Like a Hamfest, but kind of EVIL

For a look at how the hackers do their version of the Dayton ham-vention, check out this video on DEFCON:   http://vimeo.com/56234900

Looks sort of like "Four Days in Hell" to me!  Finally, a group that makes hams seem normal and well-balanced! 

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A Nice Hallicrafters S38-E Knack Story

Bill - 

It was Christmas of 1958 (5th Grade)that my parents bought me the Hallicrafters S38-E that I still have.  I was recovering from multiple surgeries the previous summer to correct for the effects of Polio when I was 3.  I came down with Polio in the last year before the vaccine was released to the public.  

A bit of bio - because of my physical limitations as a child, I spent a lot of time indoors reading and listening to the radio.  Broadcast AM here at that time was still playing dramas like "The Lone Ranger" and "Big John and Little Sparky".  I really enjoyed them.  Then, on that fateful day I asked my mother why, since our radio plugged into the wall electric outlet and we could hear people talking, weren't other people able to hear us talking on their radio if we spoke into the loudspeaker.  She said, 'I don't know, but the library ( 2 blocks away) will have books about radio that you can read."  The Knack bit early and it bit hard.  

By the time I was in 5th grade I had discovered short wave radio.  I dearly wanted a short wave radio and I wanted a Hallicrafters.  Somewhere I had found a catalog and wow! nothing else would do.  What I didn't realize until I was in my teens was just how hard times were for my folks.  Most families then did not have medical and hospitalization insurance.  My dad was paying off the hospital and the doctors every month almost until I graduated from high school.

But, anyway, I did get the S38-E for Christmas.  At $69.95, it was the least expensive Hallicrafters available.  In reality, it is just an All-American - 5 with extended tuning range.  Tuning was as broad as a barn door, and above 15 MHz it is as deaf as a post.  But it was mine and I loved it.  The short wave bands were still hot in those days as we were just peaking through one of the most celebrated Solar Maxima of the last century.  Many the hours I listened to HCJB - Quito, and Radio Moscow, and Voice of America....   I also found people talking to each other - Wow!  Ham Radio.  And just look at me now.... And those strange beeping sounds - that was actually people talking? And what was that strange Donald-Duck sounding talk all about?

Yes - I still have that same S38-E.  It went to college with me, and has been with me for over half a Century, now.  Yes, it still works. (Needs a replacement IF transformer),  Yes, it will shock the bejeebers out of you if you plug it in wrong.   {I use two filament transformers back-to-back to prevent that.)  Yes, the Knack still has me, but that's another chapter.

72's 
Bruce  KK0S

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

High Pitched Audio QRM in SS #148

Two listeners blessed with good high frequency hearing alerted me to the fact that the latest podcast had some annoying high pitched noise in the background.   Peter, VK2TPM was the first to report it -- he sent along the above spectral analysis of a gap between words.  Steve,  W1KF,  also heard it, and provided a clue that I think solved the mystery.  

Steve noted that the noise was not present during the sponsor ads that were included in this episode. 
That let me figure it out.   On Saturday when I was recording this,  I got through about half the show when the power went out (that happens a lot here).  The battery in the laptop I was using to record the podcast saved the day and no data was lost.  The power came back on within a few minutes, but the outage had turned off the main PC in the shack.  That PC (AND ITS FAN) remained off when I was recording the ads.   I did the same kind of noise removal processing that I always do, but this time the noise sample that I used was taken from the mic with the main PC (AND ITS FAN) turned off.  My guess is that the whine from the fan (which I can't hear due to tinnitus) didn't make it into the noise sample, and thus didn't get removed from the podcast audio.    I went back and did a couple of rounds of noise removal and low pass filtering.  I think (I HOPE) I got rid of the offending noise. 
I have uploaded a new and hopefully improved version of the podcasts.  Audio reports will be appreciated.   

One of my New Years resolutions is to improve the technical and substantive quality of the podcast. 

Thanks Peter, Thanks Steve. 

Happy New Year to all! 
  
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 #148

SolderSmoke Podcast #148 is available:
http://soldersmoke.com/soldersmoke148.mp3
December 30, 2012

SPONSORED BY usedradiomall.com

-- Hurricane Follow-up
-- Subliminal Mind Control to Encourage Homebrewing (beep-beep)
-- The Shortcomings of the All American Five Receiver
-- Solid-Stating a Heath SG-6 (with Farhan's circuit)
-- VK3YE's Beach DSB Rig
-- Tek 'scope connection to frequency counter
-- Mod to W7ZOI/W7PUA power meter
-- JBOTing my 20 meter DSB Rig -- A Tale of Woe
-- LU1AR "The Most Interesting Ham in the World"
-- Billy's Raspberry Pi
-- Latest QST, SPRAT, Hot Iron
-- Videos: Landfillharmonica,  Knack in Sierra Leone
-- Santa delivered a Soldering Station
-- MAILBAG

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

He Should Have Used a Low Pass Filter!

http://www.sun-sentinel.com/news/broward/hollywood/fl-pirate-radio-hollywood-20121229,0,5142922.story

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

A Christmas Present from Argentina

There is an old saying in Spanish:  "No hay mal que por bien no venga."   More or less this is the same idea as: "Every dark cloud has a silver lining."  Well, the dark cloud was my techno-agony with the parasitic oscillations (see below).  The silver lining was the e-mail from Edgardo, LU1AR, in Buenos Aires that helped me get rid of them.    Edgardo advised putting a resistor across the primaries of the JBOT amplifier stages.  This is an old "lower the Q" trick, the idea being that lowering the Q might help prevent the amp from self-oscillating.     I used 680 ohm resistors.   First I put one across the primary of Q1.  No joy. Then Q2.  No luck.  Then I put one right across the primary of that big output transformer.  That did it!  The parasitics disappeared.   And I still get a nice 4 watts of output.  Thanks Edgardo.  I hope to make a contact with this rig today. 

The real silver lining in this story comes, however, in the form of Edgardo's blog site.  Wow, what an inspiring example of Argentinian Knack.  Radios, telescopes, auto-giros.  This guy is also into homebrew DSB rigs.  Wonderful stuff.  Check it out.  (Google will translate it for you, if necessary, but even if you don't read Spanish, the pictures tell most of the story.) 
http://www.lu1ar.blogspot.com.ar/
Thanks to all who sent advice and encouragement.  Merry Christmas! 

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

Woe is me! Why Podcast is Late: Parasitic Oscillations!

I'm building my FOURTH JBOT and this one is giving me more trouble than all the others combined.  
Here are the details of my tale of woe:
20 meter rig.  Double Sideband.   The JBOT is fed by a simple two-diode, trifilar toroid singly balanced modulator.  NO DIPLEXER TO SPEAK OF.  At the output of the balanced modulator there is a 1000 uH choke to ground and a .001 uF cap to the input of the JBOT.  AF amp is an LM-386.  VXO is a very simple MPF-102 one stage ceramic resonator VXO with no buffer stage.  7 element low pass filter (three coils, four caps). 
All the transformers are wound on FT-37-43 cores.  T3 is four such cores stacked 2X2.
 
The arrangement works beautifully into a 50 ohm dummy load.  But as soon as I connect it to an antenna (a dipole out in the yard, fed with 50 ohm coax) the output signal gets ugly.  
Looking at it on the scope, instead of the nice figure eight pattern (similar to the two tone test pattern of SSB) I get ugly fuzzy outcroppings from the peaks.  Looking at the signal more closely I can see that in addition to the 14.2 Mhz signal, there is another LF oscillation at around 250 kHz. 
I've been struggling with this.  I can't get rid of the LF oscillations. The leads are all short and the inputs are far from the outputs.   I've beefed up shielding, and decoupling.  I've sacrificed a chicken to Papa Legba. Nothing seems to help.  
I THINK the feedback/oscillation is taking place in the JBOT itself -- not through the
audio amp or the balanced modulator or the VXO.
I watch the RF and the AF inputs to the balanced modulator to see if there is any difference between the stable situation (with the 50 ohm dummy load) and the unstable situation (with the antenna),  I don't see any differences. 
I even put an antenna tuner between the final and the antenna anb made sure that the antenna looks like 50 ohms non reactive.  This seems to help a bit, but the ugly instability is still there. 
Help me! 
\

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

LadyAda Named Entrepreneur of 2012

Watch this video and you will see that Limor Fried has The Knack!
She and her company have brought homebrew electronics back to lower Manhattan.
Some kind listener sent me a gift certificate for Ada Fruit.  We will put it to good use, probably
with Raspberry Pi and Arduino gear.
Three cheers for Lady Ada!

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

Roadkill Violins! LandfillHarmonic

Landfill Harmonic film teaser from Landfill Harmonic on Vimeo.

Wow, this is a really inspiring video about being inventive, overcoming obstacles, using what you find and putting junk to good use.  I thought you guys would like this (ESPECIALLY ROBERTO!).

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

FITSAT-1 Flashing Morse With LEDs from Orbit

Very cool:  Japanese students sent up a small satellite.  One of its capabilities is to flash Morse code messages in the visible light range using LEDs.   Prepare to peg your geek meter: 
http://www.fit.ac.jp/~tanaka/fitsat.shtml 

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

PE1JXI's BITX-20 Handheld

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

Watching a Light Beam at One Trillion Frames per Second

Billy alerted me to this TED Talk presentation on an MIT Media Labs project that used new "femto photography" techniques that allow us to watch -- in VERY slow motion -- a light beam pass through a bottle. Amazing. Makes me think about Einstein's old thought experiment about running alongside a light wave (but of course here they are slowing down time...)

 Here are some details on how they did this:
 http://web.media.mit.edu/~raskar/trillionfps/ 

 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