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Sunday, January 6, 2013

Move over Altoids Tins! Legos for Raspberry Pi Case

Too bad the Raspberry Pi board is a bit too big for our beloved Altoids tins.  It would have been a very fitting match:  British board in a British box.   A twelve year-old has solved the problem with Legos:  http://blog.makezine.com/2012/06/11/lego-raspberry-pi-enclosure/
Will this lead to raids on the toy boxes of the grandchildren of SolderSmoke fans? 
Billy's RasPi is running nicely (but no Legos for him).   

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

Saturday, January 5, 2013

Signal Generator Ideas


Hi, Bill

Howzabout a generator that goes from 1 Hz to 40 MHz with 1 Hz resolution, adjustable cursor so you can step any of the 8 digits, presettable offsets for if frequency, repeater offset, or r.i.t., directly synthesized output so almost no phase noise and 12 bit waveform accuracy? How about a price tag of less than $20 for all the major parts? Start by Googling dd_synth.asm for control software, and rather than buying the PCB recommended in the notes at the head of the program, search for AD9850 on Ebay for the synthesizer board and LCD 16x2 for the display. A 16f628a PIC is a couple bucks. Both the display pinout and the synthesizer pinout match standard perfboard. For a little more than $10 more get the AD9851 board and the upper frequency limit is 60 MHz.

A better way to transistorize the old tube-type generator is to use a dual-gate RF mosfet for the oscillator. You can trim the gain for waveform purity by adjusting the bias on gate 2. Once you find the optimum bias on each band, diode-switch the bias level with the bandswitch. Since gate 2 has an extremely high impedance you can use resistors in excess of a megohm, so it won't affect the Q of the tank coil.

Jim Daldry
Raleigh NC


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

Friday, January 4, 2013

Opening Scene of Contact (CQ at the end)


Mike Herr's video on his use of an Arduino to call CQ SKN made it onto Hack-A-Day 
yesterday and provoked some discussion there of the meaning of CQ.  One fellow posted 
this opening scene from the movie Contact.   I thought you guys would like 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

Thursday, January 3, 2013

Arduino Does Straight Key Night




Bill,
     Hope a good Christmas and excellent New Year. Here at WA6ARA we had a blast for Straight Key night . In the past I have used new keys, old keys and multiple keys. This year we celebrated SKN with a little twist. At Pacificon I purchased a hugh CW key, all made out of wood, about 3 times the normal size J-38. This isn't a QLF key but a piece of beautiful wood working, and fully functional. This was my main key for SKN.
But SKN can require the sending of CQ SKN for a considerable amount of time. Normally a programed keyer would do the job fine. But this is not in the true spirit of SKN, the use of the straight key. So, using a trusty Arduino board and a few lines of programming,  I solved the practical and ethical problem. The Arduino drives a model airplane servo. The servo is positioned such that it's arm presses down on a miniature J-38 key, thus sending the "CQ SKN". Also the miniature J-38, about half size, sort of balances out the larger size of the
hand key, and keeps the universe in check. I've enclosed a short youtube for your viewing enjoyment

http://youtu.be/Rn7Ky9Ib7ug

73
-- 
Mike Herr
WA6ARA
DM-15dp
Home of The QRP Ranch

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

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! 

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

Tuesday, January 1, 2013

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 s
ounding 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
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