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Hello,
?
you will find a very positive five page review of the "QRP Labs QMX 5W QRP Transceiver" in the November issue of the QST. It covers the firmware version 15 and the usual measurements are included. So it is not only Hans, who tells how good the QMX is. The numbers support his arguments, but puts again some pressure concerning the SSB part on Hans.
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To add some pressure ;-) : I was looking for the CW-Machine called "QRP Labs QMX 5W QRP Transceiver"... I know, I know ...?
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Hajo
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Here's a fair use copy of the review only:
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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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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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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:
?
|
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:
?
|
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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Maybe Rob Sherwood will eventually take a look at the QMX+.
--
John AE5X
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You should send one here to get
tested?
Joe WB9SBD
On 10/13/2024 10:46 PM, Hans Summers
wrote:
toggle quoted message
Show quoted text
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:
?
|
HELLO!? Is the LT6231 a "drop-in" replacement for the legacy op amp? If not, can the QMX hardware be modified to accommodate this upgrade?
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Kindest regards, John, W9NET??
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Curious, why would you think that is an upgrade?
And the LT6231 is a single op-amp device, and the current devices on the QMX are dual op-amps, so no, it is not a drop-in replacement.
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LTC6230 is single? LTC6232 is dual and LTC6232 is quad.?
73 Ross
toggle quoted message
Show quoted text
On 15 Oct 2024, at 17:52, Stan Dye <standye@...> wrote:
? Curious, why would you think that is an upgrade?
And the LT6231 is a single op-amp device, and the current devices on the QMX are dual op-amps, so no, it is not a drop-in replacement.
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On 15/10/2024 17:42, Pinball Wizard via groups.io wrote: Is the LT6231 a "drop-in" replacement for the legacy op amp? If not, can the QMX hardware be modified to accommodate this upgrade? John, Is the LT6231 a "drop-in" replacement for the legacy op amp? If not, can the QMX hardware be modified to accommodate this upgrade? /g/QRPLabs/message/131334You can finish that by comparing the schematics, I do not think there is a difference. 73 Alan G4ZFQ
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LT6231 is a dual opamp, see the datasheet.
Curious, why would you think that is an upgrade?
And the LT6231 is a single op-amp device, and the current devices on the QMX are dual op-amps, so no, it is not a drop-in replacement.
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Hi John
LT6231 is a dual op-amp and a drop-in replacement for the LM4562 with no other circuit changes.?
73 Hans G0UPL
On Tue, Oct 15, 2024, 20:42 Pinball Wizard via <jlittlejohnmd= [email protected]> wrote: HELLO!? Is the LT6231 a "drop-in" replacement for the legacy op amp? If not, can the QMX hardware be modified to accommodate this upgrade?
?
Kindest regards, John, W9NET??
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Thanks everyone for your thoughts. Changing the dual op amp and getting 8 dB more sensitivity and decreased noise seems like a valid improvement to me.??
Regards, John W9NET
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Thanks everyone for your thoughts. Changing the dual op amp and getting 8 dB more sensitivity and decreased noise seems like a valid improvement to me.??
Yes, certainly it is not a bad thing :-)? But as Shirley KE1L said, most of the time particularly on the lower bands, the band noise or local QRM is much higher than the receiver noise floor anyway so making the receiver quieter doesn't help. For higher bands and in very quiet locations, in some circumstances the higher sensitivity can be useful.
73 Hans G0UPL
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On 16/10/2024 06:36, Pinball Wizard via groups.io wrote: getting 8 dB more sensitivity and decreased noise Actually more sensitivity is achieved by having less internally generated noise. As others have said if you hear antenna noise then lower RX noise will make no improvement. 73 Alan G4ZFQ
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Catching up on my groups.io and saw this thread:
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As the person who write the QST review, I can confirm I have an original QMX from the first lot at Hamvention. I was not involved with the labs testing and have no idea on which one they were using. I do know it took them a while to test as I submitted my review around the time of Hamcation.?
I stand by the review and love the QMX. I appreciate the additional firmware upgrades and wish I could have updated the review. The QMX is a fantastic kit and it is my goto POTA radio.?
that said I¡¯m working on the QMX+ review right now. Spoiler alert: another fantastic kit, but I do wish the form factor was a little different. It hasn¡¯t replaced the QMX as my main POTA?rig, even with the additional bands, mainly because it¡¯s just slightly too big to travel with.?
Im not sure it¡¯s the op amps or maybe I¡¯m just always using it my home antenna, but I do seem to get slightly better performance out of it compared to the QMX. Regardless, fun builds and great radios!
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As the person who write the QST review, I can confirm I have an original QMX from the first lot at Hamvention. I was not involved with the labs testing and have no idea on which one they were using. I do know it took them a while to test as I submitted my review around the time of Hamcation.?
I stand by the review and love the QMX. I appreciate the additional firmware upgrades and wish I could have updated the review. The QMX is a fantastic kit and it is my goto POTA radio.?
It was a nice review, no problem with the review text; I think the lab might have got a couple of things wrong, but these things?happen. And there's always features or planned features which weren't mentioned, which one might argue should have been, but these are minor details and anyway when a radio like QMX is software-defined, with a lot of development still going on and some delay from review submission until publication, I think these things are normal.?? ? that said I¡¯m working on the QMX+ review right now. Spoiler alert: another fantastic kit, but I do wish the form factor was a little different. It hasn¡¯t replaced the QMX as my main POTA?rig, even with the additional bands, mainly because it¡¯s just slightly too big to travel with.?
Form factor is *supposed* to be a bit different! One for the road, one for the lab. QMX+ with double the number of bands and a few other extras; and easier to build, space to modify etc (witness the recent pile of battery/ATU project participants!).?? ? Im not sure it¡¯s the op amps or maybe I¡¯m just always using it my home antenna, but I do seem to get slightly better performance out of it compared to the QMX. Regardless, fun builds and great radios!
The LT6231 is now used in QMX as well as QMX+, I forget which PCB revision it started in. Wasn't in the first. So that makes some difference; also the QMX+ has in some bands better performance due to the fact that in QMX+ each BPF toroid is only single-tapped; one BPF toroid is shared between two bands; whereas on QMX you have one T50-2 for all the bands. So this makes a small difference too.?
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Hajo Dezelski
Randy K7RAN
Shirley Dulcey KE1L