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

4x20 lcd display is the one you want. C103d is the firmware you want. Older firmware have glitches.?
--
73, Dan? NM3A
There are moments when everything turns out right .... Don't let them alarm you; they pass.?

-Jules Renard

Or CTRL-Q
--
73 Bojan S53DZ

Hi,
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.
--
73 Bojan S53DZ

Yippee - that works!! Thanks Ron.

--
Jim / K7TXA
Eagle, ID

SKCC 10447C
BUG 301

I meant to say FEDX not DHL

There software for Linus/winders that using the timing of incoming signals to sync
in time.? The protocol has specific timing and would easy to sync on.?

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

I'm using PuTTY on my Intel Mac mini (macOS Sonoma 14.0) and have a question on using the QMX terminal application. I can get PuTTY to connect to my QMX and the QMX application starts up. I then go to one of the options and drill down to to a task, like hardware testing. However, I'm finding no way to work back up the ladder of menu selections. Once I get at a low level selection, my only way to do something else in the application is to quit PuTTY and start over. Is this normal, or is there some hidden way to step back through the menu selections?

--
Jim / K7TXA
Eagle, ID

SKCC 10447C
BUG 301

开云体育

Whoppie!!!! Nicely done!

Thx!? It will be fun to have that much screen real estate.
--
Jim, W7EZN? ? 73!

An option for audio time sync for WSPR would also be nice. The bulk of the code would be shared with what you proposed above.