On Tue, Oct 17, 2023 at 02:55 PM, Randy Paulson wrote:

The only functional method I can see is to short the PWR_ON signal, but we need a way to make an outside connection.

Reed relay with external coil??
73, Don N2VGU

I 2nd that request! Is it possible to get this to work in an ancient Heathkit that requires crystals? Examples on how this is done??

Thanks!

73

Roy - KI0ER

FWIW ... I'm using Kenwood TS-440 to connect my logging software to my QMX. It connects via Omni Rig, which is where I have TS-440 as the interface choice. Logging software here is Log4OM.

73!

Roy - KI0ER

I'm in datasheet collecting mode.? Can anyone pass along the manufacturer and part number for the temperature-controlled crystal oscillator used in the QMX?

Thanks!

--John R. Strohm WB5YOO

FWIW I have the QMX connected to WSJT-X and it's working great.

I thought the third harmonic issue with Tayloe detectors was their susceptibility to detect signals at the odd harmonics of the VFO, so if tuned at 7mhz, signals at 21mhz would only be about 9db down ie the susceptibility to detect harmonics of the VFO frequency is not at one third of the VFO frequency.? A LPF is needed to knock down any signals at the harmonics and we already have that for the TX side.

The BPF tracking provided by the QSD provides attenuation of 35db only 20khz either side of the VFO frequency in the QCX (per QCX manual) who knows how far down it is several MHz down (when consider 80m VFO that might be impacted by MW frequencies).

Great to see some testing and measuring being done on this issue of what impact the front end BPF circuit really has.

73


Simon
VK3ELH

If you connect the QMX to WSJT-X and accidentally select an out-of-band frequency, the QMX firmware totally locks up and will not respond to communication, knob turns, nor button presses.

The you have to power cycle the QMX to bring it back to life. This means restarting WSJT-X but it will remember the last setting and try to load the same offending frequency. It's a chicken or egg thing.?

To get things back to normal I have to connect WSJT-X to another radio on a different com port, select a proper frequency and then switch back to the QMX (with fingers crossed).?

It appears that the QMX gets confused by an invalid frequency setting and goes into the weeds. Perhaps there needs to be a fail safe on this setting to ignore erroneous settings via CAT.

73, Randy K5HJ

Apologies if this has been covered before, I tried a search and didn't find what I'm looking for.? I finished my second QMX (less said about the first one the better) today and it's working great.? No problem connecting to my PC running Linux mint and TX/RX seem to be fine.? The rig connected to PUTTY as it should and everything looks fine.? But I cannot get it to connect to CQRlog.? In fact when I try to connect it freezes the program and I have to quit the program.? I have not yet tried WSJT-X.

Is there something I'm missing?? I used Kenwood TS-480 and tried several /dev/ttyUSBx configurations.

73, Bill NZ0T

KE0WVA,

Your doing a work around for a winding error.
Your claims for BCI are not even close to my environment.

I have many stations that are part of the eastern MA broadcast nexus most less than 7miles
from my home and a few closer (AM broadcast) , so band pass and high pass is required here.
In some cases weak designs (hobby and commercial) need a high pass filter to function well.
Add to that more than a dozen hams on HF within 3 miles, some using 160 and even 630M.

The series inductor is a low pass structure.? However the resonating capacitor in series creates
a high pass node.? That they are resonant hopefully mid band is critical.? Winding L401 wrong
is an error and should be fixed.? That you are not close enough to broadcast stations to not
have issues is just good fortune.

Study the circuit and do the sheet of paper analysis by eliminating the CMOS switch
(IC402) and simplify it to L401 and C401/2/4 in series.

For those that want to delete L401 a jumper from IC402 pin 7 to Ic402 pin9
eliminates L401 (shorts it out).? ? FYI IC402 is a dual 4 position switch so its
easy to? see it how it all lays out.

FYI: if it was really not needed Hans you have left it out and its a safe
bet it was tested both ways.??

---
Allison
------------------
Post online only,?
direct email will go to a bit bucket.

On Mon, Oct 16, 2023 at 10:02 PM, Oleh I2/UY2ZA wrote:

Perhaps you missed my question about current consumption at the output power you specified. Well, very interesting.?

hi Oleh

I didn't, I will look into that next weekend

I oblitrated 3 QDX Ms. waiting for some BS170s and 74ACT08s

73

muhsin TA1MHS

Most phones nowadays can work with any standard USB audio interface... If you have your desired FT8 signal either stored on your phone, or you have an app that can generate it with the appropriate timing, I'm fairly sure you could simply run a USB cable from your phone to the qmx and have it work.

All,

There has been discussion that the series LC BPF is not required at all.? The validation is to bypass IC402 altogether with a 0.1uF capacitor between RX_IN and the primary of T401.? The BBPF is mainly needed in urban areas where strong transmitters outside the band are likely.

73
Evan
AC9TU

Can you please point me to how to modify the QMX to omit L401?

The naive method I used was to short all of the pads that make up L401's footprint. The easier way that I realized later was to simply short pins 7 and 9 of IC402.

BTW a clean square wave has only odd overtones, so the fist overtone for 1700 kHz would be 5100 kHz

Oh, of course, how silly of me.

Bojan Naglic: I agree that you gain nothing at lower frequencies but you loose about 13 dB at the frequency you want.
Please see the charts in the attachment.

I'm not sure what this graph is trying to show?

Rod Smith: So tuning your NanoVNA around 1.1667 might well produce a significant audio tone (but depending, as you say, on the attenuation afforded by antenna and tuner), as might the fifth undertone around 700KHz

Well, yes, but this would be because the actual signal entering the radio actually contains that harmonic. Even a sharp bandpass or high pass filter that perfectly isolated the band of interest wouldn't filter this out, because it's a signal, not an artifact. A real AM radio station would not be allowed to generate harmonics so strong that they interfere with the amateur radio band, so if we're interested in the effects of nearby AM radio stations we're really only interested in the consequence of a strong signal at the station's fundamental frequency. I'm interested in seeing if there is a realistic scenario where an out-of-band signal generates an artifact in the band of interest, either in the form of a spurious signal or increased noise floor. The primary goal of my experiment was to see if even a very strong signal in the AM radio band, stronger than anyone could realistically ever expect to see hitting the front end of their radio, resulted in any ill effects. I'm fairly satisfied that between the high pass characteristic of C401/402/404, and the selectivity of the tayloe detector, that L401 and the construction challenges it presents is unnecessary for good performance. I welcome anyone to provide evidence to the contrary.

Hi Bojan,

Thanks for the screen shot example of how elsie works. I might have to see if I can get it to work on Wine emulator.

One thing to keep in mind is that, because of the stray shunt capacitors at both sides of the inductor, the insertion loss of the BPF will be greater than predicted by your simulation. Also, for the same reason, the rolloff on the higher frequency side of the center freq will be steeper. That is both in simulation and in real life measurements.

OK - I'm making progress and sort of see what's going on.?

?I power up QMX and go right to FLRIG, it works. However, if I power up QMX and then go to MacLoggerDX, not only does it not work, but it seems to bugger up something with that port and FLRIG will no longer works. I have to power off QMX and back on before FLRIG will work. So, it seems that MLDX not only does not connect, but it is also messing things up and confusing the heck out of this debugging process.

?I'm kicking this back to the MLDX guy as it appears to me to be 100% in his ball park to fix.

?Cliff - thanks for the reply!
--
Jim / K7TXA
Eagle, ID

SKCC 10447C
BUG 301

开云体育

Jim,

Hi Stephan, as Gunnar begins to suggest - the QSD will respond far more strongly to frequencies at one third of the LO injection frequency than those at one half.? So tuning your NanoVNA around 1.1667 might well produce a significant audio tone (but depending, as you say, on the attenuation afforded by antenna and tuner), as might the fifth undertone around 700KHz.

As for series inductors -? of course in isolation they don't result in low frequency roll-off but in series (or, for that matter, in parallel) with a capacitance they can usefully emphasise a wanted frequency vs unwanted lower frequency (as well as higher).

73
Rod
G0VKX
one time G8FJN (but sadly the authorities no longer allow me to hold both callsigns)

Has anyone come up with a way to remotely power up-down the fabulous QMX??
Without drilling any holes in the QRP Labs custom case. It's just too clean to deface if I can avoid it.
The only functional method I can see is to short the PWR_ON signal, but we need a way to make an outside connection.
I've considered leaving out one of the enclosure screws and slipping a small wire through that hole, but then I have dangly dongle thing hanging there.?
Still, that may be the only option short of finding the thinnest 2.5mm stereo jack and mounting it on the display board above the DC jack, and drilling a hole in the end plate.
Once I get a way to connect outside I can use a momentary relay pick from a Tuya or similar device to signal PWR-ON/OFF.?
Any other Ideas or solutions out there?
Thanks!
--
Randy, N4OPI

Has anyone been able to connect their QMX (CW Mode) to either FLRIG, FLDIGI, or MacLoggerDX on a Mac computer? I can connect to WSJT-X and PuTTY but that's it.
--
Jim / K7TXA
Eagle, ID

SKCC 10447C
BUG 301