can get it to come up a little bit for about 3 minutes... I got putty up and tried to look at the diagnostics.? I can get just one page...? I was able to check out all the buttons and they were good..? the readings on voltages doesn't match my metter readings of Vdd and Vcc. ? but it is reading them.... but other than that it doesn't tell me much... but at least I have made some progress.? I can see a dark row of blocks on the top of the screen sometimes... but no backlight operation yet.??
Here is the diagnostics page I was able to get and copy:
tomorrow is another day..... still trying to figure out what this means...
take care and have fun...
73 Dave WA5DJJ
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Re: QLG2 GPS Interface With QCX, QMX
Will do, Greg.
Being the impatient type, I decided to try WSPR by manually setting the time.? I made a run on 30 meters, and it worked well.? Even heard by three stations in Australia.? The map is attached.
Now, back to working on the GPS !
73,
- Bill? W3WJ
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Re: FS: QMX Low Band, With Enclosure
Dang it - forgot to mention - it is wired for 12 volt operation.
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Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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FS: QMX Low Band, With Enclosure
Hi All - last month I listed and sold a QMX high band rig and a QMX low band rig. Well, it turns out that I actually had two of the low band units here. Now that I have an operational mid band unit AND a QMX+, I've no need for that additional QMX Low Band radio. So, I'm offering it for sale at $120. It works very well and is in pristine condition. I just connected it to my computer with PuTTY and here are the wattage output measurements from the QRP Labs utility:
80 - 4.4 watts
60 - 4.5 watts
40 - 4.6 watts
30 - 4.3 watts
20 - 4.7 watts
It includes the QRP Labs black enclosure, AND a third party 3D printed pair of "legs" that can be snapped on the sides to elevate the QMX off your desk an inch or so at an angle that makes viewing a lot easier than lying flat. They were only about $6, but they make using the radio on your desk "more better".
Free shipping to any US address. PayPal friends and family to my K7TXA AT ARRL DOT NET address, or mail me a check/cash to my QRZ address. Please let me know offline if you are interested.
Thanks, Jim
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Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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Re: AA Batteries and QMX+: is it safe to use?
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Re: QLG2 GPS Interface With QCX, QMX
Pay it forward :)?
Have fun.?
On Wed, Jul 10, 2024 at 5:28 PM, Bill Jobes via groups.io <jobes@...> wrote: Thanks very much, Greg !? ?That's excellent into.
- Bill
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Re: QLG2 GPS Interface With QCX, QMX
Thank you, Alan !
- Bill??
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Re: When 200 Hz is too wide
Brent
Maybe but it may mean changing a lot of capacitors.?
Please note the bandwidth is only part of the picture. One must also consider the shape and degree of its rejection. A smaller bandwidth at the 3 dB points might have very little difference at say the 40 and 50 dB points? also reducing bandwidth may add distortion to the signal.?
With a suitable audio dsp program like spectrogram you can observe the shape of the filter by just receiving noise. The stock qcx isn't bad.??
Curr
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Re: QLG2 GPS Interface With QCX, QMX
Thanks very much, Greg !? ?That's excellent into.
- Bill
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Re: Issues with summer travel and hot cars?
Thanks for the heads up, I never thought of that but you¡¯re right, batteries are probably the bigger issue here.?
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Re: AA Batteries and QMX+: is it safe to use?
On Wed, Jul 10, 2024 at 03:34 PM, Andrew wrote:
However, the output voltage is 12.9 volts.
Check the voltage actually getting to the PC board (not at the battery) when the radio is receiving and when transmitting into a dummy load. I suspect you will find that it drops to a safe level when transmitting, which is when it most important for the finals' safety. This is due to wire and contact resistance and internal resistance of alkaline batteries.? Rechargeables tend to not drop their voltage as much so check before transmitting into an imperfect load. Too high for comfort?? Put in a dummy cell or a couple of diodes (maybe switchable) and lower the voltage that way. A little higher than 12?? Probably OK but the risk rises with VSWR and voltage, so you are in test pilot territory. Don't say Hans didn't tell you so! 73, Don N2VGU
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Re: AA Batteries and QMX+: is it safe to use?
Using NiMH cells will reduce the output voltage.? Tho fully charged NiMH cells do have a higher than1.2VDC / cell.
Replace one (or two) of the AA cells with a 'dummy' cell - both will offer a lower voltage.?
I happen to use a 10xAA cell battery pack for my portable rigs.? Use a voltmeter to determine what is the actual battery voltage before use.
Good luck.
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Hi All,
I have just finished the build on the QMX+ Very pleased with it and have made several contacts on FT8. However the O/P power is low on higher bands:
160m 5.0W
80m? 4.1W
40m? 3.2W
30m? 3.4W
20m? 3.2W
17m? 3.6W
15m? 3.4W
12m? 2.5W
10m? 1.8W
6m??? 0.9W
I would be happy with 3-5W but 0.9W on 6m is a bit low as my main interest is the higher bands which was the main reason for buying the QMX+. I already have a QDX which performs nicely..
Does anybody have any suggestions why the output may be so low on 10m & 6m?
BTW the power output was measured with a Marconi Power meter and correlates well with the QMX+ figures...
Thanks in advance for any sugestions
73 de Dave G4FAW
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Dan Reynolds
Donald S Brant Jr
Paul K5EBP
Kaufman, Matt - N3AR
Michael N2ZDB