Flea Market Find -- Pi Net Tuner -- With a Mystery

Last Sunday's "Flea at Trastevere" (I'm the only one who calls it that) was a huge success for me. Minutes after arriving, amidst all the junk, Billy and I found this homebrew Pi network antenna tuner. The guy who sold it to me told me he had built it himself. The workmanship is top-notch. The quality of the parts is superb. There's a built in SWR meter and a 10 db attenuator.

When I started drawing out the schematic I noticed something weird: As the front panel indicates, it is a Pi -network, but for some reason the builder has the input variable cap floating. The physical connection to the chassis is via insulators. The other variable cap has the standard mechanical and electrical connection to chassis ground. That input cap needs to be grounded too, correct? Why would this builder -- who obviously knows his way around a soldering iron -- go to the trouble of allowing that input cap to float?

"Space Hackers" removed from YouTube

They say the videos were taken down because of some Intellectual Property issue. That's their story, but I've seen the X-Files, and know that something more sinister is probably at work here. Kay, WD0BDK, suspects the Russians -- the thinks they are mad at us for making fun of the Woodpecker!

(Note to lawyers: I did not post the videos on YouTube.)

Skepticism about "Space Hackers"

Many of us really enjoyed those videos about the two Italian brothers from Turin and their homebrew space monitoring program. But there is some controversy about some of their claims:

http://www.svengrahn.pp.se/trackind/Torre/TorreB.html

Controversy or no controversy, I still liked the videos and admire the efforts of the two intrepid brothers from Torino.

SolderSmoke #92

The latest SolderSmoke podcast:

http://www.soldersmoke.com

September 28, 2008
TOPICS:
The Flea at Trastevere
QRSS 2N2222 goes toes up. Why?
Da Vinci Code MEPT Frequency Standard
Wind Powered QRSS
QRSS Whispers reflecting off airplanes
Transformer troubles at CERN
Arnie's cool Cuban hack
Woodpecker update
A SolderSmoke charity project
Another engineer joke
Kanga USA BACK IN BUSINESS!
The Joy of Fixing Things
Jim Severns - KNACK VICTIM
A Homebrew Italian Space Program
MAILBAG: G0FUW in Gibraltar
VU3RDD in Southern India
KB1QVO on laser comms
K4BVL likes our audio
VK3PB on Italy's "Space Hackers"
W0DAB on free online MIT courses
DL4MGJ on fixing 2B parallax
WB6NTL on transistor failure mode
AF6C on crystal ovens
G3ZTB likes Shep

A Homebrew Italian Space Program

Peter, VK3PB, alerted me to the six YouTube videos about the Judica Cordiglia brothers of Turin, Italy. These guys were young and enthusiastic amateurs when the space race began in the late 1950s. They quickly developed some very impressive monitoring facilities that allowed them to listen to both US and Soviet space missions.

Watch these videos and you will not only get a look at the technical work of these intrepid and skilled amateurs, but you will also get a sense of the many intangible things that make Italy such a special place. You'll get a sense of the human warmth, the friendship, the enthusiasm and fun that characterize life here.

They had the foresight to film a lot of their youthful technical adventures. The videos take us back to the Italy of the late '50s and early 60's. (That roof that they built their antenna on looks EXACTLY like mine!)

Don't miss these videos. They are really wonderful. Here are the links (if you have trouble, just search YouTube for "Space Hackers 1/6" "Space Hackers 2/6" etc.

http://www.youtube.com/watch?v=1F_67UAaG70
http://www.youtube.com/watch?v=N-y2DuYNxm4
http://www.youtube.com/watch?v=s8sElZpvzRU
http://www.youtube.com/watch?v=wcGPXZPYHNs
http://www.youtube.com/watch?v=A9kiSMcrqRg
http://www.youtube.com/watch?v=WUT-eZH0860

Rudy Severns

Allan, WA9IRS, sent me the link to a really interesting article about guy who is obviously one of us, a victim of The Knack. Here is how the article begins:

An innovator in power-supply design who anticipated the trend toward higher frequency switching, an illuminator of power-supply topologies, and one who introduced many engineers to the promise and perils of power MOSFETs, Rudy Severns has made diverse contributions to the power electronics field in a career spanning five decades as an engineer, author, instructor and consultant.

On the 50th anniversary of his first jump from a biplane, Rudy Severns went skydiving yet again, pushing his lifetime total to somewhere in the vicinity of 500 jumps. Throughout his career, he took breaks for months-long sailing voyages, which usually necessitated a job change on his return. When it was time to fulfill his military obligation, a young Severns parlayed his experience as a radio operator into a stint with the Army's Special Forces, where he learned the skills of unconventional warfare.

Here's the link to the article: Rudy Severns

IZ1KXQ's Wind-Powered QRSS Beacon

Paolo, IZ1KXQ, is the fellow who brought us the 5 mw QRSS MEPT beacon powered by small solar cells (see an earlier blog entry). He is now experimenting with wind power. FB Paolo! We hope to see your windy signals soon.

Cool Cuban Hack

Arnie posted this on QRP-L. I thought it was a pretty ingenious way to work around
an unavailable part. FB Arnie!

My TS820 non QRP, but capable of QRP operation transceiver. ... has a similar type of female 9 pin socket to connect or not connect the external VFO. I needed a plug when not using the external VFO, and it was made using a Russian 6H2P dual triode that had a bad filament... I very carefully broke down the glass using nichrome wire at red hot temperature and then a thermal shock. The glass bulb broke nicely in a rounded even circle !!! Then I proceeded to remove the soldered connections to the two triodes... removed them , and soldered the wires required for the jumpers as specified by TS 820 manual... After checking that all was OK, then I poured Araldite epoxy to fill the glass ... It worked very well, and the only cost was the small amount of valuable epoxy ( not easy to find locally, and extremely useful for repair jobs and pasting the islands of the Manhattan style homebrew printed-nonprinted circuits !!! 73 and DX Arnie Coro CO2KK

Beacon Final Amp Goes Bad

All of a sudden the power output meter on my 30 meter beacon (MEPT) transmitter stopped jumping up and down. The oscillator was still running, and the keyer was working, but output had obviously dropped considerably. I started troubleshooting and my attention started focusing on the 2N2222A in the final. The stage runs Class A, with long QRSS key down periods. The emitter resistors get a bit warm. I replaced the transistor with a new 2N3904 and -- BINGO -- output was back up in the tens of milliwatts.

I did some tests on the 2n2222A. With a VOM I looked at forward and reverse bias resistance across both junctions, comparing the part from the rig with a new part from the same batch. In the transistor that went bad there is a lot more reverse bias current across the base-collector junction.

So, what happened? Any ideas?

This was one of those very satisfying repairs in which you quickly zero in on the problem, change one part, and then put the gear back into action. The victory was made even sweeter, when, a few minutes after I put the rig back on the air, I noticed my QRSS CW signal on I2NDT's online grabber.

I'm almost finished with my 10.140070 frequency standard. Armed with that, I'll be free to experiment with FSK keying (without fear of being unable to find my way back to the 100 Hz -wide QRSS frequency band). 73 from Rome

SolderSmoke #91 STEREO SPECIAL

Be sure to listen to episode 91 of the SolderSmoke podcast:

http://www.soldersmoke.com

September 14, 2008

TOPICS:

Sardinia!
ON5EX's QRSS MEPT leads us back to bike riding
Watching Jupiter, listening for Jupiter
KF6KYI's I-tunes QRSS
Stan, 9H1LO's new grabber
Laptop motion detectors as earthquake detectors
Nuclear fusion in the shack
Philo T. Farnsworth
Building a QRSS freq standard
SPRAT CD
Forget about stocks: SSDRA now selling at $399.89
SolderJokes
QST articles on-line! FB!
Jim Williams and the joy of fixing things
STEREO SPECIAL: Roger Hayward's new binaural DSB project
Antenna woes
MAILBAG:
G0WAT on HOGCON 2008 (21 Sept in Herts.)
AJ8T on Russian rovers with laser reflectors
KA9OOI on language and low pass audio filtering
WB6TNL says NO to rat neurons in QRP gear
KB6QR "beknacked" vice "knackered" ?????
NR5A has a Drake 2A
7J1AWL on the air from Vietnam
KC0PET goes solar
OZ1CJX Bad case of Knack, may need professional help
K8WPR says Knack keeping him away from wild women, bars
AJ8T on CK722 museum
AG5RS works Texas balloon from Dubai (via net)
KI4SGU POW radio parts
N8WQ on schematic drawing program
KF4LMZ has QRSS-itis, finds 10.140 rock in CB rig

The Joy of Fixing Broken Gear

Alan, WA9IRS, sent in this really great link about Jim Williams, an engineer who writes for EDN. In his article Jim captures better than anyone the joy of repair.

Those taking up an engineering degree online can use the tips included in his book.

Check out his article: "Try Fixing it Yourself."
And if you like the article, check out Jim's book: Another Look at Analog Circuit Design

N2CQR in Sardinia

There was no SolderSmoke podcast last Sunday because at our normal
broadcast time we were on an overnight ferry from Rome to Sardinia.
Beautiful island! I have a little SW rx with me, and this
Blackberry. And SSDRA.... But not much radio work this week.

Stars are beautiful here. Milky Way is BRIGHT! View was especially
good from the ship when we were way out in the Med. 73 from Sardinia!

Bill

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