Re: QMX article in the QST
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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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Shirley Dulcey KE1L