Andre, quite simply because GPT4 is beyond awesome and could be of great assistance in programming SDR Transceivers like the QMX
but nobody seems to have understood it's capabilities which is a pity.

Paul DJ0CU G4ADF

Useful for probing short timescale propagation. WSPR needs 2 min, FT8 15 sec.? Sporadic-E often fades very quickly :-(? Tropo is more likely to support WSPR.
FT4 as well !?? (might also catch some meteor-scatter, aircraft-scatter)
Multi-mode beacons are more efficient as they can reveal differing propagation conditions.?
Sometimes WSPR is "better" than FT8, sometimes "worse", depending on the timescales involved in the propagation mode.
The more beacon-ing modes, the better :-)? Regards,? Ed? G8BQR

On Fri, Sep 1, 2023 at 11:31 PM, Shirley Dulcey KE1L wrote:

The STM32F446 microcontroller has two 12 bit DACs. A DAC output is used to control the amplitude of the transmitter output; it's not done with PWM. The current firmware only uses that to control the rise and fall times of CW transmissions.

If Q507 is being driven linearly then I hope it has good heat sinking. I would have thought that in order to keep the efficiency benefits if class E you'd want to switch the uc pin driving that transistor from an analog DAC mode to a pwm mode.

On Sat, Sep 2, 2023 at 12:08 AM, Colin Kaminski wrote:

I may have a simplistic view, and I hope to be corrected, but it seems to me that an EER method can only reproduce a single tone at a time

This is sort of the equivalent of saying "but a DAC can only produce one voltage at a time, how can you reproduce an entire waveform that way?"

The magic happens when you do it many thousands of times a second.

What does the waveform of a two tone signal actually look like? The actual waveform, if you squint at it really hard, just looks like a single tone that's being amplitude modulated at the beat frequency between the two tones, and inverts polarity whenever the amplitude modulation has a zero crossing.

An SSB signal, on the air, if you squint at it real hard, is just a single tone that changes frequency and amplitude very rapidly. You can reproduce this by doing the same thing, retuning an oscillator very rapidly and amplitude modulating it.

My totally uninformed guess is that it might come down to being an advantage of the Tayloe mixer used in the QMX over the RF sampling ADC used in the 7300.

On 02/09/2023 07:40, Chris wrote:

The 7300 gave the S/N as -16 to -18.? Ran both at once in Rx and it was consistent, QMX -3 to -5, 7300 -17.? Similar antennas (EFHW and doublet side by side).

Chris,

Maybe the QMX is simply better.
But I would carry out an extended test simultaneously on one antenna with a splitter.
I've done that many times using WSPR. Even then I find results are not conclusive. When I try on different antennas it can get even more confusing.

73 Alan G4ZFQ

A quality set of coil and pot trimming tools...


10-T4857

No connection, just a very satisfied customer..
73 Mike

Yesterday morning, idly running FT8 on my QMX when there was a CQ from New Caledonia, and ATNO for me.
The signal to noise was 0 to -5.? That's from half way round the world!? Tried calling but nothing so got the 7300 going and made the QSO, using about 90W. Cheating, I know but it was an ATNO.
The 7300 gave the S/N as -16 to -18.? Ran both at once in Rx and it was consistent, QMX -3 to -5, 7300 -17.? Similar antennas (EFHW and doublet side by side).

I'm not complaining but wondering why there should be such a difference, the 7300 is working nicely and this difference doesn't seem to be consistent,? I might try analysing the ALL.TXT files for the two systems to see if I can see what's happening.

Chris, G5CTH

开云体育

An even more simplistic view is that the audio signal is a single wiggly line, what you would see on an oscilloscope.? The subtle changes in that generate the multiple tones of speech, even those of a full orchestra.

What seems to be planned is to make changes to the frequency and amplitude of the RF signal to replicate that, with the appropriate modulation.? If you were doing AM all that would be needed would be to change the amplitude. For a 3 kHz bandwidth at least 6000 times a second.? For FM changing the frequency, also 6000 times a second.? SSB needs changing both.?? The challenge may be to synchronise the frequency and amplitude changes so they happen at the same time.

Chris, G5CTH

On 02/09/2023 02:46, W7QJQ wrote:

I did extensive testing of the ProgRock2? reporting the results and starting a thread
*ProgRock2 as a GPSDO and an anomaly***
?in message #101344.? I saw essentially the same thing that did Alan G4ZFQ .

Sid,

Yes, the problem was not addressed, going into long term stability and frequency steps.
I put my Progrock to one side, I did not think I had it good enough for a HF RX or TX reference. I used a different technique and forgot the Progrock.

I only think HF. Roger is looking for a Pluto reference, that goes into the GHz range.

73 Alan G4ZFQ

As I see it, the main limitation, once you have the computing power, is the lack of linear amplification. If you had a linear amp, you would simply generate the IQ data and amplify it.?

I may have a simplistic view, and I hope to be corrected, but it seems to me that an EER method can only reproduce a single tone at a time. The code tracks the loudest frequency and duplicates. The wave shaping circuit changes the volume. ?This can not generate a true two tone signal.?
--
Colin - K6JTH?

Are there any experiences or thoughts regarding the blue vs. yellow displays? Does the blue appear less bright to the eyes? Any opinions regarding readability with old eyes? *(They both look pretty readable in the photos and videos, compared to my (tr)uSDX!

I'm about to place my QMX kit order and I've been contemplating the two display options.

Thanks and 73,
Cal -- AD8Q

A big, big thank you to Hans for a very enjoyable QDX build. Assembly and operations manual were clear and I had no problems with the assembly. QDX worked when first powered. I have made FT8 contacts on all the bands except 80M and 60M since I don't have an antenna for them. CAT control works flawlessly. What a really neat product!
Thanks Hans,
Rob, KF0BFA?

Thanks all for your comments. I decided to solder a 1N4148 diode in parallel to L14.
Additionnally I always tune my EFHW antenna with a transmatch fed by a NanoVNA until it's perfectly tuned.

And to be sure I missed nothing I ordered with my QDX kit a lot of 10 BS170!
73 - Pierre - FK8IH

Dear Karl,
You can add my name to that pool of "lifetime supplies"? I pretty much have them and don't mind sharing.? Pretty soon I will have 200 0805 47jH inductors to add to the Millons of parts I have

Take care and have fun,
73 Dave WA5DJJ?

On 2 Sep 2023 at 2:53, Robert Rabin wrote:

However, I suspect that the messages
could be ambiguous and conflict with those from existing balloon
transmissions. For this reason, I've considered FT8 instead.

are you aware that even the 'custom' data field
in FT8 can contain NO MORE than 13 characters,
including any space characters?

and generally such custom data fields are
entered manually and manually selected from
a drop-down menu if there are more than one
FIXED data fields.

Have you read the WSJT-X User Guide ?

w2jc