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Tuesday, January 12, 2010

AA1TJ: Reggies Rule! Diode Amps! QRP to the Max!



Whenever I find myself in need of some radio-inspiration, an e-mail from Mike, AA1TJ, seems to pop up in my inbox. This morning's message and the associated video (above) were especially inspirational. Mike was e-mailing Steve, WA1HFF.

Hi Steve,
Thanks for the message and the great QSO! I was running my one transistor transceiver that I call the Reggie. You can read about it on my webpage at

http://mjrainey.googlepages.com/reggie

My antenna is nothing to write home about; just an end-fed half-wave wire bent into an "EL" at 35 feet.

I've made just over 240 contacts with my Reggie in a little more than a year's time; working 19 states. My best (and only) real DX was the Bahamas. All of these contacts were made with no receiver gain on this end; just a pair of diodes fed by a one-transistor BFO, and onto the headphones.

A couple of fellows have built their own Reggies, so you might run into one on 80m now and then. I've made three Reggie to Reggie QSOs thus far.

Steve, last night I was trying something new; I ran a loudspeaker from an audio amplifer connected to my Reggie. What's unusual is that my audio amplifer was made from three, common power supply rectifiers (1N5401's). I'm not kidding! It's a nearly forgotten circuit from 1954 that I (re)stumbled upon a couple of weeks ago. It uses the phenomenon of PN junction charge-storage to produce amplification.

Last week I used two diode gain stages for a total power gain of 48dB to drive my headphones. Yesterday, I added a third diode gain-stage and connected it to a loudspeaker for shack-filling audio volume.

I made a video of last night's setup (the same setup I worked you with). You can see it at

http://www.youtube.com/watch?v=3DA07A6BLDg

Thanks again for the nice contact last night, Steve. You were armchair copy here! :o)

Best wishes,
Mike, AA1TJ

Here's a question for Mike: Can you build that kind of amplifier with homebrew point-contact diodes? If so, you'd be opening up the possibility of a homebrew solid state receiver with homebrew solid state devices. Oh man, this stuff makes me feel like such an APPLIANCE OPERATOR.

Homebrew SR-71 Blackbird (with real jet engines)

Monday, January 11, 2010

DXing with Crystal Sets

Mike Tuggle has an excellent article on this subject in the Antique Wireless Association's on-line archives of the "Old Timer's Bulletin. " Here's the link:
http://www.antiquewireless.org/otb/dxxtal.htm
The link for the Antique Wireless archive (another treasure trove for us) is:
http://www.antiquewireless.org/otb/archive.htm

Sunday, January 10, 2010

Our New R/C Electric Airplane

We are thinking that olive groves are not quite as forgiving as the corn fields that the kid in the picture is using. And the bit about "no experience needed" probably should have a "as long as you don't mind crashing." Oh well, I guess crashing is part of the learning experience. But a quick review of the pertinent R/C airplane forums reveals there may be problems with this wing design: Apparently when it stalls, one wing stalls before the other (i.e. it "tip stalls"), with catastrophic results. The plane has a very comforting ACT ("Anti-Crash Technology") feature, but the forums advise that this feature may cause more crashes than it prevents.

We have the plane back on the Rome workbench this weekend. Crazy glue and tape are being applied. We will be back out at Chinghale International Airport (i.e. a clearing in the olive grove) next weekend to see if we can get a few good flights out of this thing.

Radio notes: The radio control system is on 27.145 MHz FM.

Thursday, January 7, 2010

Stradivari, Violins, Sunspots, and the Maunder Minimum

I mentioned Antonio Stradivari in SolderSmoke 120, but I felt a bit guilty about it, because there wasn't much of a connection to radio. But Nick, KB1SNG, has come to the rescue. Nick sent me this interesting article that discusses POSSIBLE connections between the quality of Stradivari's violins and the sunspot count. Check it out:
http://news.nationalgeographic.com/news/2004/01/0107_040107_violin.html

A recent article in The Economist alerted me to the fact that OM Stradivari was busy in the shack, churning out mechanical audio oscillators well into his 90's. I thought that Stradivari's late start, and his success in his senior years makes him an inspiration for many of us. A quick look at the Strad-Wiki page confirms this: Stradivari didn't really hit his stride until age 54, and did his best work between age 54 and 81.

Wednesday, January 6, 2010

New antenna for the HW 8 station


Now that my HW 8 station has been moved indoors (good thing -- there was snow on the hilltops this week!) I had to put up a new antenna. I decided to go with the same design that I had earlier: a dipole fed with TV twin-lead. I knew I needed a bit more wire than I had used in the original -- I had trouble getting that antenna to tune up on 80. So I went to the local hardware store and asked for 20 meters of AC line cord. That cost me 8 Euros. Not bad.
We had a nice sunny afternoon on Sunday -- Billy and I took the line cord out into the olive grove and pulled apart the two wires. (Hint: Start from the center, and pull slowly, or else the cord will get all twisted and a two minute job will turn into a twenty minute exercise in untangling.) I got to use some of those Radio Shack "solder strips" -- I just wrapped a few around the connection points and applied heat from a cigarette lighter.
I put some parachute cord (550 cord) over a conveniently placed tree branch using the venerable rock and rope method. One throw was all that it took. The radio gods were smiling on this project.
Success! With the Trastevere flea market Pi network, the thing tunes up nicely on 80, 40, 20, and 15. I notice that the cheap CB SWR meter that also I picked up at the flea market doesn't seem to sample much RF at 80 meters. I'm guessing that the designers were very focused on 27 MHz.
I quickly worked stations all over Europe, and even worked one station in Israel. I worked G4OEC in Somerset -- I immediately thought of Tim Walford, and asked OM OEC if he knew the wizard of the Somerset farm. Mac said his village was far from Tim's QTH.
It is nice to once again get familiar with the daily routine of the bands. 80 is hopping when I turn the rig on at 6 am local time. 40 seems to be active too. 20 opens a bit later, and I can hear stateside stations starting around noon local time. I really like hearing KZ1H up there in the high end of the 20 meter band -- I can hear him almost every day.
Check out the ad for the HW 8 in a 1978 catalog. This must be a non-U.S. catalog because the ad brags of the HW-8's ability to "work the States."
Not much astronomy this weekend -- Sabina and most of the rest of Italy fell under clouds on Sunday night. But I did catch a glimpse of Capella and the Kids.

Saturday, January 2, 2010

SolderSmoke Podcast #120


http://www.soldersmoke.com

January 2, 2010
Olive harvest in Sabina, Christmas and New Years in Rome.
"What, no Klingon?"
How's my whistling SSSS problem?
DX on 20, HW8 QSO with KZ1H
Auroral flutter on US stations
W4OP: Homebrew Hero
Softrock progress
Linux woes
72 Part Challenge: "Stuck between best wishes and hugs and kisses!"
Chinese Hamsat in orbit, with CW telemetry
AA1TJ in CQ, and using diodes as audio amplifiers.
Stradavari and Julia Child: inspirational late starters!
Billy's RC plane
QRSS: telemetry next?
WSPR: 150K reports per day
New issue of Hot Iron
MAILBAG
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