Pumpkin Pi and JBOT Gremlins

Maria wanted to go with a mathematical theme for this year's Jack-0-Lantern. Pumpkin Pi!

I have been chasing some gremlins and banshees around my old Azores 17 meter DSB rig. The JBOT Amp worked fine into a dummy load, but of course things got a bit more complicated when I put it into the rig and connected it to an antenna. It would take off (like a banshee!) if the load was at all reactive. I think this is the result of inadequate shielding and inputs a bit too close to outputs. But it all settles down nicely when I put a transmatch in the antenna line and tune out the reactance. I may just leave it this way.

Output is a bit low -- only about 1 Watt. I realize that at 18 MHz output should be dropping a bit, but I think I should be getting more. I THINK I'm giving it the recommended 1 milliwatt input. At some point I think Farhan mentioned the possible need to experiment with the number of turns on the secondary of the output transformer....

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

Snow Static

Related to our post about my new (old!) all-boatanchors heating system (see below), yesterday I had some really horrendous static. I think it was caused by the snow. A Google search on "snow static" brought me to this video (which Gregg in Finland found "shocking""). I liked the tuner and the neon bulbs too.

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

My New Shack Heating System: Heath, Halli, Hammarlund and Drake

Temperatures dropped over the weekend and I had to fire up my new heating system for the SolderSmoke shack. See above. Heating by Heath, Halli, Hammarlund and Drake (sounds like a law firm doesn't it?). I'm happy to report that those old filaments take the chill off quite nicely while adding a nice aroma to the room, along with some very pleasing lighting effects (I especially like the green glow from the DX-100 tuning dial).

The Azores-17 DSB JBOT project is (I think) complete. And I did include a low pass filter. In keeping with the finest of ham radio traditions, now that it is cold I will go out and work on an antenna.

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

Another Treasure Trove: The Royal Society's Archive

I'm a big fan (wanna-be really) of The Royal Society. In SolderSmoke 138 I noted that Isaac Newton (former Society president) seems to have had The Knack. And when I was in London one of the major perks of my job was that I occasionally got to visit the Society's headquarters. Bill Bryson recently edited a book about the Royal Society -- in his intro he noted that they have always been a very international group (just like us!)
Several readers wrote in with the happy news that the Society's 350 year archive has been placed on-line. Here it is:
http://royalsocietypublishing.org/site/authors/free-archive.xhtml

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

Homebrew Jet Engine from Junkbox Parts!

Bob, W8SX (our man in Dayton) sent me this nice video. I really liked the friendly and enthusiastic way in which the builder described his project. I only wish he would have fired it up! Thanks Bob!

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

Azorean Oscillator Re-build

With my JBOT amp ready for installation, it was time to go back and check out the rest of the circuitry on my old Azorean DSB/Direct Conversion 17 meter "Magic Carpet" transceiver. I was surprised to find that the oscillator, well, wouldn't oscillate. The MPF102 that I had in the main oscillator circuit was blown. I suspect voltage spikes from the T/R relay. I installed the required diode across the relay coil. (I seem to blow up a lot of MPF102s. Is it just me, or are these devices really fragile? They are junction FETs, not MOSFETS, so I thought of them as being more robust. But I seem to go through a lot of them.)

After messing around with the oscillator and buffer circuits, the nice clean Manhattan isolation pads that had been there at the start were all messed up, with big piles of solder with the ends of multiple axial leads stuck in there. I decided to start afresh. Out came the little PCB box that housed that housed the oscillator, buffer and amp stages. Off came the walls of the box. (When I built this thing the first time, I didn't realize that I would need an amp to get to the 7 dbm needed to drive the diode ring. I ran out of room on the main board and ended up building the needed amplifier on the back wall of the box!)

So I got to build this little circuit again, ten years and three countries after the original build. It was fun. I like building oscillators. There is that satisfying sense of closure and completion when, at the end of the effort, you turn on your receiver and hear the tone from your creation.

There was also a fun little bit of troubleshooting. After rebuilding the oscillator circuit I noticed that applying power to the "on the wall" amplifier caused the oscillator to shut down. At the buffer, I was seeing RF in and RF out, but the whole thing would shut down when I powered up the next stage. Obviously there wasn't a lot of BUFFERING going on! Sure enough, the MPF102 was bad. I replaced it from my dwindling supply, and all was right with the universe.

Now the amp goes in. But first I will build the low pass filter. I promise.

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

Steve Jobs (age 12) calls Bill Hewlett (of HP)

"When he was in eighth grade, Steve Jobs decided to build a frequency counter for a school project and needed parts. Someone suggested that he call Bill Hewlett. Finding a William Hewlett in the telephone book, the 12-year-old Jobs called and asked, "Is this the Bill Hewlett of Hewlett-Packard?" "Yes," said Bill. Jobs made his request. Bill spent some time talking to him about his project. Several days later, Jobs went to HP and picked up a bag full of parts that Bill had put together for him."

More HP stories: http://www.hp.com/retiree/history/founders/hewlett/quotes.html

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