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Re: QMX firmware todo list?

 

Hi all,
?
I am a new user of the assembled QMX. Experience of using approximately 2 weeks at home with a stationary antenna in CW.
It is very important for me to fix:
?
1) Sidetone volume control;
2) AGC (On / Off).

Both (1. and 2.) because sudden and very loud noises disturb other family members at home late in the evening (or, I think, when traveling in future).
Constantly turning the "VOL" encoder back and forth is very tiring, but there is no other way now.

And, if possible, for convenience I would like:

3) Indicator or meter during QMX RX/TX operation:?
? ?RX - S-metr
? ?TX - SWR-metr (or simple indicator, for example: "OK" for SWR<2 and NOK for SWR>2).
4) "Logarithmic volume control clockwise" (tnx Bojan S53DZ).
?
But QMX is really a cool thing! TNX Hans!
?
Regards and 73! de Alex YL3BU
Re: replaced SMPS cards and the QMX is not detected by win 10 to load the firmware.

 

did you read this description?
--
Gyula HA3HZ
Re: replaced SMPS cards and the QMX is not detected by win 10 to load the firmware.

 

Giuseppe, The qmx pin out drawing is very useful to me.? My qmx will only turn on and? get as far as the splash screen and thats it(it wont turn off).? I carefully checked all 10 pins in the diagram? only one has an incorrect voltage. My ADC_5V shows only 2.5v (dc)should this be 5 volts?
i replaced the SMPS boards.? Is my 2.5v to low? I resoldered the pin checked with multimeter and no change. Any advice to get things moveing would be greatly apprecieated.
Re: QDX FDT86256 Mosfet PA Modification

ve3ega
 

Peter,

I just found this link for a 'parts kit; (or assembled) for the "QDX Mosfet PA Mod"



I have bought from Jason before, always good support - he has been an electronics/radio kit supplier for Years!

73

Terry
Re: LPF Sweep for QDX and QMX #qdx #qmx

 

Hi Evan, Chris, Ryuji

I can quite easily set up a sweep in QMX based on power output measurement. Everything interacts with everything. I don't think you can make too many assumptions about symmetric BPF sweep etc. So it'll be just a "for what it's worth" indicative kind of a sweep. Best we can do...

FYI yesterday I got Power and SWR working nicely on my QMX. I added it to the diagnostics screen in the terminal. And also the LCD during transmit. It shows both power out and SWR in the 3 LCD characters between the mode indicator and battery voltage icon. Power is 0 to 6W full scale deflection whereas SWR shows 1.0 to 4.0 with each "bar" worth 0.2. I also added a configurable SWR protection feature.

73 Hans G0UPL


On Fri, Sep 22, 2023, 8:06 PM Evan Hand <elhandjr@...> wrote:
Hello Hans,

Thank you for the response.

For the current QMX, using the unused 0 BPF selection on IC402 might be possible.? That could be set up with jumpers to bypass the BPF.? That does take up one of the BPF selections.? Is it possible to factor in the BPF response based on the assumption that the lower half of the frequency response is the same as the upper half?? That could be factored into the measurements.? I am unsure if that would be accurate enough for adjustments.

It was just a suggestion and at a much lower priority than anything on your current list.

73
Evan
AC9TU

Re: QDX FDT86256 Mosfet PA Modification

 

Hi Ross,

I played with this a bit more this morning.
To answer your question about the sim of the transformer, at the moment I simply use three coupled inductors with K=1. Nothing fancy.

Some additional comments from my dabbling this AM:

The current-fed mode for this amplifier runs with all?kinds of odd behaviors. Not the least is an EOT spike that hits 160 volts and a hard limit there that looks like breakdown. I haven't yet spotted what in the model sets the breakdown point.

I get much better results running these devices in voltage-fed mode, using a 100nF capacitor at the CT of the output transformer. No spike, all waveforms are cleaner, higher output power. Still SMH about that. Optimizing the transformer ratio remains TBD.

The Vth of the model is currently set at 3.85 volts. With a 5V supply tied to the driver chip models, a drive up level of only 4.6 volts is obtained. This is a bit low for driving this transistor. Turning up the logic supply to 6V produces a much more satisfying result and substantially improves the drain voltage down-level and the output power. This is not practical, of course, but serves to illustrate one issue with the use of these transistors.

More later. There is still much to be explored.

JZ


On Sat, Sep 23, 2023 at 4:12?AM Afghan Kabulldust via <kabulldust=[email protected]> wrote:
Tony and JZ,

What transformer model are you using in the LTSpice sim of the PA? WTST of RWTST? That is a picture of your .asc?
73

Ross
6

On 23 Sep 2023, at 06:59, HA3HZ <gyula@...> wrote:

?
?

I have run it, Tony, but it is still too early to say much. Two of these seem to produce a bit more output power than 4 BS170 in a 20m sim, but the drain currents I see are transitioning sharply and ringing wildly. I will play more with it later.
?
JZ
In connection with another experiment, I noticed F5NPV Didier's experiences. Didier applied ES5DOL's suggestion to a Fetes power stage.
He inserted a 0.1...1Ohm and a 220nF capacitor parallel to it between the FET Source and the ground.
With this solution, you replaced the RC elements between Gate and Drain. The latter are meant to stop the ringing.
Perhaps it would be worth looking at this possibility here as well.
Just a small suggestion.
--
Gyula HA3HZ

Re: 4SQRP T41 update

 

Vimeo won't let me watch the video. It says it's unrated, so I have to login to watch it.
Re: QDX FDT86256 Mosfet PA Modification

 

¿ªÔÆÌåÓý

Tony and JZ,

What transformer model are you using in the LTSpice sim of the PA? WTST of RWTST? That is a picture of your .asc?
73

Ross
6

On 23 Sep 2023, at 06:59, HA3HZ <gyula@...> wrote:

?
?
Like
More
?
John Z
12:09am ?

I have run it, Tony, but it is still too early to say much. Two of these seem to produce a bit more output power than 4 BS170 in a 20m sim, but the drain currents I see are transitioning sharply and ringing wildly. I will play more with it later.
?
JZ
In connection with another experiment, I noticed F5NPV Didier's experiences. Didier applied ES5DOL's suggestion to a Fetes power stage.
He inserted a 0.1...1Ohm and a 220nF capacitor parallel to it between the FET Source and the ground.
With this solution, you replaced the RC elements between Gate and Drain. The latter are meant to stop the ringing.
Perhaps it would be worth looking at this possibility here as well.
Just a small suggestion.
--
Gyula HA3HZ

Re: QDX FDT86256 Mosfet PA Modification

 

Hi
To be tested! (as soon as I got FDT86256s)
In QCX, QDX or QMX (If you have one more to obliterate)
Use 9 Volt setup (Ross's new windings)
Use FDT86256
Pray, then
Apply 12 Volts (top case open, a fan blowing in)
Mamma Mia
73
Muhsin TA1MHS
?
Re: In praise of the humble BS170 MOSFET

 

¿ªÔÆÌåÓý

It sounds like the UL3S is best suited for weak signal digital modes like WSPR and that the QCX- mini would be better suited for a CW beacon and the QCX has some other amazing attributes like CAT control which opens up the possibility of remote control which is beneficial since my 10m beacon is over 100 miles from my home QTH. ?I¡¯ve experimented with the CAT and it works very well. ?I have a QCX mini that I built then accidentally destroyed the CPU out of shear clumsiness but I went ahead and ordered a replacement today. ?I think it put out a solid 3 watts before I destroyed it. ?But I might also experiment with the UL3S to increase power output by adding a driver or an outboard amp. ?

-Jerry, AC5JM?


On Sep 22, 2023, at 2:14 PM, Shirley Dulcey KE1L <mark@...> wrote:

?
That's why other QRP Labs designs like the QCX and QDX have a driver stage. It's pretty simple, using some CMOS gates, but it's enough to drive the BS170 transistors. The U3S is a QRPp transmitter (under 1W) so it doesn't bother with the driver.

On Fri, Sep 22, 2023 at 1:45?PM Alan G4ZFQ <alan4alan@...> wrote:
On 22/09/2023 17:38, John Z wrote:
>? ?I think the total capacitance may
> be too much for the chip to swing at 28 MHz.

I think the reason is that they are not driven hard enough just by the
Si5351. Maybe add a driver?

73 Alan GZFQ
Re: old verses new output transformer for QDX digital transmitter

 

Hi,

I've made the current verses band as attached.? for the 13.8 key down was only for a second to get the current reading.
This time used a analogue watt meter to check output and corresponds to my digital meter.
I will set it up for operation on 20 meters WSPR shortly if anybody wants to see the results on WSPRNET?
Cheers and 73
Ray? VE7AVG
Re: QCX Mini Surface Mount Resistor Disaster

 

P.S.? I'm sure I have both 0805 and 0603 1nF (aka 0.001uF, aka 1000pF) caps in my stock.
Re: QCX Mini Surface Mount Resistor Disaster

 

Hi Chris,

If you are not comfortable going down the SMT road, I will fix the board for you free of charge if you send it down to me in NJ (and pay return shipping).? I am good on QRZ.

73,

Robert, WA2T
Re: QMX Volume encoder

 

Brad, that link did not work to me, it took me to an HDMI cable.? Just go to amazon and put?B07D3D64X7 into Amazon's search bar ti see the encoder.

73!? Mark K9TR
Re: old verses new output transformer for QDX digital transmitter

 

¿ªÔÆÌåÓý

Thanks Barb.

Milt w8nue

On Sep 22, 2023, at 5:09 PM, wb2cba@... wrote:

?

Milt,

All covered in this document for old and new winding:


73

Barb WB2CBA
Re: QDX FDT86256 Mosfet PA Modification

 

I have run it, Tony, but it is still too early to say much. Two of these seem to produce a bit more output power than 4 BS170 in a 20m sim, but the drain currents I see are transitioning sharply and ringing wildly. I will play more with it later.

JZ


On Fri, Sep 22, 2023, 5:57 PM Tony Scaminaci <tonyscam@...> wrote:
JZ & Barb,

Looking at the FDT86256 data sheet, it has about the same gate threshold range as the BS170. The IV ?curves show the drain current pretty much flatlining at 1A for Vgs = 5V which is again pretty close to the BS170. I¡¯m wondering what the performance of this device would be in our LTSpice sim of the QDX PA design. Have you tried this yet John? I¡¯ll give it a whirl if I get some time.

Tony - AC9QY

On Fri, Sep 22, 2023 at 1:01 PM John Z <jdzbrozek@...> wrote:
To all interested in the FDT86256,

OnSemi posts a PSPICE model for it here:


It is a .SUBCKT type model. It runs well in LTSpice. That FDT86256 is
a pretty zippy transistor!

JZ KJ4A

On Fri, Sep 22, 2023 at 10:16?AM Ryuji Suzuki AB1WX <ab1wx@...> wrote:
>
> Hi Ross,
>
> The load impedance given to the final transistor is largely decided based on the load line (voltage swing, bias point and the target output power) and not by the device's intrinsic large signal impedance characteristics. The latter is very difficult to measure and it is also often not used in practical RF amp designs. In other words, most power amps' operating point is set to pull the desired power output and that is at a theoretically mismatched condition.
>
> So, once the supply voltage, bias point and the transformer are decided, the output power range comes with that decision. Fixed ratios achievable by transmission line transformers are often "rigid" design factors that make certain power ranges popular. RWTST does a clever hybrid windings of transmission line and conventional windings to achieve greater design flexibility with simplicity.
>
>





Re: old verses new output transformer for QDX digital transmitter

 

Milt,

All covered in this document for old and new winding:


73

Barb WB2CBA
Re: QDX FDT86256 Mosfet PA Modification

 

JZ & Barb,

Looking at the FDT86256 data sheet, it has about the same gate threshold range as the BS170. The IV ?curves show the drain current pretty much flatlining at 1A for Vgs = 5V which is again pretty close to the BS170. I¡¯m wondering what the performance of this device would be in our LTSpice sim of the QDX PA design. Have you tried this yet John? I¡¯ll give it a whirl if I get some time.

Tony - AC9QY

On Fri, Sep 22, 2023 at 1:01 PM John Z <jdzbrozek@...> wrote:
To all interested in the FDT86256,

OnSemi posts a PSPICE model for it here:


It is a .SUBCKT type model. It runs well in LTSpice. That FDT86256 is
a pretty zippy transistor!

JZ KJ4A

On Fri, Sep 22, 2023 at 10:16?AM Ryuji Suzuki AB1WX <ab1wx@...> wrote:
>
> Hi Ross,
>
> The load impedance given to the final transistor is largely decided based on the load line (voltage swing, bias point and the target output power) and not by the device's intrinsic large signal impedance characteristics. The latter is very difficult to measure and it is also often not used in practical RF amp designs. In other words, most power amps' operating point is set to pull the desired power output and that is at a theoretically mismatched condition.
>
> So, once the supply voltage, bias point and the transformer are decided, the output power range comes with that decision. Fixed ratios achievable by transmission line transformers are often "rigid" design factors that make certain power ranges popular. RWTST does a clever hybrid windings of transmission line and conventional windings to achieve greater design flexibility with simplicity.
>
>





Re: 50 ohm dummy load mod #dummyload #mods

 

Hi,
considering the price, I suppose you are better off if you buy another QRP D.L. You then have a 100 and 25 Ohm D.L. without cutting anything.

73 Bojan S53FZ
Re: QMX BPF¡¯s pass bands too low.

 

¿ªÔÆÌåÓý

Julian,

Your sweeps look like you used the original build instructions. You need to get the latest, the i version.

You'll need to rewind L401 and see how things look then. In the original manual capacitors C522 and C525 are swapped though in some cases it doesn't make a big difference. They are shown correctly in the lastest build manual.

73,
Cliff, AE5ZA



On Sep 21, 2023, at 16:41, home@... wrote:

While my QMX works the power on all bands except 80m is lower than expected. The frequency sweep is showing all filters except 80m have a low pass bands. I have spaced out the toroidal windings as much as possible, should I remove a turn on L512,508,513,510? Any advice would be appreciated.?<IMG_20230921_211220_203.jpeg><IMG_20230921_211213_010.jpeg><IMG_20230921_211202_613.jpeg><IMG_20230921_211153_657.jpeg><IMG_20230921_211144_352.jpeg>

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