BIG Amplifiers with SMALL Microcontrollers and LOTS of Tribal Knowledge

Hi Bill,

I wanted to forward to you a slightly edited email I sent to one of our podcast listener’s as I think this is a really good example of some “Tribal Knowledge”.

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Hi OM,

Ham radio publications are much like the Internet –all that is published must be scrutinized. One such publication had a beautiful QRP to QRO amp using a 3CX800A7. A few watts in and 800 Watts out. My daughter was in FM radio broadcasting and I told her to introduce herself to the station engineer and to look out for any pulls – then the floodgates opened –about a week later I had a 3CX800A7.

So I started to work on the amp. The circuits just didn’t make sense and parts were missing that would make it work correctly. I contacted the author and here is what he shared. He built the amp but never did get to proof the final article. In fact he sent me his notes and sketches which were correct. Thus I could have never built that amp using just the article. I built it for one band, 20 Meters. It has a tuned input and a Pi-L output so is quite excellent on harmonic reduction.

Oh BTW this amp caused me to learn about PIC Microcontrollers. You cannot hit the 3CX800A7 with HV voltage until the cathode is warmed up (must be a female tube). That time delay is 3 minutes. I could not find a suitable time delay relay with a 3 minute delay that didn’t cost an arm and a leg. So that is when I thought about using the PIC16F84 as a time delay relay. Later I ported that over to a 12F675. The cost was less than $10. In the 3CX1500A7 amp ( another free tube)  I have two microcontrollers in there. One is used for a three second step start on the filaments (don’t want to shock the filaments with inrush current) and the second for the 3 minute delay before starting the HV step start sequence.

You can see the “Big AMP” on my website at http://www.jessystems.com.

There was only one problem – I was worried about the cooling of the tube so I made sure there was plenty of air which I dump into a very small sub-chassis and the exhaust is out through the tube. Well “Dah” large volume in and small port for exhaust and you have a jet engine sitting on the desk top. Man it was loud – I would wear headphones when it was working.  When I built the 3CX1500A7 amp I used a larger plenum so not as loud.

There are several key points I want to make about tribal knowledge:

1. Turn off the soldering iron and spend a good deal of time “noodling” over the circuit so that it is clear what each function will do and that all the wires connect to something.
2. Contact the author and ask lots of questions and you might be surprised to find out the published design is not what was designed!
3. Look for uncommon solutions to build problems. Many times parts used in the articles are so unique that only one exists in the whole world and it is installed in the authors unit.
4. The amp was built in 2000 and the use of the PIC16F84 as a time delay for an amp was a bit leading edge but don’t be afraid to employ some advanced technology into your projects. [Today an Arduino built into the amp could do time delay, temperature control of blowers, SWR sensing, grid trip protection and even warm your coffee.]
5. In the Big AMP I figured out how to keep the blower going for about 1 minute after the amp is turned off to “cool down” the tube. The point here is to think about not just the amp itself but refinements to make that $600 tube last for a very long time thus filament current inrush protection and tube cool down.
6. Don’t forget SAFETY – there is 2000 Volts @ 1 amp running around chassis–it is an electric chair sitting on your desk top. I included a microswitch that when the top cover is off it de-energizes the HV circuits. See if you can spot it in the photos.

73’s

Pete N6QW

PS The amp really does exist –see below.

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Pete's Boards Come Alive as a Direct Conversion Receiver (video)

I love it when a new rig is spread out on the workbench like this, pulling in its first signals.  Like First Light on on a new telescope.   These are the same boards you have been seeing in Pete's previous videos:   The Si board, the mixer, and the AF amp.   Now they are linked together in the form of a Direct Conversion receiver.  

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Pete's "Let's Build Something" Audio Amplifier (video)

Who needs LM386 ICs?  Pete goes discrete!   Love the MePads.   And I knew Pete was going to test it with his finger!  He's just taking stray hum from the power lines and coupling it to the input through that Exacto knife.   

Seems to me like these boards is getting close to actually receiving signals.     

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Pete's Mixer (Pictures)

Hi Guys,

 

Just finished building the PD/BM that will be used in the final circuit of the LBS Part I. I will also upload a video of the build.

 

The W1REX MeSquares really work very well and greatly facilitate the build. So the newbie builder -- will have one leg up by using the squares method.

 

73’s

Pete N6QW

Pete's video on this circuit appears below -- just scroll down a few. 

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Bandpass Filter Construction by Pete Juliano (video) TFMS!!!

MePads!   Arduinos!   Breadboards!  SuperGlue!   Graph paper!  Noodling!   Room for Relays!  
TFMS (TUNE FOR MAXIMUM SMOKE!) 

Another great video from N6QW.  Thunder power! 

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Pete Builds a Doubly Balanced Modulator (Video -- Part 3)

Another beautiful piece of cinema from Giovanni Manzoni's Newbury Park Studios.  Bravo Giovanni! 

Pete is obviously a doubly balanced kind of guy.   I liked his use of the W1REX MePads and the breadboard.  Also, the balance pot and the un-balance switch are very handy innovations. 
Most of all I like the way Pete's video takes you from schematic to actual circuit.  

Thanks Pete! 

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SolderSmoke Podcast #167: Arduinos, Amplifiers, Books, and Tribal Knowledge

SolderSmoke Podcast #167 is available: 

http://soldersmoke.com/soldersmoke167.mp3

3 November 2014
Who the heck is Giovanni Manzoni? 
Pete's Bench Report: 
     "Let's Build Something"  Project 
      Arduinos and Si5351s
Bill's Bench Report:  140 watt Amplifier Completed! 
      Low Pass Filter Design with the ELSIE Program
      Samlex Power Supply
     How I almost blew it up! 
     The new amp and the lids in the FT4TA pileup
Tribal Knowledge!
"Nature abhors a vacuum (tube)!"  "The Innovators" by Walter Isaacson. 
Carter, WA9DNF, REALLY knows which end of the soldering iron to grab! 
Meeting with Thomas, KK6AHT.  The two electronic cultures. 
Interviews by Chris, KD4PBJ, at Two Days in Huntsville: 
     Glen Popiel, KW5GP, Author of "Arduino for Ham Radio" 
     John Henry of TenTec
     Steve, WG0AT  

                                               Giovanni Manzoni
Giovanni Manzoni b. circa 1950 Civatavecchia, Lazio, Italy is a noted videographer specializing in the avante garde use of YouTube in ham radio homebrew settings.   Long noted for his insistence on the use of completely home-made video equipment, Manzoni went so far as to demand that his cameras and recorders only use discrete components -- he claimed that integrated circuits "freaked him out."  Manzoni's collaborators have long been puzzled by his claim that all his videos are filmed "on location."  What he means by this remains unclear, however, in a 1997 interview in QST-Italia, he was quoted as saying "No matter where you go, there you are!" 


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OH NO! SolderSmoke Goes QRO! Bill's Amplifier Project (video)

I got the Communications Concepts Inc. EB-63A amplifier working today.  Yea!
Kind of ironic that the highest power amp I have ever built gave me the LEAST trouble.  This just goes to show that circuit layout is very important.  This amp is a proven design, with a proven layout and board.  That's why it didn't turn into a 140 watt solid state oscillator!

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"Science Friday" Interviews Author of "The Innovators" (listen)

Michael Rainey alerted me to Ira Flatow's Science Friday interview with author Walter Isaacson.  I'm reading Isaacson's new book "The Innovators"  (appropriately, on my Iphone 5). The book is very good, with surprisingly frequent references to ham radio.  Flatow's interview with Isaacson is also quite good, and will give you a better idea of what the book is about.  Here it is.  It is worth a listen:
http://www.sciencefriday.com/segment/10/24/2014/meet-the-innovators-who-made-the-digital-revolution.html

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Mailbag: Coils Wound Backwards, Last QSO 1981, Visions of Transistors Keeping Him Awake. Paul has THE KNACK

http://www.pan-tex.net/usr/r/receivers/ra01000a.htm

Hi Bill

I'm just getting back into ham radio after 33 years (last QSO: 1981),
want to do it all through homebrew, seem to have the same mindset as
guys like you and Frank K0IYE, bought your book [love it and Frank's],
and just "discovered" the Soldersmoke podcasts.  I've been listening to
them with one ear as I bike to and from work (about 40 minutes each way, so it's almost perfect).  I'm employed as a digital geek, but yearn for the days of DeMaw's prime (worked him once when he was W1CER), when the 40673 ruled.  I'm very glad that, 40 years later, people like Farhan can weave discrete analog wonders, even if they later choose to use digital *control* (NOT DSP! No!).

I had to start somewhere with your podcasts archive, so I started with
2014 and really enjoyed your struggles with the Herring-Aid 5. My 1st
receiver  was the "DC 80-10" by DeMaw from somewhere around 1970 in QST or the Handbook -- used a CA3028 as the product detector -- and I had similar struggles.  While listening to it, I immediately thought "you wound the feedback coil backwards, you idiot!"

I got my license back in March 2014 and want very badly to get back on
the air with a homebrewed, or at least minimally-kitted, station.  I've
built the receiver:  David White's (WN5Y) Beginner's and Experimenters
receiver[1] heavily modified, have a long wire antenna up, a decent RF
ground, and all the parts I need for QRP z-match tuner, swr meter, T/R
switch, sidetone, and IRF510-based transmitter.  Target:  40m CW by the middle of December, 30m in the couple of months after that with a
fully-Manhattan-style Barebones Superhet and another IRF510
transmitter.  Then one of these BitX things.  It's been a couple of
decades since I felt that there weren't enough hours in the day.  Some
nights I can't sleep, what with all these transistors and simple analog
ICs whirling around...

Anyway, keep it up, I'll be listening.

-- Paul Lender, AD0HQ

[1] I built an Arduino/AD9850 DDS -- a la AD7C -- and used it to tune a
4-crystal filter (10-cent crystals from Tayda!) for the receiver with
the same Rigol scope that you use.  I tried, really tried, to do it with
an analog RF signal generator.  Change is good.  Change is good.

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Dear Santa: I want a Knack Watch. The one with real tubes...

This is what all the cool homebrewers will be wearing next year.   Just be careful at airport security -- they might not understand! 

Check it out:  http://www.johngineer.com/blog/?p=1595

We received some comments from some noted Thermatron authorities: 

Hi Guys,

This will cause all of the bells, whistles and sirens to go off all it once.

Now all that is needed is a logo on the watch that says

EBOLA ( Electronic Bi-state Operational Long Arithmetic) and this will cause you to go to jail without passing Go or collecting $200.

Pete

---------------------

Wow, I love this thing!…even though it uses little black plastic things to work.  Have no idea what they are. (johngineer has knack squared)

Reminds me of a project I am trying with fellow ham.  We picked up an old HP nixie tube freq counter at junk yard.  We were going to strip out the nixie tubes to make a clock, but decided we could make it as clock as is.  Want to program an Arduino thing into generating a frequency that is the time and feeding it into the counter.

For example 3:45:25 would be 34,525 Hz.  

But my Italian is terrible so haven’t been able to get the Arduino to work.  Just learning it.  Project a bit over my head. picked up one of those online language courses on Italian. Hard, but not as hard as Turkish!

Grayson

TA2ZGE - Ankara, Turkey

KJ7UM

Follow the Hollow-State Design Blog

hollowstatedesign.tumblr.com

-----------------------

 I'm wondering if I  could do it Manhattan style, with discrete components... 

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Spark Forever! Pete's First Transmitter

The SolderSmoke legal team (we too use Dewey, Cheetham & Howe!) has advised us to be very careful about divulging the details on this rig.  They are not sure about the statute of limitations.   Beyond what he said on the podcast, all Pete will say is that TOOBs were involved: 1S4, 3S4, 3Q4, 3Q5, 3V4s.  He says power out was ALWAYS less than 100 mw ERP.  That's  his story and he's stinking to it. 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Smart-Phone Cosmic Ray Detector

http://hackaday.com/2014/10/17/detect-cosmic-rays-with-your-smartphone-using-crayfis/
I find this cosmic ray project very appealing.



Also, Adam Fabio over on Hackaday recently posted a Hack-let on ham radio:
http://hackaday.com/2014/10/17/hacklet-19-ham-radio/ 


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"Two guys and a Minima walk into a bar..."

Thomas, KK6AHT, was in Washington this week.  He and I got together for a beer and a look at his Minima. 

I'd seen pictures of it, but it was much more impressive in person.  Thomas did a great job on this rig.  It is a really nice mixture of digital and analog.  I liked the fact that he built the analog portion Manhattan style using MePads.  He and I agreed that while it would make sense to produce a PC board for the Arduino/Si570/LCD portion of the rig, builders should be encouraged to do the rest Manhattan style. 

Showing true homebrew dedication,  Thomas was unhappy with the level of audio output when we turned it on.  He started to trouble-shoot right there in the Ruby Tuesday bar! 

It turns out that we were in a very Knack-ish location.  We were on the site where they created ARPANET. 

Thomas very kindly left me with a nice package of Minima digi-parts including the Arduino chip loaded with the software and an SI570.    So now I have no excuse.  

Thanks Thomas! 

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Arduino Hell!

Hi Bill,

 

I am a long time listener of SolderSmoke and a big fan! Since your last podcast was on the use of Arduino’s for ham radio, my Arduino Hellschrieber project may be of interest to you and your listeners. I am using the $15 dollar RadioShack color display they are closing out and a simple circuit with our favorite transistor!

 

I have a video in my second blogpost and all the details with code below.

 

http://wa6pzb.blogspot.com/2014/10/arduino-hellschrieber.html

 

http://wa6pzb.blogspot.com/2014/10/arduino-hellschrieber-ii.html

 

Keep up the great work, I have your book both in print and Kindle!

 

73, Dan WA6PZB

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Has AA1TJ Joined the FMLA?

I have learned that esteemed homebrewer Michael Rainey, AA1TJ, recently whipped up a 56 MHz, quarter-wave, helical coaxial resonator (BTW: the spoon is also homebrew).  Hmm, 56 Mhz.  Or perhaps we should say MegaCYCLES?  Michael claims this device is for a low phase- noise VFO, but I find the frequency selection highly suspicious.   The last time I heard of that frequency it had to do with an underground group set up by the late (or not so late) Frank Jones.  
Here is all the info on Frank's Five Meter Liberation Army.  

http://www.sunflower.com/~brainbol/frank/

A man of the '30s awakens one night in the '90s (episode 13) with a new mission: recapture 56-60 mc. He forms a Five Meter Liberation Army from his mobile home in a Barrio trailer park run by Tom Joad of Steinback's Grapes of Wrath (episode 9), and soon draws a decidedly uncolorful bodyguard (episode 7). A six foot tall half Mexican stockbroker named for Ayn Rand makes him rich and a demonic white ferret and a half-siamese cat become his familiars. (episodes 10 and 9). The leader of all this, called only "Frank," settles down in the narrator's basement to be joined by Maj. Armstrong (episode 8), Hiram Maxim (episode 23) and one-time pals Carl and Jerry from the 1950s Popular Electronics (episode 25). His huge 1940s sedan, with contemporary plates, is immune from police (episode 13 et seq) and his breadboarded electronic creations recall those distant days when a ham built his own rig and could "fix a radio." Of course all this is crazy. No one builds anything anymore and the other things Frank stands for, like self- reliance, tolerance and a generally Boy Scout viewpoint are simply out of step. Frank knows that too (episode 20), but he does not care. If you're standing in the middle of the road and see a big brown Frazer coming at you, you better jump - one way or the other.

VIVA EL FMLA!  VIVA!


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Tribal Knowledge Video: Putting Screw Threads in Aluminium

http://youtu.be/LuqliWT1k5A

Thank you Giovanni Manzoni, whoever you are! 

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Author Walter Isaacson was a Radio Amateur

This is the guy who wrote the biographies of Einstein, Steve Jobs, and Ben Franklin that I've been talking about on the podcast. President of the Aspen Institutes, former Chairman of CNN and editor of Time Magazine.  And, as I learned today, a former ham radio operator.   In his new book, "The Innovators," he writes:  

"My father and uncles were electrical engineers,  and like many of the characters in this book, I grew up with a basement workshop that had circuit boards to be soldered, radios to be opened, tubes to be tested, and boxes of transistors and resistors to be sorted and deployed.  As an electronics geek who loved Heathkits and ham radios (WA5JTP) I can remember when vacuum tubes gave way to transistors."

When I told Billy about this, he said, "No wonder you like his books so much!"  Indeed.  Walter has THE KNACK.   I'm enjoying his book, "The Innovators."   

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A Different Kind of Workshop

Sometimes it is good to take a break from the electronics and look at how people are making other things.  I've been working on the heat sink for a 140 watt solid state amplifier, so this fellow's comments about working with metal kind of resonated with me.   


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SW Echo Theory Confirmed By a BBC Engineer

BBC Relay Station Singapore

Hi Bill,

I heard your description of the echo on your podcast and before listening I knew the cause - but I think you know that now!

Yes, it's from two separate transmitters, and quite common, though not usually noticed.

It has nothing to do with path length differences - the longest round-the-world echo via the ionosphere is only about 0.15 seconds - so anything more has a different cause.

It's from the audio feed to the transmitter. Your regen receiver picked up two transmitters on different frequencies. It was very noticeable before transmitters used digital land-line feeds, just analogue and satellite.

On a BBC SW frequency (forget the which one now) one tx was in UK and the other in Singapore, on the same frequency with the same programme to completely different service areas. When propagation was right and listening in Europe, the UK signal fed by analogue audio from Bush House came first and the Singapore tx came with two geostationary satellite delays later, plus the tiny bit of UK-Singapore ionospheric path difference.

Now it's worse because there are all sorts of digital delays via land-line and satellite, although using the same frequency for the same service in not common.

In the UK Absolute Radio on AM medium-wave has multiple transmitters (mostly 1215 kHz and 1197 kHz) on the same frequency which are audible at night. If you listen carefully you can often hear multiple (up to FOUR!) echoes from different transmitters all being fed by different internet feeds/satellite links with varying delays. 

As an ex-BBC engineer, I can tell you that in the old days not only were these AM medium-wave group stations all synched to within 0.05Hz, but the phase of the modulation was adjusted so all tramsitters were modulating in phase! Now the commercial boys have taken over most of these syched groups, not only are the frequencies all over the place, but the modulation isn't even time delayed to match, let alone synchronized! Some even put diferent commercials in the breaks so if you're geographically between stations you get a complete, unlistenable-to mess. Apparently these days that's ok.

Why did we bother...?

Anyway, I hope this adds to and confirms your findings.

73,

Ian Liston-Smith, G4JQT

(A grumpy old retired BBC Engineer)

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Swedish Mighty Mite

A thing of beauty!  Check out the key! 

What a great diagram.  Schematic included! 

http://www.sm7ucz.se/MMM/MMM.htm

Remnants of mine

Steve "Snort Rosin" Smith's 

More on all this: 

http://soldersmoke.blogspot.com/search?q=michigan+mighty+Mite

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Thomas KK6AHT's Pacificon Minima Presentation: Noodling! And Maxima Inspiration!

Wow, the Minima presentation by Thomas at Pacificon was really great.   I think he had exactly the right tone and tech level for the digitally-savvy California audience.  His very open description of the ups and downs of his Minima build will surely lure in some new builders, and will at the same time prepare them for the travails ahead!  Great stuff.  I like the mention of Pete's "noodling."  Thomas obviously gets it.  And he obviously has THE KNACK.  Thanks Thomas!  

Thomas has posted his slides and (MOST IMPORTANT) the audio of his presentation.  Just click on the BIG ORANGE play arrow below the slides.  You folks will love this: 

http://www.sarfata.org/2014/10/Minima-Presentation-at-Pacificon/

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Drake-uino! Arduino DDS puts Drake 2B on 12 meter band!

After using the Arduino DDS as a crystal substitute with my 1982 Barebones Superhet recevier (scroll down), I moved back two more decades and used the DDS as a crystal substitute to put my (early '60s) Drake 2B on the 12 meter band.    This was a hack in which I actually used a hack saw -- I used it to cut open the container holding a crystal so that I could make a socket that would carry the signal from the Arduino DDS into the Drake 2B. 

This video is a bit repetitive, but it stated out at two different videos.  I just put them together.  The last part shows the actual crystal socket hack. 

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Arduino DDS meets Barebones Superhet (Video)

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Pete's 17 Meter VXO Transceiver (Video)

Pete:  

I like it!  You and I may be the only people in the world with that kind of VXO range control switch on the front panel!

 

I checked my VXO.   I run it at around 23 MHz.  I use two single crystals, also switched by a relay. 

The 23.144 rock tunes from 23.127 to 23.151    24 kHz

The 23.166 rock goes from  23.144 to 23.168    24 kHz

 So I could have had 48 kHz were it not for the overlap.  As it is, I get 41 kHz.  Not bad.

 

The reason I went with this LO freq was that I had these crystals from the Dale Parfitt/Doug DeMaw Barebones Barbados Receiver.  DeMaw had used color burst rocks for a 3.579 MHz IF, but Dale shifted up to 5 MHz. I could occasionally hear WWV!  (But with the 3.579 I heard W1AW in the IF!)

 

73

 

Bill  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Homebrew Double Balanced Mixers by Pete Juiano (Part II) Video

Another great video from Pete.  I like the unbalancing mod -- I hate having to whistle into the mic!

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Hacker with The Knack Does Well, Working for JPL

Wow.  This guy has a really inspirational Knack story.  He welded (with coat hangers!) a sidecar onto his bike when he was a kid.  He majored in Physics and Theater.  He did all kinds of hardware and software hacks. He plays a Theravin in a band.   He now flies spacecraft for the Jet Propulsion Laboratory. 

And Congratulations to Peter Parker, VK3YE, for having one of his ingenious hacks picked up by Hackaday:
http://hackaday.com/2014/10/06/dusty-junk-bin-downconverter-receives-fm-on-an-am-radio/

Thanks Hackaday! And Happy Tenth Birthday to You!  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Edison is Off The Grid (and has been for 24 years!)

I talked to him last night on 17 meters.  He's a nice fellow.  When your first name is Edison, that's an indication that you might have THE KNACK.   

From his QRZ page: 

Ready for this?
My wife and I have lived off-the-grid for more than 24 years. Solar and wind are our main power sources on our mountain, although, we did finally add a generator to our available power sources, for those long days of "NO SUN" in Winter.  Check out the view from my home at this site:  http://mycampage.com/rosevalleycam  and also look at the other links on the page.  You might find something you like....
I've been a ham since 1967.  Started as a Novice near Sacramento, California, where I was born. But WN6FIC soon became WA6FIC, which I remained until the late 90's, when I became N7GCW.
I am a musician. Along with my wife, and Blaine Lindgren, our fiddle player, we comprise the band called "Half-way There". Click on my campage link to see more about me, and you will find all of my other links there too.  I am also a photographer. I shoot it all, but REALLY enjoy taking pictures of scenery, and live bands at Concerts we go to. I am also very fond of Sunrises, and Sunsets, and they ARE beautiful here.....

Also, check out his TREK page: 
http://n7gcwtrek.weebly.com/index.html

And I liked his description of his county in Washington state: 
"...I absolutely LOVE my world, here in our little valley.  Our friends are like family here.  People smile and wave...and mean it!  We heat exclusively with wood we cut from dead trees on our land, use propane for cooking and refrigeration, and we use solar and wind for most of our power needs, only supplemented by a generator in those long days of no-sun in Winter.  It's like living in a time warp, here in our neck-of-the-woods....  Do you know that there isn't a traffic signal in the entire county?" 
See: http://edisonshomesite.weebly.com/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Pete's Homebrew Double Balanced Mixer Video (Part 1)

Another great video from the famed Italian Director Giovanni Manzoni!  Bravo Giovanni! 

Pete's discussion of double balanced mixers and the associated toroids has made me feel uneasy about my efforts in this area.  I wonder if my diodes were completely matched.  And I KNOW that my toroids are not as well done as Pete's.  

I recently put an SBL-1 into my old, long-evolving 20 meter ceramic resonator DSB rig. Careful with those nice little boxes! A bit too much juice and you can fry the little internal toroids (as I have done!). 

A while back I found in an RSGB Handbook a nice diagram showing how the diode ring mixer does its thing: 


 Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SolderSmoke Podcast 166: Getting Started in Homebrew Radio

SolderSmoke Podcast 166 is available for download: 

http://soldersmoke.com/soldersmoke166.mp3 

Bench Report:  Pete working on Direct Conversion Receivers.  
Bill on his 2B and on 20DSB rig, and an M0XPD/Kanga DDS kit, and a 140 watt amp. 

GETTING STARTED IN HOMEBREW:
Start simple:  Build an oscillator. Make it oscillate!
Gather tools, simple test gear, and books. 
Try to understand what you build. 
Build a direct conversion receiver.  
Don't fear the toroids! 
Be patient.  This is not Plug and Play. 
Build a DSB transceiver. 
Little tips: 
Protect variable caps. 
Use heat sinks. 
Use reverse polarity protection. 
Don't breathe the solder smoke! Ventilate your bench.

China Radio International Mystery Solved.  
Book Recommendation:  "International QRP Collection" by Dobbs and Telenius-Lowe
MAILBAG

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Sines, Squares, Harmonics, 'Scopes, FFTs, and Sounds

Bil Herd of Hackaday did a very nice video on Sine Waves, Square Waves and FFTs.  This is, of course, an important part of understanding how mixers mix.   I look forward to his upcoming video on Direct Digital Synthesis.  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Hunting for Sprites

Don't let the comments about "positive lightning" and "gravity wave" cameras turn you off -- in the world of meteorology, these terms seem to make sense (but I had to do some Googling).  The New York Times article on this topic is very interesting: 

http://www.nytimes.com/2014/09/30/science/on-the-hunt-for-a-sprite-on-a-midsummers-night.html?_r=0  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Beautiful Pictures of Mars from India's Spacecraft

Congratulations to the Indian Space Research Organization.  They put a spacecraft into Mars orbit on their first attempt, and they are getting back some spectacular images.  

I also like the banner on their web site: 

More info here: 

http://www.isro.org/pslv-c25/Imagegallery/mom-images.aspx

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Don't miss Thomas and his Minima at Pacificon!

Thanks for the kind words Thomas.  Be sure to have someone do a video of your presentation.

You truly have The Knack -- proof of this is your reaction to your wife's departure for field research in Senegal:  "IT'S SOLDER TIME!"  That's the spirit! 

Too bad about the chickens, but hey, they died for a good cause... 


Dear Bill,

I have been listening to your podcast for about a year now. I think you were right to say that one episode a month is a reasonable limit to avoid listeners getting addicted. At some point in January I was listening to you every morning and every evening in my car, a very serious case of addiction.

This is also the time that Farhan chose to announce the Minima and my wife to go to Senegal for 3 months for a field study (she is doing a PhD in Sociology). I think it took me less than a week to run to the shop, get most of the parts and start melting solder!

In two weeks from today I will present the project and my build at Pacificon. I would really appreciate if you could mention this on your blog because I am sure there are other listeners who will be there and curious for some homebrewing-materials. I hope to delight them!

For your own pleasure there are some pictures and videos on my blog: http://www.sarfata.org/ham/minima/ 

Pacificon Schedule:  http://pacificon.org/ (My talk will be at 10:45 in the Portland room)

My presentation will retrace my journey building the minima. From the first smokes on the crystal filter when I was not even sure how to test it, or what results to look for ; to the amplifier where I am still battling some oscillations (by the way, if you had not talked so much about them, I would never have understood what was going on!).

This project has taught me that radio is a lot less black magic than I thought. It bridged the gap between the maths that I can understand but not really "see" and the sound coming out of the amplifier. It made me realize that once split into stages, a radio is much better understood and testable. Without a doubt, this has been my most ham-enriching experience and I hope to convince more people to build a minima, preferably Manhattan style! 

(In this public setting, I will probably not discuss killing chickens to exorcize my amplifier but I thank you for the tip ...)

I got pulled back from homebrewing by life and work this summer but I kept the last three episodes of Soldersmoke on my phone. They were my safety parachute and I listened to them last week on the way home to give me the extra boost that gets me to melt solder or fix bugs until 3 in the morning on a tuesday. I don't think I will ever be able to express my gratitude for all that I have learnt reading the book and listening to you but I would like to start here: Thank you!

Please keep the podcast going! I have really enjoyed the new format with Pete. 

73,
thomas
kk6aht / f4hdq


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Let's Build Something! (Video) Part 1

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Radio China International Echo Mystery SOLVED!

For the past month or so I have been wondering about a strange echo that I've been hearing on the 31 meter transmissions of Radio China International.  I first noticed it on my "Kings Speech" regen receiver.  Then I heard it again on my "Off the Shelf" regen.  

For a while I thought that what I was hearing was a propagation effect:  Perhaps the very strong RCI relay station in Quivican,Cuba was sending north a signal so strong that it was travelling around the earth along the grey line and coming back to me about .133 seconds after the original reception.  

This sounded plausible (and it does happen sometimes).  But there were reasons for skepticism: Why wasn't anyone else hearing this?  Why wasn't the effect showing up on signals from Radio Havana Cuba?  

Pete Juliano had suggested that perhaps I was getting signals from TWO different RCI transmitters.  I had quickly checked the RCI schedule and didn't see them transmitting on the same frequency at the same time from multiple transmitters, so I kind of put that idea aside.  Hey, the round-the-world idea was just more appealing! 

But then I remembered something strange about the echo:  It seemed to disappear when I tuned close to the center frequency of the RCI signal, but then appeared when I tuned off to one side. Hmm.... That was an important clue. 

I've long been wary of regen receivers and for a while suspected that I was dealing with some weird regen effect.  Regen and Echo seem to go together, right?    Well, as it turns out, no.  But I was right about this being an effect of the nature of my receiver... 

Last night I was listening to RCI English service at around 0030 UTC on 9570 kHz.  Nice clear signal.  No echo. 

At 0100 UTC the program changed, and the echo started.  A very strong echo. 

I went to the RCI schedule.  Here I found the answer: 

At 0030 they were transmitting from their relay station in Cerrik, Albania on 9570 kHz. 
At 0010 they switched programs, frequencies and transmitters.  At 0100 Cerrik shut down, but the Quivican, Cuba relay came on on 9580 kHz.   At the same time the RCI transmitter in Kasi Sabagh in far-off exotic Western China, in Xinjiang, fired up on 9535 kHz.  Both transmitters were carrying the RCI English service. 

You see, my little regens are not very selective, and the RCI transmissions are quite strong.  So if I have my receiver tuned to around 9560 kHz, I'll be hearing BOTH the signal from Cuba AND the signal from Xinjiang.  That would explain the echo. 

To try to confirm this, last night I fired up my old Hammarlund HQ-100 receiver to see if I could discern the two different signals.  I could.  And the echo appeared when I tuned BETWEEN the two.  You can hear this in the video above. 

There is one remaining question here:  Is the echo caused by the RADIO path difference between the two transmitters?   Or are we just seeing the effect of the programming being transmitted at slightly different times, perhaps with this delay caused by INTERNET latency?  Anyone know how RCI gets its signals from its Beijing studio to its distant transmitters?   I calculate that the path difference is about 10,000 km.  With c at 300,000 km/second, that would yield an echo of only about .03 seconds.  The echo we are hearing sounds longer than that, so I suspect we are hearing a difference in studio-transmitter transmission time.  What say the SWL RF gurus?

BTW:  I think the same phenomenon may explain the echo on Brother Stair's "Overcomer" signal.  I see that starting at 2200 UTC he is on BOTH 7570 kHz and 7730 kHz from RMI transmitters in Florida.  Perhaps they are not synched up. 

I think this is all very cool.  Think about it:   Here I am, sitting in Virginia in 2014, listening to the Albanian, Cuban, and Xinjiang relay stations of Radio China International on a receiver first built by some guy in England during the 1930s.  And I'm trying to figure out if the echo I hear is caused by the limits imposed by the speed of light and the size of the earth,  or by the time it takes packets to move through sub-oceanic fiber optic cables.   

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Making Hardware for Mars in a Lab in New York City

I liked this video about building hardware for a Mars mission at a lab in New York City.

http://www.sciencefriday.com/video/08/10/2012/building-for-mars-sometimes-painful-always-glorious.html


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

The Amazing Apollo Board from Carbon Origins

Wow, lots of possibilities here....

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Arduino Makes Music with Old Floppy Drives

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A Beautiful BITX20 from PA1ED

Edwin did a beautiful job on his BITX.  This is an excellent example of stage-by-stage construction. 
This is his THIRD BITX.  On the second one he got all the parts from an old television and a washing machine.  That's the true BITX spirit!  
I want an S Meter!  
There is more information on his blog:
http://pa1ed.blogspot.nl/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

The SWLing Post, Ears To Our World, and the HumanaLight

Thomas, K4SWL, has a really impressive shortwave listening blog.  Yesterday he was kind enough to post an article about my latest obsession:  the echoes on China Radio International: 
http://swling.com/blog/ 

Even more impressive is Thomas's work on behalf of poor people in the Third World. He is the Director of Ears to Our World, a charity group that provides innovative, simple and appropriate technologies to schools and communities in remote, rural and impoverished regions of our world.
Here they are: http://www.earstoourworld.org/

They distribute radios to people who would no other regular technological contact with the rest of the world.  They are also involved in an intriguing project called the HumanaLight:  "Dead" AA batteries power lights that can make a big difference for people living in areas that have never been on any grid.   Here it is: http://www.earstoourworld.org/humanalight/

Ears to Our World is looking for Donations to help them bring light and radios to people who really need them:   Here is where you can help: 
http://www.earstoourworld.org/donate

This is clearly a very appropriate charity for radio amateurs. 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Inducted Into Shortwave Rogues' Gallery

Jeff Murray, K1NSS, has done me the honor of placing me in his VERY ELITE Friends of Shortwave "Rogue's Gallery."  Check it out:   http://dashtoons.com/FOSW.html

Kind of ironic that I should be recognized for my work on regens! 

Thanks Jeff! 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20