I think I need to explain my proposal a little bit further to avoid
misunderstanding. I attach a PDF outlining the present design and my
alternative.
In the present design a BANDPASS filter is used, nominally with a center
around the sidetone frequency of 700 Hz. In my sketch it also includes
the Hilbert transform. I guess that the present filter is of order 10 or
so according to the graphs in the manual.
My proposal is to use ZERO BEAT of the received signal and use a LOWPASS
filter. To get similar performance as above, two filters (for I and Q)
of order 5 or so will be needed. The side tone is mixed after the filter
just in front of the DAC feeding the speaker/phones. An optional offset
(OF) can be added to adjust the center of the CW filter up and down.
This will mean two settings: bandwidth and center. These can be adjusted
independently.
The Goertzel algorithm can be replaced by an moving average to feed the
CW decoder.
Yours is a proposal for a radical redesign of the CW filtering, not just a change to the way the UI works.?
I don't think your proposal would work well, though I find myself lacking a deep enough understanding to explain why clearly. Perhaps someone else could contribute here also. But I'll try.
You say that we can get rid of the Hilbert transform - I don't see how that is the case. You need the Hilbert Transform, for image rejection at the IF.?
But if you consider abolishing the IF completely and doing everything at baseband, then I think what you are really proposing is Weaver method SSB reception - see my old analog page about this here (written 2014). This does indeed avoid the Hilbert Transform (at least explicitly, though the same is effectively achieved mathematically by the second mixing operation at the sub-carrier), and now you implement two low pass filters, each with half the desired bandwidth, and then finally a sub-carrier oscillator and mixer, which in this case would occur at the CW center frequency.?
Weaver demodulation is used in some SDRs. A disadvantage is that there is a hole in the response at the sub-carrier frequency (the CW sidetone frequency, in your nomenclature). In the analog world it is hard to make the hole small but in DSP it could be made a lot smaller, such that it is unobtrusive on an SSB receiver. However for CW, I wonder how that would work... the "hole" would be exactly at the center of the passband, and the CW transmission could well have energy either side of it, and given that the actual bandwidth of a CW transmission?could be only 10 or 20 Hz, even a small "hole" would have a marked effect.?
An additional problem is that you lose the advantage of doing the SDR at a 12 kHz IF. The 12 kHz IF gives immunity to hum and noise which can often be found on a direct conversion receiver near to (or within a few kHz of) 0 Hz. Operating at a 12 kHz IF produces significant advantages. The conversion to 12 kHz IF is quite trivial digitally and computationally inexpensive because the sampling is at 4x this (48 ksps).?
Finally another problem. To obtain a 50 Hz bandwidth CW filter, you would need to have a 25 Hz LPF. To do such a low pass filter in DSP will require a very long (large number of taps) DSP filter. To avoid this, it will be necessary to decimate down to a much lower sample rate. Which is fine. But you cannot avoid the fact that there will be a large delay through the filter. Intuitively and/or approximately speaking the filter must be 40 ms long for a 25 Hz LPF. That is a very large latency for a CW operator and prevents the use of QSK (full break-in). In reality this 40 ms is just the delay of the selectivity filtering, the actual receive latency would be even longer than that because you still have to do the conversion from analog to digital (ADC) and back to analog (DAC), as well as the decimation to lower sample rate which also involves a DSP transform. Then you will want to put in some AGC which is another delay line etc etc.?
In contrast if a filter is made by the superposition of two 500 Hz bandwidth filters, the bandwidth will still be 50 Hz but now the processing delay due to the?bandpass filter is 10x smaller, only 4 ms.?
So for a number of reasons I think that your proposal would work (it is just Weaver method SSB demodulation), but I think for CW it would be an inferior performance solution.
73 Hans G0UPL
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Hello Bill
Thanks for the feedback. I would love to hear from Braden too. When not liking the way something works, one should be able to propose an improved alternative.? ? From the user perspective,
I've found most other radios have you set your preferred CW tone/offset
(500hz, 600hz, 700hz, etc.), then choose a bandwidth around that tone.?
The QMX+ however presents you with a list of bandwidths that can be used with
several CW tones, then you must either live with the bandwidths that are
available for your chosen offset, or choose an offset based on the bandwidths
you'd like to use.?
Is it possible
to?change?the CW filter set up so that you can simply choose your
offset, then choose the bandwidth?? Or, stated differently,?can the
CW filters be made so that every bandwidth applies to every
offset/tone?
Yes this is exactly the?desired end goal. The reason it is the way it is now, is because way back there was just the 300 Hz filter. In the original way I had the code set up, there was just this single filter. It was suggested that two offset overlapping versions of the same filter could be used and that would provide a narrower bandwidth without causing ringing and increases in delay.?
As it happened I already had on hand from way way back, 10 years ago, I can't even remember where from, sets of filter coefficients for a bunch of other filter centers and widths. It was a small amount of effort to code this, and I released it in firmware 1_00_024 on 6-Aug-2024. At that time I had already begun my main 9 month project of implementing SSB in QMX, which so so many people have been waiting for, and I did not want to spend a large amount of time redesigning audio code. I wanted to stick to minor changes where possible. This implementation of the two overlapping filters was a low effort thing but provided great benefit to CW operators. But it isn't ideal, I know. It was intended as a temporary measure, with better ways to be implemented post SSB.?
73 Hans G0UPL
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Hi all,
I'm a new ham trying to build a power supply cable like this for my QDX or QMX+ to use my existing battery in the field:
?
> 18AWG cable w/ ring terminals > inline home-brew buck converter > 18AWG cable > fuse (1.5A?) > 18AWG cable > 2.1mm barrel connector
?
The part in bold is what I'm having trouble finding an obvious solution for. Is there a way hams typically build such fused cables without a whole lot of extra splicing? I feel like I'm missing something because I don't see much discussion about this or any pre-made assemblies like that. Sources for such an assembly would also be appreciated.
?
I saw this thread but ordering from UK to US and cutting off the Powerpoles isn't a good option.
?
Here's some we're doing if anyone's interested in that.
?
Thanks, Mike
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Hans,
????
Since you asked...
Note: For this discussion,
I interchange the terms CW offset and CW tone...sorry purists.
From the user perspective,
I've found most other radios have you set your preferred CW tone/offset
(500hz, 600hz, 700hz, etc.), then choose a bandwidth around that tone.?
The QMX+ however presents you with a list of bandwidths that can be used with
several CW tones, then you must either live with the bandwidths that are
available for your chosen offset, or choose an offset based on the bandwidths
you'd like to use.?
Is it possible
to?change?the CW filter set up so that you can simply choose your
offset, then choose the bandwidth?? Or, stated differently,?can the
CW filters be made so that every bandwidth applies to every
offset/tone?
?
Bill
W2EB
East
Syracuse, NY
toggle quoted message
Show quoted text
Hello Braden
What would be a simpler way of arranging it? I can alter
it...?
On Wed, Apr 9, 2025 at 3:29?PM Braden Glett
via <bradenglett= [email protected]>
wrote:
N2DI's video helps a lot, but overall my comment would be that the filter
system is just needlessly complicated, at least from a CW operator
perspective. Not sure about SSB or digital.?
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Marek, I guess now there are three possible places for a fault:
- LCD module
- Contakt from controller I/O via the mainboard to the connector
- somewhere an unwanted contact / resistance only in presence of some voltage
And I think No 1 with the highest possibility but who knows.
?
73 Ludwig
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Re: QMX+ with 100 amp/hour lithium iron battery
The 78/79 hundred families of regulators expect bypassing on both input and output sides of the regulator.Look at the data sheet for recommended values. Typically, 3.3uf and 0.1 or 0.01uf on the output. Short lead lengths are also recommended. without these, stray inductance is going to cause the regulators to oscillate.
Rick K8BMA
?
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Winlink and VARA HF setup for QMX
I would be grateful if smb can explain in detail what I need to do send e-mails threw QMX. I have no experience with Winlink and limited experience with FT8 data transfer. I have tablet PC (Win 8) with VARA HF and Winlink Express installed and I have QMX. What I need to do to set all these properly??
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Re: Here's hoping for QMX+ v2
Works great (mini PC):
--
John AE5X
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Re: Here's hoping for QMX+ v2
On Thu, Apr 10, 2025 at 09:18 AM, Jerry Gaffke wrote:
May be possible to do all you want by adding an RPi-Zero and a screen of your
choice into the top half of the QMX+ clamshell.
Hans plans to add more firmware features to the QMX, allowing more control via
UART and USB.
Jerry, this is an idea that has been floating around in my head. Some folks like the UI of the TR-45 or the K2. With CAT (and eventually BASIC scripting), those UI's and most of their features could likely be replicated with an RPi-Zero talking to the QMX. And, as Samantha suggests, the zBitx. Separating out RF design and UI design seems like an opportunity. 73 de Todd W2TEF
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Re: QMX+ new asssembled powers on but makes 'chuffing' sound on receive on CW?
Thanks for the replies. I open a?ticket w QRP LAbs and Hans responded that he is sending a new unit.?
He agrees something is amiss with this one.
?He indicated he will pick?up the old unit when he is Dayton in May.?
I thanked him fpr the great support.
Charlie k2cmc
-- ?
Charlie C. ?- K2CMC
LICW/SKCC/NAQCC?
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Ludwig, i checked when display board was completed to main board.?
---------------------------------
73 de Marek SP9TKW
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Re: QMX+ new asssembled powers on but makes 'chuffing' sound on receive on CW?
Hi Charlie,
?
"i get a continuous series of dahs all the time. Even with key and cable disconnected."
I wonder if you have a short on the 3.5mm TRS mic/paddle socket.
Check that there are no solder blobs across all of the pins on the TRS socket and the mini board connecting to the main board.
Also, make sure that the underneath of mini socket board is not touching the casing when you slide the board in (assuming that you have it in a metal housing). There isn't a lot of space between the underneath of the mini TRS board and the casing. I had a slimier issue after completing my QMX+.
?
Mel. M0KMD
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Re: QMX+ with 100 amp/hour lithium iron battery
I used 7812 and there was slight noise. I returned to one diod instead and everything is ok now. 09:32, 11 April 2025, "Alan G4ZFQ via groups.io" <alan4alan@...>:
On 10/04/2025 18:28, Petrov Sergey via groups.io wrote:
?It generates slight RF noize. Which is annoying.
Do you mean the 7809 is producing RF noise?
If so, then suspect the decoupling capacitors.
A 7809 should be noise-free.
73 Alan G4ZFQ
--
Sent from Yandex?Mail for mobile
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Re: QMX+ with 100 amp/hour lithium iron battery
On 10/04/2025 18:28, Petrov Sergey via groups.io wrote: It generates slight RF noize. Which is annoying. Do you mean the 7809 is producing RF noise? If so, then suspect the decoupling capacitors. A 7809 should be noise-free. 73 Alan G4ZFQ
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QMX+ new asssembled powers on but makes 'chuffing' sound on receive on CW?
Hello i have received my assembled QMX+ a few days ago and go the power cabled assembled feeding this unit with 11.80v of dc. (12v model)?
I can putty into it and see the hardware tests pass, the data sheet shows all good on all bands.?
It powers up and down fine. I have not xmited w it yet.?
I can viewed the manual that i downloaded and printed out for vx.0027 of my software?
Still not sure of how to operate it.?
When i turned on practice mode or keyed i get a continuous series of dahs all the time. Even with key and cable disconnected. ????
If i put the unit in vfo mode it seems to go away. Volume., are and band changes seem ok.
I got thsi to stop but not sure how???
on any band cw i get a continuous audio chuffing sound like its sampling or some such.?
I can use some help or guidance on this and i am not transmitiing until i get this sorted out.?
Can i or did i change a settting in the config when i puttyed in?
Maybe its my ignorance of how it operates??
Thanks in advance?
Charlie k2cmc
-- ?
Charlie C. ?- K2CMC
LICW/SKCC/NAQCC?
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Just got my QMX+ last week in the US; DHL at least at the time didn't charge any brokerage. It's under $800 and so the de minimus applies.
As others have noted, when I lived in Canada dealing with those import fees from the Fedex, UPS and DHL cartel was much, much worse. The only carrier in Canada that was at all reasonable with fees was Canada Post, but it's a lot slower to ship through standard post.
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Re: Here's hoping for QMX+ v2
On Thu, Apr 10, 2025 at 11:36 AM, George Korper wrote:
I purchased an amazing $140 mini PC and use a USB cable.
Please share the details.
Thanks and 73, Don N2VGU
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I think you will be OK. Nothing has changed for US. Relax.
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Re: Here's hoping for QMX+ v2
I'm using this amazing and cheap PC using a Raspberry Pi4-B with 8GBit RAM and Rasbian OS (a Debian Linux OS) sold at the low price of US$219 and working well. It has a choice of 2 OS to boot and I added to the original Rasbian OS the HamPi OS, the latter being a Hamradio Linux OS with all necessary Ham radio softwares installed.
?
73 - Pierre - FK8IH 
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QMX+ with Elecraft KXPA100 amp..;-)
Ok,,,, just for fun I thought I would try my QMX+ with my KXPA100 amp and *it works great*... puts out about 50 watts with QMX+ driving it.
?
I made my first SSB contact in QRP mode on 20m the other day but since the bands are not that great and I have this amp normally hooked up to my KX3 I thought I would see how hard it was to get working... EASY.. just set the PTT on each band to "grounded" and I have a TRS-to-RCA breakout cable (not sure I have that but...) once I figured out which RCA plug was which, I just plugged it into the KXPA100 and bingo! ?Plus since the KXPA100 has an ATU built in I can use that as my tuner !
?
Pretty cool...just wanted to toss that out there in case anybody else was thinking "QRO".... ?
Of course.. NOT a cost-effective solution...;-)
?
Mark
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Todd W2TEF
Marek SP9TKW
Donald S Brant Jr
Pierre - FK8IH