Date   
Re: Quadrature modulation: The signal behind digital communications | EDN

Eric KE6US
 

There was a recent question in, I think, QRP-Tech group (now on groups.io) asking what level of math is required to understand W7ZOI's Radio Frequency Design.

This article shows that much of it was covered in high school math (OK, what would be called AP Math today). That doesn't in any way detract from the level of math used by practicing engineers in some cases, but it shows that the level needed to understand and successfully homebrew some very interesting designs is well within the reach of most hams.

Thanks for posting the article.

Eric KE6US

Re: 100+ Amp kits...

Michael N6MST
 

I hope one is in the queue for me! Sister-in-law was asking for ideas on what to get me for Christmas yesterday. I simply sent her the link to the amp page and didn't hear anything back from her :)

Re: Low pass filters

Richard G4TGJ
 

Hi Hans
Thanks for the thorough reply. I tried squeezing the turns but could not get the response to match the expected. I think your point about loose turns is a good one although I did try to make the windings as tight as I could.

So it does sound like their is a toroid issue. Not with the toroids themselves but with the calculations.

I will have to get myself an LCR meter for Christmas.
--
73
Richard
G4TGJ

Quadrature modulation: The signal behind digital communications | EDN

SkipF, NT1G <skip.flem@...>
 

Re: Low pass filters

Hans Summers
 

Hi Richard

There is a lot of variation, but I believe more of it is in winding styles than in the toroid characteristics.

The theoretical values for the number of turns are often quoted. But these are calculated assuming somewhat perfect conditions, including equally distributed winding around the circumference of the toroid. Practically we are often told to leave a from start to end, which some say is for the purposes of minimizing capacitative coupling; the recommended gap is sometimes 30-degrees or 10% (36-degrees) for example. Squeezing turns together increases the inductance; leaving a gap is like squeezing turns together. 

Another thing that increases inductance is looser windings. It's very difficult to wind so tightly that the wire touches the toroid surface all the way round. With fine wire such as the AWG #28 (0.3mm) used in QCX, if you try to pull it too tight, it snaps. With thicker wire, it doesn't bend so easily so it's even harder to get it wound tightly. This also increases the inductance. 

I feel that all this variation in winding style is more to blame for inductance variation than the material tolerances themselves. 

I can't remember having seen a real world measured inductance that is LOWER than the predicted inductance from the calculation. The calculated number of turns always seems to result in too high an inductance value. It makes no difference whether the cores are original micrometals or not. 

I think these differences are all down to the gap between theoretical models and real world situations. 

73 Hans G0UPL 


On Fri, Dec 13, 2019, 13:08 Richard G4TGJ <rpt@...> wrote:
A number of people have had problems with the power output of their QCX and the solution has often been to remove a turn or two from L1-L3. I have been working on my own transceiver and I have been using the W3NQN CWAZ LPF designs from the GQRP Club datasheet. I've been analysing the 20m LPF with my nanoVNA and have had to remove 2 turns from L2 and L6 and 1 turn from L4 to get a satisfactory passband return loss and insertion loss. That's a change in inductance way beyond the 5% tolerance of AL or the 5% capacitance tolerance. Has anybody else done similar tests? Is there a widespread problem with the toroids? Mine came from GQRP Club Sales so I assume they are Micrometals.
--
73
Richard
G4TGJ

Re: Low pass filters

Arv Evans
 

It is difficult for on-line resonnance calculator programs to know how much distributed capacitance and distributed inductance is present in the actual circuit.  This sometimes causes the calculated values to be incorrect.  

Arv. K7HKL
_-_


On Fri, Dec 13, 2019, 4:00 AM Richard G4TGJ <rpt@...> wrote:
Sorry, have you woken up after a bad night?

I've used Tonne Software's Elsie to analyse the W3NQN design and it should work well but my measurements do not match it. So I've hardly instantly come to any conclustions. It was a question for the community to give their considered and informed response.

The problem isn't solved because it means designs may not be repeatable.
--
73
Richard
G4TGJ

Re: New kit: 50W PA for QCX

harleyleenuke
 

Hans,
 Many thanks for the awesome kits.  
Vern

Re: New kit: 50W PA for QCX

Hans Summers
 

Hello Christian 

What a Xmas treat this 50W Amp kit! I could not help ordering two straightaway. And my wife knows ;)
QUESTION: Here in Holland / PA some of use QCX on 80m. Should you find the time: can you please advice on values of the relevant capacitors and inductors so as to make this amp fit_for_use on 80m?

You should use the same values as in the LPF kit http://qrp-labs.com/lpfkit but use higher voltage caps, at least 100V (and make sure they are NP0/C0G) and use T50 size toroids. E.g. T50-2 for 80m.  

P.S.: Given all your effort upgrading QCX-functionality; would it not be an idea to sell (mayor) firmware-updates? Speaking for myself: I would find that completely normal. Guess you need to pay bills just like the rest of us...

I sell the programmed chips (to cover all the costs) but provide the files free to people that want to upgrade it themselves. I've always taken the view that if I provide enhanced functionality, it would increase the appeal of the kit and lead to more sales of the kit (this applies to whichever kit it is - QCX, U3S etc). Maybe that is too naiive, I don't know. 

73 Hans G0UPL

Re: New kit: 50W PA for QCX

Christiaan PA3FUN
 

HI Hans,

What a Xmas treat this 50W Amp kit! I could not help ordering two straightaway. And my wife knows ;)
QUESTION: Here in Holland / PA some of use QCX on 80m. Should you find the time: can you please advice on values of the relevant capacitors and inductors so as to make this amp fit_for_use on 80m?
73's Christiaan PA3FUN

 

P.S.: Given all your effort upgrading QCX-functionality; would it not be an idea to sell (mayor) firmware-updates? Speaking for myself: I would find that completely normal. Guess you need to pay bills just like the rest of us...

Re: 100+ Amp kits...

Stefan
 

Christmas business... :-)
Have fun, Santa!

Re: Low pass filters

Andy Brilleaux <punkbiscuit@...>
 

The problem, as discussed many times on this group is that the transition frequency is a bit too low
for comfort, especially with our little milliwatt rigs.

There's a reason for that, the designer opted actually STATES in his own article that he lowered that cut off freq
so he could use standard value capacitors and also decided to count UP the winding to the nearest whole integer.

Source - W3NQN himself in his own SWM mag article.

It also pays not to use ancient software that relies upon SVC tables in it's calculations.

Gave up that rubbish decades ago.












Low pass filters

SkipF, NT1G <skip.flem@...>
 

Another list member (me!) want to know...do you have any
 inductance meter or bridge? I takes a lot of guessing (and doubting) out of the picture.
Skip Flem, NT1G
Boston-ish

Re: Blown Finals AGAIN!

Alan G4ZFQ
 

And also  one  other was it Q5 or Q6? I am hoping someone can remind me.
The QCX is 40m version  24th October 2017 and it has been giving me sterling service most days.
Richard
If you posted here it will be in the archives.
But really voltage checks are necessary to confirm the fault has not gone further than those components. Sometimes IC3 also goes, a few cases even further back..
Check voltages, remove damaged components if not already done.
Check voltages.

73 Alan G4ZFQ

Blown Finals AGAIN!

R.Putnam
 

It is all my fault. I keyed up without an antenna being connected. ( antenna switch in wrong position!). Last time I replaced MOSFET's Q1 Q2 &Q3.

And also  one  other was it Q5 or Q6? I am hoping someone can remind me. 
The QCX is 40m version  24th October 2017 and it has been giving me sterling service most days.

Richard G0ILN Fist 398.

Re: Error medssage

Giulio Paris
 

Now that the first problem has been solved I have to solve another.
I have resetted the QCX 40 and after the information has been displayed it waits for me to select the band. The problem is that the rig goes into transmission immediately (I checked this with another receiver and saw that the absorbed power increases to around 6 watts) and clearly, as the manual says, the receiving part is disabled and therefore I can't do anything . I suppose that is the switch but it seems that all the connections around the Q5 are well made.
Suggestions on this problem?
Thank you

Re: Low pass filters

Richard G4TGJ
 

Sorry, have you woken up after a bad night?

I've used Tonne Software's Elsie to analyse the W3NQN design and it should work well but my measurements do not match it. So I've hardly instantly come to any conclustions. It was a question for the community to give their considered and informed response.

The problem isn't solved because it means designs may not be repeatable.
--
73
Richard
G4TGJ

Re: Low pass filters

Andy Brilleaux <punkbiscuit@...>
 

sorry for the dratted autocorrect, but I think you get the message :-)

Re: Low pass filters

Andy Brilleaux <punkbiscuit@...>
 

Why do you instantly start blaming toroids ?

Have you not considered that the original W3NQN design was never quite right in the first place ?

It's only now that these days as amateurs so we can easily deal perform the measurements we can see this for ourselves.

As you have seen, you have made a small adjustment and the problem is solved.

Low pass filters

Richard G4TGJ
 

A number of people have had problems with the power output of their QCX and the solution has often been to remove a turn or two from L1-L3. I have been working on my own transceiver and I have been using the W3NQN CWAZ LPF designs from the GQRP Club datasheet. I've been analysing the 20m LPF with my nanoVNA and have had to remove 2 turns from L2 and L6 and 1 turn from L4 to get a satisfactory passband return loss and insertion loss. That's a change in inductance way beyond the 5% tolerance of AL or the 5% capacitance tolerance. Has anybody else done similar tests? Is there a widespread problem with the toroids? Mine came from GQRP Club Sales so I assume they are Micrometals.
--
73
Richard
G4TGJ

Re: 100+ Amp kits...

Mike
 

Congratulations on yet another hit kit.
Seasons greetings to you, yours and your employees.
vy 73 Mike G8NXD

On 13 Dec 2019 at 11:37, Hans Summers wrote:

Hi all

Over 100 people decided to pump up the jam on their QCX kits by ordering
the 50W Amp kit... here at QRP Labs HQ, Burcu has nearly disappeared among
piles of boxes and packing paper, she is doing her best but seems unlikely
to get them all shipped out today! Monday for the rest. See attached!

73 Hans G0UPL
http://qrp-labs.com