Re: QDX rev 6 image freq problem
If the problem occasionally changes:
Try applying heat, cold, and mechanical pressure, this might localize the problem.
Perhaps flex the board a bit (but not too much!), this might show if it's a bad solder joint or open trace.
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Jerry, KE7ER
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On Mon, Oct 14, 2024 at 04:09 AM, Fredrik (OH1HSN) wrote:
Frustratingly, once while testing I got a good result on the image rejection test, then it got back to the old behavior of no image rejection and the left channel being silent.
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Remove the GPS module if you installed it.? My power jumper under it was too big and it grounded out on the GPS antenna connector.? I had the exact same symptoms.? It came to life when I removed it.? I have fixed my jumper.
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Re: QMX article in the QST
Maybe Rob Sherwood will eventually take a look at the QMX+.
--
John AE5X
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Re: Sending prosigns via CAT KY
Hello Andreas
Agreed, these? would? both be useful items. I have added them to my development list for the next firmware version.?
On Sat, Oct 12, 2024 at 5:40?PM Andreas DM7AK via <mail2dm7ak= [email protected]> wrote: Dear Hans,
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In case you get stuck with NF audio chain for SSB and need some low hanging fruit distraction - the KY CAT command is lacking a way to send prosigns.
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How about an underscore prefix as with the message memory?
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And - after I had an incident where another station just broke into my transmission and did not realize that the qrg is busy - I wonder how it could be made possible to interrupt a lengthy ongoing? transmission by insta-flushing the tx buffer, e.g. on long press of menu button.
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73, Andreas
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Re: QDX rev 6 image freq problem
Thanks Oleh! I'm quite confident my problem is further in the chain, as I see nice I and Q signals after the audio amplifiers = at the inputs of the ADC (attached screenshot, measured over the capacitors after the OpAmps)
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Thanks Jerry and all for the magnification and soldering advice!
I have a desk lamp with magnifying glass to solder under, and I also have an USB microscope. I agree, the USB microscope has some issues. For me mainly that I cannot work well under it, as there is little space. Also there is a bit of lag in the image, making my hands feel strangely heavy when I move a tool under the microscope. It seems it's time to start looking for a binocular microscope. This time, I've used the USB microscope to inspect the soldering.
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To return to the image rejection issue.
I've measured the ADC chip pins with an oscilloscope and found this:
- the reference and common pins all have a good-looking voltage near 2.5V, same between left and right channel
- there is a good audio signal on each Vin
- simultaneously measuring LRCK and data out, there is data in the right channel but only zeros in the left. (attached image, red is LRCK, yellow is data. Don't mind the amplitudes, scales are different and one of the probes was on 10x accidentally)
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Frustratingly, once while testing I got a good result on the image rejection test, then it got back to the old behavior of no image rejection and the left channel being silent.
This feels like a loose pin sometimes making contact. But the measurements above make me think the ADC chip is broken. I did try to reheat the chip pins associated with the left channel, with no change.
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I think I'm stuck here, unless I start replacing the ADC chip. Not expensive but I'm not 100% confident I can solder it... and the radio is decently usable? as it is.
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@Ron the original author: sorry for hijacking the thread. I don't know if you have the same problem as me. I'd suggest one way to find out is to measure the audio signal
after theOp Amps with an oscilloscope, with a signal source attached. If you loose one of the channels earlier in the circuit like Oleh, you would see it there.
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Best,
Fredrik
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I had same simptoms recently.
Pull out smps, measure vdd to gnd resistance if around 2ohms thats bad, you have a short
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Measure ESR of tantals on vdd line of PCM1804 if any of the two shows over 60 ohms welcome to the club, you have shorted PCM IC,
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Unsolder it and order new ones
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Like I said !
Bruce says "¶Ù´Ç²Ô¡¯³Ù get the pre programmed ones"
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Re: Clear SWR Protection "S" through the USB port?
Hans,
It is wonderful to be associated with an OUTSTANDING vendor.
You guys are the BEST!
On Mon, Oct 14, 2024 at 1:33?AM Hans Summers via <hans.summers= [email protected]> wrote: Hi Sam
It's good that there's a workaround however, I think it would be tidy for there to be a CAT command which returns the SWR protection (and other kinds of protection, like battery voltage) status and lets you clear it via a command. So I have added this to my list.?
I have QMX+ bundled with a mini PC and I connect via remote desktop to run WSJT-X, etc.
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I have been using this setup with my QMX successfully for a few months.? It works well with my ATU-10 and Ultimax100 antenna .
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The QMX+ however, has gone into SWR Protection a few times.? And with the rig in another room, I would like to be able to reset the "S" remotely.
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Through the terminal connection, perhaps?
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Is that possible?
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Any info/advice appreciated .
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Tanks,
Sam Hanie, AC4OW
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Re: QMX article in the QST
SDRs are notoriously difficult to measure with conventional lab techniques, so it's possible the ARRL Lab got it wrong. I'm pretty sure they DID get that blocking gain compression number wrong.
Yes, I thought about that too. I used to scoff at the "excuses" that conventional measurement techniques of some performance characteristics don't work properly on SDRs compared to analog transceivers. But now I understand why it is so.?
The main body of the review text did not make any mention of the fact that the QMX is an embedded SDR transceiver. so it's also possible that the ARRL lab did not realize that it's an SDR and that they should handle it differently in their testing ? It's also true that the dynamic range numbers for the QMX are held back by its relatively poor MDS compared to the big name rigs. But those low MDS numbers for the big name rigs are largely useless; the QMX can hear down to the band noise floor under most conditions. 10 and 6 meters in a quiet location might be an exception, and you might also need better weak signal performance if you're using a lossy receive antenna (flag, Beverage, etc). That sensitivity, though, does give you room to use attenuation and handle even stronger signals.
Worth noting also that the QMX+ and latest QMX PCB revisions use the LT6231 op-amps instead of LM4562. The LT6231 has a 1.1 nV / sqrt(Hz) input noise compared to 2.7 for the LM4562. So while the LM4562 is an excellent op-amp the LT6231 is about the best you can get (and priced accordingly!). I did determine by measurement that the LT6231 gives about an 8dB increase in sensitivity (which is expected by the improvement in input noise); and about a 6dB dynamic range improvement compared to the LM4562.?
The ARRL lab measurements were done on an older QMX so it had the LM4562 op-amps. Had they had the latest one with LT6231 it would have given another 8dB sensitivity.?
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Thanks for the pointers. I initi6had the current limit set to around 100mA and then increased it to 500mA, but still no joy.
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Stans explanation of what this component is doing is very useful, I will take a look at his suggestions, I now have something to investigate.
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Re: QMX article in the QST
SDRs are notoriously difficult to measure with conventional lab techniques, so it's possible the ARRL Lab got it wrong. I'm pretty sure they DID get that blocking gain compression number wrong.
It's also true that the dynamic range numbers for the QMX are held back by its relatively poor MDS compared to the big name rigs. But those low MDS numbers for the big name rigs are largely useless; the QMX can hear down to the band noise floor under most conditions. 10 and 6 meters in a quiet location might be an exception, and you might also need better weak signal performance if you're using a lossy receive antenna (flag, Beverage, etc). That sensitivity, though, does give you room to use attenuation and handle even stronger signals.
As for me, I'm quite happy with my?QMX. Though if I ever feel masochistic enough to have a go at Sweepstakes I might choose another rig.
On Sun, Oct 13, 2024 at 11:46?PM Hans Summers via <hans.summers= [email protected]> wrote: Hello Shirley, Steve
In my opinion the QMX should show considerably better strong signal performance than reported in the QST review. If you compare it with the QCX review for example, the QCX review in QST (on the QCX page) has better numbers. But this should not be the case, QMX has a higher performance receiver than QCX. I have made a lot of measurements of my own that demonstrate this. I suspect there might either be something wrong with the ARRL's specific setup and procedure for this review, or some issue with the unit they tested. Still - it is what it is and anyway the rest of the review is extremely positive, as Shirley said, keying characteristics, fast turnaround; and the very low receive latency.
73 Hans G0UPL
To put those numbers in perspective: the QMX doesn't have the strong signal performance of a state of the art 2024 design, nor should we expect it to at its price point. Aside from the number for blocking gain compression, which is likely caused by AGC action rather than blocking in the front end, those numbers would have been respectable for a high end rig in 1994. They're still good enough to make using the QMX on the air a pleasant experience in anything but the busiest contest conditions,?and better than we'll see from most rigs that?cost under $1,000. The excellent numbers for transmit keying sidebands are also worthy of note, and the fast T/R turnaround means that it will work well for full QSK. The CW keying waveforms are also outstanding; no shortening of the first dit, and both of the dits on the scope trace are the correct length.
On Sun, Oct 13, 2024 at 6:37?PM Steven Dick, K1RF via <sbdick= [email protected]> wrote: Thanks - colors did not reproduce correctly in the specs on the left side of P38. Here's a version with correct colors.
-Steve K1RF
------ Original Message ------
Date 10/13/2024 5:53:04 PM
Subject Re: [QRPLabs] QMX article in the QST
Here's a fair use copy of the review only:
?
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Re: Clear SWR Protection "S" through the USB port?
Hi Sam
It's good that there's a workaround however, I think it would be tidy for there to be a CAT command which returns the SWR protection (and other kinds of protection, like battery voltage) status and lets you clear it via a command. So I have added this to my list.?
I have QMX+ bundled with a mini PC and I connect via remote desktop to run WSJT-X, etc.
?
I have been using this setup with my QMX successfully for a few months.? It works well with my ATU-10 and Ultimax100 antenna .
?
The QMX+ however, has gone into SWR Protection a few times.? And with the rig in another room, I would like to be able to reset the "S" remotely.
?
Through the terminal connection, perhaps?
?
Is that possible?
?
Any info/advice appreciated .
?
Tanks,
Sam Hanie, AC4OW
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The factory pre-programmed versions of the Si5351A are often not suitable because they have a different I2C address as well as default registers values wer up for specific output frequencies.?
Digikey, Mouser, Arrow etc should not be selling these factory pre-programmed versions, normally falsely associating them with the standard datasheet which does not apply in totality (such as different I2C address, non zero default register contents at powee-up). I did inform them years ago, but of course they continued selling then. I suspect it has misled many unsuspecting purchasers. They below with other fell-off-the-back-of-a-lorry junk on eBay or surplus stores, not misrepresented by major reputable distributors.?
So: never try to use Si5351A_Bnnnnn_ ... types. Stick to Si5351A_B_GT (or GTR). Or MS5351M (as far as I'm aware MS5351M isn't sold in factory pre-programmed versions anyway).?
73 Hans G0UPL
Good to know.? Thanks!
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On Sun, Oct 13, 2024 at 03:42 PM, Ronald Taylor wrote:
Hi All. Back in 2020 I mistakenly ordered a Si5351 that was pre-programmed for a fixed frequency and it did not work in a QCX I was repairing. I had to order the correct one that was not programmed. Since then I've only used the un-programmed versions, both Si and MS5351 depending on what was available.
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Those output powers you listed, are very close to my QMX+ build as well. ?Looks normal to me. ?I've worked the world on this rig already!
VE7SRF
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Re: QMX article in the QST
Hello Shirley, Steve
In my opinion the QMX should show considerably better strong signal performance than reported in the QST review. If you compare it with the QCX review for example, the QCX review in QST (on the QCX page) has better numbers. But this should not be the case, QMX has a higher performance receiver than QCX. I have made a lot of measurements of my own that demonstrate this. I suspect there might either be something wrong with the ARRL's specific setup and procedure for this review, or some issue with the unit they tested. Still - it is what it is and anyway the rest of the review is extremely positive, as Shirley said, keying characteristics, fast turnaround; and the very low receive latency.
73 Hans G0UPL
To put those numbers in perspective: the QMX doesn't have the strong signal performance of a state of the art 2024 design, nor should we expect it to at its price point. Aside from the number for blocking gain compression, which is likely caused by AGC action rather than blocking in the front end, those numbers would have been respectable for a high end rig in 1994. They're still good enough to make using the QMX on the air a pleasant experience in anything but the busiest contest conditions,?and better than we'll see from most rigs that?cost under $1,000. The excellent numbers for transmit keying sidebands are also worthy of note, and the fast T/R turnaround means that it will work well for full QSK. The CW keying waveforms are also outstanding; no shortening of the first dit, and both of the dits on the scope trace are the correct length.
On Sun, Oct 13, 2024 at 6:37?PM Steven Dick, K1RF via <sbdick= [email protected]> wrote: Thanks - colors did not reproduce correctly in the specs on the left side of P38. Here's a version with correct colors.
-Steve K1RF
------ Original Message ------
Date 10/13/2024 5:53:04 PM
Subject Re: [QRPLabs] QMX article in the QST
Here's a fair use copy of the review only:
?
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Re: QMX article in the QST
To put those numbers in perspective: the QMX doesn't have the strong signal performance of a state of the art 2024 design, nor should we expect it to at its price point. Aside from the number for blocking gain compression, which is likely caused by AGC action rather than blocking in the front end, those numbers would have been respectable for a high end rig in 1994. They're still good enough to make using the QMX on the air a pleasant experience in anything but the busiest contest conditions,?and better than we'll see from most rigs that?cost under $1,000. The excellent numbers for transmit keying sidebands are also worthy of note, and the fast T/R turnaround means that it will work well for full QSK. The CW keying waveforms are also outstanding; no shortening of the first dit, and both of the dits on the scope trace are the correct length.
On Sun, Oct 13, 2024 at 6:37?PM Steven Dick, K1RF via <sbdick= [email protected]> wrote: Thanks - colors did not reproduce correctly in the specs on the left side of P38. Here's a version with correct colors.
-Steve K1RF
------ Original Message ------
Date 10/13/2024 5:53:04 PM
Subject Re: [QRPLabs] QMX article in the QST
Here's a fair use copy of the review only:
?
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Re: Why not provide a MP3 of an actual MCX+?
Same here, it all personal preference and some amount of how I use it.
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My favorite RX is still the QCX with the audio filter modded for SSB
(Hipass 250hz, LOpass2400hz).? And a lot of close seconds.
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--
Allison
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Post online only,?
direct email will go to a bit bucket.
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Re: QDX: Troubleshooting high output power
Please note that the bandpass filters are only for receive, so they shouldn't be affecting your transmit.? The low pass filters, along with the two binocular toroids are in the transmitter path - check them carefully.?
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Re: Why not provide a MP3 of an actual MCX+?
Also before someone gets triggered I was having a bit of fun here. There are gross generalizations, biased opinions, and otherwise non objective feedback included in my last post. Mixed with a few facts about how Hans did indeed do great things to preserve quality in the RX path.?
please. Sleep well tonight, even if we disagree.?
i am also not implying that money in any amount makes one¡¯s training relevant ?. I don¡¯t work in audio at all now, nor do I have a stack of accolades next to my name in that arena. Again some fun.?
but I have heard some great audio in my lifetime, and some of it came from my qmx.?
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Re: Why not provide a MP3 of an actual MCX+?
The QMX doesn't have a speaker, and how good the sound is will also depend highly on the speaker you use.? I agree with those that have praised the QMX audio, but have also heard it be raspy and annoying when I use the wrong earbuds, or when the volume is too high for the particular speaker attached.
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Tom WE8TOM
Fredrik (OH1HSN)
Ivica - YU1QRP
Bruce Akhurst
Sam Hanie
Shirley Dulcey KE1L