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Hi Jim,
Please check to see if message 1or
a portion of isn't hidden on the message 2. Sometimes this can
happen. You may want to erase all of message 2. 50 characters is a lot of space and you can't see all of it at once.
73,
George

John Z and others. Thank you for all the insight and suggestions. I do have a scope but I have limited knowledge. When I get time I will try to do some probing and see if I can find anything.

I have been practicing removal and replacement of some smd chips, but not sure my skills are up to snuff.

It seems I am just one of the unlucky ones as others do have working QMX rigs.

Thanks again for everything!

Alan

Welcome back. A bunch of us do skcc, cw with manual keys. We have a chat page and folk will QRS. I suspect with steady operating your code skill will return. Enjoy however you modulate.

Curt

Just wondering ... Certainly odd behavior.?

Hi

I've redrawn the system schematic to reflect using the HL2 0~17dBm RF output, please see below




And in case the quality is insufficient, there is also a .PDF attached.

Could I please ask that you all take a close look and find errors, suggest improvemnts.

I would really like to thank everyone for their ideas, and suggestions in helping me to get this right, but special mention must go to KB1GMX, thank you Allison.

Than You, Take Care All, 73

Peter - GM8JCF

I have tried powering it from a Talent Cell battery pack & from the same small switchmode supply that I have been using for months, as well as a 5 Amp bench supply - I don't think it is a power issue.
And since the USB cables have been swapped multipule times & USB Ports changed as well, & it still behaves the same on a Dummy Load - I don't think it is RF.
Not sure where to look next..!!

Rob VK5ZIK

Not sure whether anyone else has reported this, but when I play message 2 on my QMX+ it also immediately plays Message 1.

————————-
Jim?
N7RCS
Palm Bay, FL

My QMX+ has the same issue. 1_00_019 works fine. 1_00_020 has unreadable display. The 1_00_020 release is the first one to use all 8 address bits on the LCD. All previous revisions use only 4 of them. Address lines D0, D1, D2 and D3 are now also in use. You should check the continuity end to end from the appropriate LCD leads to the corresponding leads of the MCU. Also look for shorts to ground and shorts between the lines and adjacent circuitry. In my case that all seemed to test good so I am installing a new LCD when it arrives tomorrow.

73 .. .Ron

On Sat, Jul 13, 2024 at 02:36 AM, Donald S Brant Jr wrote:

It is typically well beyond what is needed to measure an antenna's impedance which varies slowly with frequency compared to, say a crystal filter.

Don, usually yes, but the SWR figure from the VNA looks similar to the figure from the QMX, only shifted by some 100 kHz.

73, Ludwig

Here is my I/Q scan on a QMX HB. A far cry from how it's supposed to look. So I guess something is not quite right.

73,

Andreas, K6AKW

When pressing the L/H encoder at the start of the 2 minute .
Instead of starting 0 seconds it starts at 8 seconds.
Using the latest firmware.

Philip G7JUR

Dirk

There was a small group of us here who had a similar problem with the PCM1804 a few weeks ago.

The common symptom was a low resistance to ground from either Vdd or Vcc in the order of a few 10's of ohms.

Once the faulty chip was replaced this resistance was around 2.5k ohms in both cases.

I can't guarantee this is the case for every chip failure, but it's worth a check.

My fault showed as a massive burst of noise for about 3 seconds before decaying quickly to silence....the chip was hot to the touch.

73 Steve G4EDG

On Sat, Jul 13, 2024 at 06:53 AM, ajparent1/kb1gmx wrote:

So the QRPL amp with the HL2 17dBm output is a better match to the task.
If that ends up being too much drive a small low power (50mW) 2-4db
attenuation is far easier to do if needed.

Hi Allison

I rigged up a 50ohm BNC dummy load and connected it to the DSO, (Siglent SDS1102CML+ 100MHz Dual channel oscilloscope), and life is suddenly V good, see table below !!!

Fmeasure=	5398.5	KHz	Zload=	50	ohm
?	?	?	?	?	?
dB Output	Vpp	Vrms(mV)	V^2	P(mW)	P(dBm)
-7.5	1.77	580	0.3364	6.73	8.28
-7.0	1.80	620	0.3844	7.69	8.86
-6.5	1.90	660	0.4356	8.71	9.40
-6.0	2.00	700	0.4900	9.80	9.91
-5.5	2.10	740	0.5476	10.95	10.39
-5.0	2.24	780	0.6084	12.17	10.85
-4.5	2.36	820	0.6724	13.45	11.29
-4.0	2.52	880	0.7744	15.49	11.90
-3.5	2.66	920	0.8464	16.93	12.29
-3.0	2.80	980	0.9604	19.21	12.83
-2.5	2.96	1040	1.0816	21.63	13.35
-2.0	3.16	1160	1.3456	26.91	14.30
-1.5	3.36	1180	1.3924	27.85	14.45
-1.0	3.54	1280	1.6384	32.77	15.15
-0.5	3.76	1320	1.7424	34.85	15.42
0.0	4.00	1400	1.9600	39.20	15.93

So the RF1 17dBm output is indeed fully variable, and a simple fixed 3dB attenuator between it and the QRPLabs 10W PA should bring down the drive level to around 25mW.

The "dB Output" data are the values from the "Drive Control" in the Thetis SDR s/w, ie 0dB is full power out

Thank you ever so much for your suggestions, and prompting me to try the 17dBm output, this certainly makes for a cleaner/simpler design both philosophically and practically.

Thank You once again, 73

Peter - GM8JCF

On Sat, Jul 13, 2024 at 11:36 AM, G8JCF wrote:

The 17dBm output is very attractive, but I'm not sure if it's variable, eg if the "drive control" in the various SDR s/w can control the drive level, or if the drive level is fixed at 17dBm

I've taken a look at the HL2 schematics, RFFrontend.sch and PA.sch - and the drive to the 17dBm connector, "RF1", and the drive into the 5W PA come from the same pins on the FPGA, so it looks like the RF1 RF level should be variable. Looks like I'll just have to hookup the 50ohm dummy load and 'scope the signal at RF1 and hopefully find out that it's fully variable, now that would be a neat solution.

73

Peter - GM8JCF

On Fri, Jul 12, 2024 at 11:02 PM, Steve G4EDG wrote:

I reduced the attenuation and was able to drive the amp to the full 100w with 5w.

Hi Steve

That would mean voiding the warranty, and I'd rather not risk damaging GBP 1,000+ kit if I can do a solid solution with QRPLabs ultra-stable 10W Linear Amp

BTW, do U know where I can get my hands on a BLA-350 plus schematic so that I can add it to the documentation of my BLA-350 plus ?


Thank You

Peter - GM8JCF

On Sat, Jul 13, 2024 at 06:15 AM, John AE5X wrote:

And here is another solution from EU1SW. Costly but offers 14-bit, 6m and 160m and power to run your amp to full output:

I've already got the HL2, the EU1SW is basically an HL2 with a 20W Linear in an enclosure for about USD400 more than what I paid for the HL2 itself. The QRPLabs 10W linear is about USD70 delivered inc taxes etc, so all I need to do is add some relays, an enclosure, 5 connectors, and of course build the QRPLabs kit, which all in all should come in at less than USD150 (assuming that I buy all new parts)

Thanks for the suggestions

Peter - GM8JCF

Still waiting for the replacement PCM1804, but the Chipquik arrived.

What a great stuff, highly recommended. Desoldering within 2 minutes and no issues.

On Sat, Jul 13, 2024 at 05:45 AM, ajparent1/kb1gmx wrote:

So far you have given a bunch of suggestions that does not get him
that 10W and a few that can barely do what he already has. So stop
polluting the topic with wild and inapplicable ideas.

Thank You Allison, I was beginning to feel like Alice in Wonderland !!

The 17dBm output is very attractive, but I'm not sure if it's variable, eg if the "drive control" in the various SDR s/w can control the drive level, or if the drive level is fixed at 17dBm - I've read lots of manuals but so far haven't found anything which states that it is indeed variable, and it always seems to be referred to as the "fixed 17dBm output"

The variable element is required because here in UK for example there is a 100W PEP max license condition for 60m, 32W PEP max license condition for most of 160m, and of course the general principle to not use more power than is required, so it would be much more convenient if I could just adjust the "drive control" in eg Thetis SDR s/w, rather than fiddling about with different attenuators, although the 17dBm level would be just within the safe operating range of an electronically controlled RF attenuator eg


not as convenient as the on-screen "drive" control, but doable.

Once again, thank you

Peter - GM8JCf

To be precise for transmitting WSPR on 20m:
the actual TX frequency must be inside the mentioned block for WSPR:
20m: 14.097000 – 14.097200 MHz

Now if we use the Beacon mode of a QMX machine then we have to choose the frequency exactly inside that band. For example 14.097130 MHz
But if you do the WSPR using for example the WSJT-X program then by choosing the WSPR mode you get set the 14.095600 MHz. To get the actual transmit frequency you have to add an offset set in the WSJT-X program. Normally this offset is set to 1500Hz. So if nobody changes that all WSPR transmissions would be at 14.097100 MHz. This would be very unfortunate. It is a very good practice to change this offset. For the mentioned example of the output frequency 14.097130 MHz the offset would have to be 1530 Hz.

--
73 Bojan S53DZ