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Re: QMX: C516 - C525 swapped value #qmx

 

On 27/02/2024 15:45, jh4vaj wrote:
t appears that the values of C516 and C525 are swapped between the schematic and the manual.

"The current assembly manual is correct: C525 is 270pF and C516 is 180pF. "

Be careful, simulations must account for stray capacitances.

73 Alan G4ZFQ
QMX: C516 - C525 swapped value #qmx

 

?
On the QMX rev.2 PCB, it appears that the values of C516 and C525 are swapped between the schematic and the manual.
I have run simulations and the values in the schematic seem to be better.
What do you think?
Re: QMX v3 rev017 Digital Modes Receive Gain Low

 

You can adjust input gain in the terminal configuration menus.
73
--
David Thomas M0OOR
Re: QRPp

 

?? I agree!
--
?

73, Barb
Re: QRPp

 

You are right Hans! I forgot to mention the most important point! I lower voltage to 5V! Getting old!! Sorry for the snafu!

ROFL... and we can celebrate this fine Tuesday with one less mystery to worry about!

73 Hans G0UPL
Re: Faulty Progrock2 - no response to ticket #progrock2

 

I have used numerous ProgRock2's without any problems -- I install them in old receivers and transmitters to replace faulty/drifted crystal-based heterodyne oscillators.? What are you trying to do and what went wrong?? Possibly I can help.

73 - Steve, KW4H
Re: #qmx filter testing and adjustment #qmx

 

Did you made the output transformer in the WSTS style?

73, Ludwig
Re: #qmx wrong inductances for LPF? #qmx

 

Hi Nate


On Mon, Feb 26, 2024 at 07:43 PM, <natereik@...> wrote:
? ? Am I understanding that you were finding T37-17s to measure 25%+ high when you wound them??
And your further work with T37-10s is validating your measurements?
From Material 17 I used the size 30 (T30-17).
Validation by using T37-10 showed two things:
1. My setup brought probably to high values for L.
2. Despite the deviance (see No 1) the AL of the T30-17 (QMX) could be probably a little bit to high but probably not +25% or more.

With 12 turns on a T37-17, I was somewhere around 0.35uH. Taking it all the way down to 8 turns got me 0.22 ?H
These values are not consistent. Reducing from 12 turns to 8 should reduce the inductivity by theory from 0.35 ?H to 0.16 ?H (not the measured 0.22 ?H).
Did you use the same allocation of turns across the toroid?

I'm considering building a whole LPF on a breadboard
Please be aware of the different stray capacitance and the capacity of the connected QDX circuits. And use a rf suitable board!!!

My final result of my whole testing was: Following the manual brings good results or at least a good start point to tweak the filters.

73 Ludwig
Re: QRPp

 

You are right Hans! I forgot to mention the most important point! I lower voltage to 5V! Getting old!! Sorry for the snafu!
--
?

73, Barb
Re: QRPp

 

Hello Barb?

?I have QCX V1 and I adapted for usdx and used it with 1x BS170 without any problems many months. The PA efficiency is 60 to 70% which does not create significant excess heat.

The maximum power dissipation of a BS170 according to the ON Semi datasheet (these are the devices we supply) is 0.83 Watts.?

If a QCX was producing 5W output at 60% efficiency the heat dissipation would be 3.33W. Rather a lot for one BS170 rated 0.83W. I'd be surprised if the BS170 could handle such a thing...?

So I'm not sure what is going on there... something sounds not quite?right to me. I'd expect the output power would be somewhat reduced because the "ON" resistance is 3x what it would be with three BS170 in parallel. However I'd expect the power reduction to be relatively modest; the output power wouldn't be reduced to 1/3 of its three-transistor value...?

So I'm at a loss to explain the survival of your BS170 but all power to it! (err, literally)
?
73 Hans G0UPL
Re: QRPp

 

Hans,

?I have QCX V1 and I adapted for usdx and used it with 1x BS170 without any problems many months. The PA efficiency is 60 to 70% which does not create significant excess heat.

?Actually that QCX is my QRPp rig which I still enjoy. I know that usdx is not the QCX firmware though I think they share the same QCX ghetto class E PA design regardless of firmware as hardware topology.

I like to experiment and this suggestion was through my experiments that I carried out so ?here is the disclaimer listen to Hans and do not try this at home if you are not into experimental ham radio operation!:)
--
?

73, Barb
Re: QMX Diagnostic Power Out Vs Meter

 

Wrongly wound SWR transformer?


On Tue, Feb 27, 2024 at 1:53?PM bcharbour78 via <bcharbour78=[email protected]> wrote:
I've got a homebrew QRP power meter (photo of schematic) and it showed 17.7v (+3w) in my DVM.? That's quite a bit more than <.5w!? I'm gonna go back and reflow the toroids and transformers.? Maybe that'll show a better power out reading in the diagnostics.


--
Bill Harbour
K4VIB

Re: QMX if Vaudeville Still Existed

 

Abbott & Costello did a great variation on it using "Susquehanna Hat Company" as the trigger phrase.
Re: QMX Diagnostic Power Out Vs Meter

[email protected]
 

I've got a homebrew QRP power meter (photo of schematic) and it showed 17.7v (+3w) in my DVM.? That's quite a bit more than <.5w!? I'm gonna go back and reflow the toroids and transformers.? Maybe that'll show a better power out reading in the diagnostics.


--
Bill Harbour
K4VIB
Re: QRPp

 

Hi Barb

> The easiest mod is to remove 2xBS170 and run on one BS170.
> QCX will be in QRPp range now with this mod.

No... all you do then is fry the BS170. The point of multiple BS170's is less about reducing the effective switch "on" resistance due to paralleling multiple devices. It's more to do with the fact that the power dissipation rating of one device is inadequate. Paralleling multiple devices shares the power dissipation. If you use only ONE BS170 in a QCX then the power output will reduce slightly (due to the higher "ON" resistance of only one) but all the power dissipation will end up in that one transistor, and it will suffer untold pain and suffering.?

73 Hans G0UPL



On Tue, Feb 27, 2024 at 2:19?PM <wb2cba@...> wrote:
The easiest mod is to remove 2xBS170 and run on one BS170. QCX will be in QRPp range now with this mod.
--
?

73, Barb
Re: QRPp

 

On 27/02/2024 11:19, wb2cba@... wrote:
The easiest mod is to remove 2xBS170 and run on one BS170. QCX will be in QRPp range now with this mod.
Barb,

I wonder.
I seem to remember that essentially the paralleled devices share the load. That has been mentioned with the U3S.
Would just one be overloaded?
In any case if the power was reduced to 1/3 it still would not be QRPp depending on the definition of QRPp:-)

73 Alan G4ZFQ
Re: QRPp

 

The easiest mod is to remove 2xBS170 and run on one BS170. QCX will be in QRPp range now with this mod.
--
?

73, Barb
Re: QMX Display Brightness

 

Hello Chris
?
Question for Hans, are there any plans to be able to control the LCD display brightness in software?? Superficially it seems easy to drive the LCD_LED line with a PWM output which can be adjusted in software to set the brightness.? The existing Backlight ON/OFF setup could be changed to set a number 0-99 maybe.

Or is there a killer? The timer or PWM registers already in use?

I didn't have any plans for such a thing... the LCD_LED line is not connected to a Timer PWM output. Which makes it harder (not impossible); PWM'ing 10mA of LED would also inflict a heavy noise penalty which is why it would be really hard to do cleanly, unless it was reconnected to a Timer pin so could be done by the microcontroller in hardware (timer peripheral) not in software.?

I'll keep it in mind for future, it isn't trivial though.?

73 Hans G0UPL
Re: QMX Display Brightness

 

Question for Hans, are there any plans to be able to control the LCD display brightness in software?? Superficially it seems easy to drive the LCD_LED line with a PWM output which can be adjusted in software to set the brightness.? The existing Backlight ON/OFF setup could be changed to set a number 0-99 maybe.

Or is there a killer? The timer or PWM registers already in use?

Chris, G5CTH
Re: Rotary encoder problem #qmx #rotaryencoder

 

I have the same problem with a V2 QMX that affects both left and right encoders.? When turning the left encoder the volume level sometimes jumps many steps.? With the right encoder I have the issue described above.

????? Don KC6D
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