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

mike.carden
 



On Sat, Dec 14, 2019 at 5:44 AM jjpurdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
 I told him I wanted to be an Electrical Engineer. He looked at me, then told my parents I wasn't smart enough to go to college and that I should plan on fixing farm equipment.

I can't even begin to relate the impact that had on me.

Ah, great story Jack. :)  Your experience puts me very much in mind of my partner. Her high school career counsellor suggested that she should perhaps work harder on her typing and become a secretary. That advice made her angry enough to pursue a University degree then a PhD. She never went back to challenge the career person, but legend has it that her Mum bumped into him in a supermarket one day and gleefully set the record straight.

I feel I owe that careers counsellor a beer for delivering to me the amazing Dr Mel.

-- 
MC
VK1MC


Re: New kit: 50W PA for QCX

Jerry Gaffke
 

Here's yet another possible option for those that wish to operate the amp at 24 volts.
Though the suggestion from Hans to just turn down the bias might be a better bet,
magnetics is not my strong suit.

I assume the primary issue here is power (and heat), the WA2EBY push-pull IRF510 amp works fine at 28 volts.
We should get the same 50 watts out with a 24v supply as we do with a 20 volt supply
if we change the turns ratio of T3 from 2:3 up to 4:5.

Calculations:
The impedance ratio of the transformer at T3 is proportional to the square of the turns ratio,
so the stock rig has an impedance at the IRF510's of  50ohms*(2*2)/(3*3) = 22.22ohms
Power is   volts*amps  =  volts*(volts/ohms) 
If we increase the RF voltage at the IRF510's by a ratio of 24/20, we should increase the impedance
at the IRF510's by the square of that, up to 22.22*(24*24)/(20*20) = 32.00 ohms.
It so happens that a turns ratio of 4/5 gives us an impedance at the IRF510's of   50ohms*(4*4)/(5*5) = 32.00 ohms

The additional turns on T3 could help performance at lower frequencies such as 80 meters,
but might saturate the core when operating on 10 meters.

Jerry,  KE7ER


On Thu, Dec 12, 2019 at 07:39 AM, Hans Summers wrote:
I use 22V to get 50W on 20m. 19-20V to get 50W on 40m. There isn't that much difference between 22V and 24V. There are also solutions for this - such as turn down the bias. I also found a capacitor at the R5 wiper reduces the power output. Even a few diodes in series to drop the supply voltage would work. It isn't difficult to make it work on 24V supply. There's a lot of design info and measurements in the manual.
 

QCX Not-A-Case

Brent DeWitt
 

I just posted a couple of photos of my somewhat different take on mounting the QCX for desktop use.  More of a presentation stand that anything else.  The only part change was the volume pot, which was exchanged for one with a switch for power.  The "spider" holding the board in the rear and the push button actuators were printed.  Everything else came form Lowe's or Home Depot.  Details and design files for the printed parts are freely available to any list member, just drop me a note.

Thank you again Hans for such a wonderful rig!
--
Brent DeWitt, AB1LF
Milford, MA

Re: New kit: 50W PA for QCX

ajparent1/KB1GMX
 

Smell wreck is impertinent to me and I am very despondent upon it.

Sometimes it can be all proper and correct and very wrong. ;)

Allison
--
Please reply on list so we can share.
Off list email goes to trash, I had to due to scrapers.

Re: New kit: 50W PA for QCX

Paul AI4EE
 

Grammar checkers can be just as bad. In Western North Carolina there is a River named the French Broad. It ultimately sends its water to the Mississippi. There is an Electric Membership Cooperative there by the same name. I had occasion to include them in a report I was preparing for my company. My grammar checker warned me against referring to women in such an insensitive way.


On 12/13/2019 8:06 PM, Brian Summers wrote:
Hans,

Spellcheck? Be very careful. I sent an email to a Japanese friend and wrote 'arigato', which is Japanese for thank you for those who may not know. Not you of course, Hans. Spellcheck flagged it and the suggested replacement was 'rigatoni'. Good thing I checked first!

Brian VE7JKZ

Re: New kit: 50W PA for QCX

Brian Summers
 

Hans,

Spellcheck? Be very careful. I sent an email to a Japanese friend and wrote 'arigato', which is Japanese for thank you for those who may not know. Not you of course, Hans. Spellcheck flagged it and the suggested replacement was 'rigatoni'. Good thing I checked first!

Brian VE7JKZ

Re: Blown Finals AGAIN!

R.Putnam
 

Hi Alan,
Thanks for your response. You have made me dig deeper! I have downloaded The Fault finding pages for transmit signal path and also the transmit block diagram.
73
Richard G0ILN.

Re: New kit: 50W PA for QCX

Art N4EZZ
 

There is a selection of english dictionaries for libreoffice.

Somewhere along the way it turns out that I have installed all of them.

https://extensions.libreoffice.org/extensions/english-dictionaries

Art N4EZZ <n4ezz@...>
GnuPG key ID 0x6712DD0E
=============================
Greed and hate have caused most of the misfortune in the world
throughout history, so we should all examine our motives continually.
Me

On 12/13/19 1:36 PM, Richard G4TGJ wrote:
My LibreOffice (6.3.3.2) has English (UK). This is on Windows 10 - are you on Linux? I don't know if that makes a difference.
--
73
Richard
G4TGJ



Re: New kit: 50W PA for QCX

Richard G4TGJ
 

My LibreOffice (6.3.3.2) has English (UK). This is on Windows 10 - are you on Linux? I don't know if that makes a difference.
--
73
Richard
G4TGJ

Re: New kit: 50W PA for QCX

harleyleenuke
 

Seems like someone added a Hillbilly Spell Checker to the pdf software.  

No worries,  I can understood that whut ya right.

Re: New kit: 50W PA for QCX

Hans Summers
 

Hi Richard

I found the problem with my spellchecker... my document was configured as "English (UK)" but LibreOffice only has an "English (US)" dictionary available. The spell check gave NO complaints... I should have been suspicious about that of course, but missed it in my excitement. So now I have taken the easy solution and configured the language as "English (USA)" then ran the spellcheck and fixed lots of complaints; and ignored when it complained about "colour" hi hi. 

So all fixed now... latest document is uploaded. 

73 Hans G0UPL

On Fri, Dec 13, 2019 at 10:53 PM Hans Summers via Groups.Io <hans.summers=gmail.com@groups.io> wrote:
Thanks Richard

I will correct those errors.

Spellcheck... I did run a spellcheck! Why didn't it find any of it. Arrghhh... will try again...

73 Hans G0UPL 

On Fri, Dec 13, 2019, 22:50 Richard G4TGJ <rpt@...> wrote:
Hi Hans
Another masterpiece and I really enjoyed the circuit explanation especially about the PIN diode switching.But (version 1.00e):
  1. On page 64 section 7.3 you suggest powering the QCX from a 7805. I think you mean 7812 - it says this in section 7.2.
  2. On page 48 "it does occur at 5V for lower voltage settings" should say 5A.
  3. There are very many typos throughout. A spell check would spot these.
--
73
Richard
G4TGJ

Re: New kit: 50W PA for QCX

Hans Summers
 

Thanks Richard

I will correct those errors.

Spellcheck... I did run a spellcheck! Why didn't it find any of it. Arrghhh... will try again...

73 Hans G0UPL 

On Fri, Dec 13, 2019, 22:50 Richard G4TGJ <rpt@...> wrote:
Hi Hans
Another masterpiece and I really enjoyed the circuit explanation especially about the PIN diode switching.But (version 1.00e):
  1. On page 64 section 7.3 you suggest powering the QCX from a 7805. I think you mean 7812 - it says this in section 7.2.
  2. On page 48 "it does occur at 5V for lower voltage settings" should say 5A.
  3. There are very many typos throughout. A spell check would spot these.
--
73
Richard
G4TGJ

Re: New kit: 50W PA for QCX

Richard G4TGJ
 

Hi Hans
Another masterpiece and I really enjoyed the circuit explanation especially about the PIN diode switching.But (version 1.00e):
  1. On page 64 section 7.3 you suggest powering the QCX from a 7805. I think you mean 7812 - it says this in section 7.2.
  2. On page 48 "it does occur at 5V for lower voltage settings" should say 5A.
  3. There are very many typos throughout. A spell check would spot these.
--
73
Richard
G4TGJ

Re: Low pass filters

Richard G4TGJ
 

Hi Luc
Yes, I had assumed I could but hadn't yet looked into it. I like your arrangement and will do something similar. Thanks.
--
73
Richard
G4TGJ

Re: New kit: 50W PA for QCX

Michael St.James
 

Hans,
You are one of a kind and much appreciated. 👍

MikeinMinnesota N0WDM

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

ajparent1/KB1GMX
 

Based on 50 years of doing the engineering thing 11th year math (applied algebra, trig,
and calculus) covered most of the cases in the slide rule era  for all but the most
exotic, computers solved the rest.  

On average a solid understanding of arithmetic helps.  Why?  The most common
problems rely on add subtract, multiply and divide and take a occasional square
root or log.  The latter two were made easier to do with a slide rule and later
pocket calc. The most often use application on my iPhone is the calculator!

For the missing part it is how is that applied and what does it mean.
RFD and EMRFD and SSD are classics that can answer better than 97%
of engineering level questions, the rest you need the antenna design books.
the Radio Amateurs Handbooks over the years were remarkable in the breadth
of subject matter.  As a kid in the 60s they supplied the answers or a good
idea where and what to look for in the library (long before before Altavista
and later google).

Allison
--
Please reply on list so we can share.
Off list email goes to trash, I had to due to scrapers.

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

jjpurdum
 

Takes me back to when I was getting ready to go into the 9th grade. My home town was a small farming community and after the 8th grade, you and your parents went in to meet with the counselor to decide whether you were going to go into a pre-college or vocational track. The counselor asked what I wanted to do (I had my General class license). I told him I wanted to be an Electrical Engineer. He looked at me, then told my parents I wasn't smart enough to go to college and that I should plan on fixing farm equipment.

I can't even begin to relate the impact that had on me. On the plus side, my parents and I ran into him about 10 years later after I got my Ph.D. and he asked if I went to college. I said "Yes" and he asked what I was doing. I said I was teaching at Creighton University. His eyes went as big as pie plates, and he said rather sternly: "You know you'll have to get your Ph.D. to keep teaching." I said: "Yep, already got that." He said: "No shit!" and then apologized to my parents for the foul language. It was a good day.

Jack, W8TEE

On Friday, December 13, 2019, 1:22:49 PM EST, Eric KE6US <eric.csuf@...> wrote:


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

On 12/13/2019 9:17 AM, SkipF, NT1G wrote:

Re: Low pass filters

ajparent1/KB1GMX
 

I'm with Hans on this.

Experience is two T37-2 toroids wound with 20 turns had a  15% variation
in measured inductance at 7mhz using a calibrated P4191A.   One tight 
and closely spaced to maybe 65-70% of the space the other loose and 
covering near 95%.  When stripped and measured the loose one also
had a significant amount more wire, inductance free space or on a
former is dependent on the amount of wire used.  As to pulling hard
enough to break #28 you are likely pulling way to hard.  ;-)

Since iron powder is not spec'ed as exact or even 5% seeing variations 
is nominal case.  Most have a Temp coefficient  +35-50ppm!/degree-C.

What does that mean, if shown a picture of how the sample was wound
one might want to consider that a strong suggestion.  The other is if told
there may be tuning likely because its not a wide band design and can't
be with class-E amp.  Do the tuning.

The tolerances of ferrite (actually its iron powder Txx-xx part not FTxx-xx) ,
caps, and winding style can easily fall out of range.  The first two are verifiable
the third tends to map widely.

Add to that the unknowns like small difference in lead lengths and distributed
capacitance all tend to gang up.  Further L4 and C30 are critical  values
for class E performance and they do interact with the low pass filter.

As to Tonne software and experience while I have always seen errors
when I went back and measured and then plugged in the real values it
was always correct.  One of the items you can plug into models is the
real effect of circuit traces!

What are the real values... inductance of the coils at the operating frequency
(It does change with frequency due to distributed capacitance and mu of the iron
powder inductors).  The actual value of the capacitors, and additional capacitance
of the board or wiring.  If all are 5% (in electronics that is pretty good!) consider
the effect on Fc of a low pass filter, that can push the Fc around by 350khz easily
at 7mhz!

Allison
--
Please reply on list so we can share.
Off list email goes to trash, I had to due to scrapers.

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

Bill Cromwell
 

Hi Eric,

I don't have that book yet but I can get by if I take my shoes off so I can count on my toes as well as my fingers. The 'old' math.

73,

Bill KU8H

On 12/13/19 1:22 PM, Eric KE6US wrote:
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
On 12/13/2019 9:17 AM, SkipF, NT1G wrote:
https://www.edn.com/electronics-blogs/fun-with-fundamentals/4462467/Quadrature-modulation--The-signal-behind-digital-communications
--
bark less - wag more

Re: Low pass filters

ON7DQ Luc
 

Richard,

You do know you can measure Inductance with your nanoVNA very well ?

I made a small "component-adapter", and use it very frequently (see picture).
It's a 4 pin header, two pins to ground, two pins to center of the SMA connector.
I also made a simple 4 pin CAL set,first two pins shorted, center pins open, and a 49,9 Ohm resistor between the last two pins.
(50 Ohm CAL shown in the picture)
The two center "hooks" are bent up slightly to measure SMD components.
Put the nanoVNA in single frequency mode on a low frequency (I use 50 kHz, but using your "working frequency", e.g. 7 MHz,  works too).
73,
Luc - ON7DQ