Eclectic Electronics: Powering Arduinos with Tube Filament Voltage

You know that you are dealing with a broad range of technology when you find yourself discussing how to power an Arduino microcontroller from the 12V AC voltage on a vacuum tube filament line. Thanks Pete. 

Hi Bill,

There is only so much that can be said in 1 hour and 19 minutes so maybe here is some stuff for the blog.

The 1st thing on the list when working with the Arduino when it is not connected to the computer is to have a proper power supply. My research as indicated that 9 VDC “raw” is a good starting point to power the Arduino boards so here are two supplies that will provide that power.

I did find that it was necessary to have an isolated supply when working with the “toob” radios and even to isolate the RF into the radio using a ferrite core transformer –some more tribal knowledge.

One supply takes an 8 VDC regulator and boosts its output to 9 VDC. The second uses a switching regulator and the beauty of the second is that the input can be either 12 V AC or DC. This is ideal for use in toob radios where you can sample the 12.6 VAC filament string.

73’s

Pete

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

Regen Receivers in Cuba

Hola amigo Bill:

I was able to pick up the podcast with excellent audio quality.
It is quite true that regenerative receivers are very much in use
even today... for example many if not all of the automobile RF
keys opening and closing the cars doors rely on a superregenerative
receiver circuit !!!

The radio that you copied at the blog works very well indeed
but it would be  good idea to include a 5 kilo ohms volume
control.... Very easy to do indeed.

But let me tell you that my favorite regenerative receivers are
the classic ones, using vacuum tubes, and operating them
at voltages not higher than 50 volts... As a matter of fact many
tubes work very well at the 24 volts DC voltage level.
Using the classic Hartley circuit , there is no need for a hard to
find throttle capacitor required by the Armstrong circuit, because
the regeneration control works very well by using a potentiometer
to change the screen grid voltage of the detector.

I agree that using an RF stage ahead of the detector is always
a very good idea.... In my tubes regenerative I use a triode connected
6AK5 clone.... as a grounded grid stage....another 6AK5 clone ( the
6ZHE1P Russian tube ) is the detector and I use another 6AK5 clone
as the first audio amplifier then feeding an audio output pentode
all provided from a very simple basic 70 volts DC power supply.
BTW, using regulated DC on the filaments of the detector stage,
although a luxury by my standards is very helpful to reduce
hum .... 7805 regulator recycled from a bad motherboard, with
one 1N4007 from broken Compact Fluorescent Lightbulb inserted
in series with the regulator ground pin, produces a nice 5.7 volts
regulated DC that with a brand new tube is more than enough... with old
6ZHE1P recycled from Russian TV sets, you add another 1N4007 to obtain
6.4 volts regulated DC....

As said in the podcast, it is very important to do a very good
mechanical engineering job, place the main and bandspread tuning capacitors
away from the front panel, use isolated shafts between the capacitors
and the dial mechanism and make the front panel of a a thick steel
plate if possible.

There is a Dutch Cascode Regenerative radio that several Cuban radio
amateurs have built... it was designed with the amateur bands in mind so
the information about the tuning coils and capacitors lets you
obtain a very excellent bandspread on the ham bands.
I can send you that circuit that uses very common 12AT7-ECC81
and Russian equivalent double triodes.

Keep up the good work amigo and always tell us when the next
podcast is available. BTW it lasted for almost an hour !!!

73 and DX

Your amigo en La Habana, Cuba
Arnie Coro
CO2KK
Host of Dxers Unlimited radio hobby program
Radio Havana Cuba


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 #165 Arduinos!

SolderSmoke Podcast #165 is available: 

http://soldersmoke.com/soldersmoke165.mp3

September 13, 2014

Workbench Update:  Bill's "Off the Shelf" Regen,  Pete's Boatanchors
Mysterious Echos on Shortwave Signals.  Solve the Mystery.  Please. 
Microcontrollers -- What they can do for you.
Small world:  As a kid, Pete was neighbor of "Digital Dial" N3ZI 
NEWS FLASH: Arduino creator Massimo Banzi was a ham!  
Born in a bar, cheaper than pizza:  The Italian origins of Arduino
Arduino CW generators
No coding skills needed
Arduino + AD9850 = Signal Generator or VFO
Arduinos in the Minma
What the heck is a Shield?
SolderSmoke 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

Schematic for "Off the Shelf" Regen

Tony, VE7JUL, wrote in asking for a schematic on the "Off the Shelf" regen.  Here you go Tony.  Nothing fancy or new here.  All the credit goes to Howard Armstrong, Charles Kitchin and Jay Rusgrove! 

Even though they seem much simpler than other receivers, I think regens are in fact more of a challenge than, say, a Direct Conversion receiver.  Be prepared to do a lot of fiddling around with the coil and the tuning and regen capacitors.  Think of that detector stage as a VFO, a VFO that you want to be able to smoothly take out of oscillation. 

Here's a tip on regen debugging:  Once you have it built, hang a high impedance 'scope probe off the drain of the FET and watch the scope/counter as you move the main tuning cap and the regen control.  This will give you a visible indication of where (on the regen control) the stage is going into oscillation.  A freq counter (I have one inside my Rigol 'scope) will let you know what frequency range you are operating on.  You may end up having to make adjustments to the coil, adding or taking away turns to get into the proper frequency range, or to the desired level of feedback.  Pay attention to the phasing of the coil turns.  You may also find yourself adding capacitance in series with the regen and main tuning controls (to reduce their tuning range) or adding capacitance in parallel with the main tuning cap (to lower the entire tuning range if necessary).  

Build it solid and strong!  It is, after all, an oscillator.  Be prepared to do a lot of "noodling"   

Hi Bill,

This receiver with just 4 transistors and no chips looks really interesting to me.  Do you have a schematic that you could either flip to me or point me to?  Getting my hands on some air variable caps may be a challenge, but I can 'noodle' something out on that.

Love the podcast, blog and really enjoyed the SolderSmoke book - thanks for your continuing efforts to share with the amateur radio community.

73/72
Tony

VE7JUL

the little red dot at Coquitlam, British Columbia on what used to be the Clustr map (but is now a Revolver map)

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

Shortwave Echo Mystery on Yet Another SW Station. What is this?

A few weeks ago I noticed a strange echo on Radio China International's signal.  If you scroll down a bit you can see my YouTube recording of the problem.  On one of the SWL lists, there was speculation that this problem was the result of a flaw in the RCI digital studio gear.  But then a few days ago I heard it again on RCI -- surely the tech-savvy Chinese would not have let this kind of problem persist for weeks.  

Today I heard the same effect on a very different SW station -- this one an the 24/7 fire and brimstone broadcast that appears at many points on the dial.  The effect is very similar to what I heard on RCI.  

So OK all your shortwave gurus:  What is going on here?

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

"Off the Shelf" Regenerative Receiver

I call it the "Off the Shelf" Regen because the base on which it is built is scrap lumber from a recent shelf building project.  Also, all the parts came out of the junk box.  

6-10 MHz, AM, CW, SSB, Data.   4 transistors, no chips.   


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 Interview on ICQ Podcast

Colin and Martin of the ICQ Podcast were kind enough to invite me in for an interview.  I really enjoyed our talk.  We covered a lot of ground, everything from podcast history, to regens and BITXs and Arduinos.  I think SolderSmoke podcast listeners will enjoy this.  Thanks Martin!  Thanks Colin!  Here it is:

http://icqpodcast.com/download-the-show/2014/9/7/series-seven-episode-eighteen-bill-meara-n2cqr-07-september-2014


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

Ed's Awesome Workshop

Wow, there is a lot of workshop wisdom in this video.   This is also a reminder that there are a lot of very cool people in the FDNY.   Ed is an EMT/Firefighter.  

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

Arduino CW Sender by KK6FUT and N6QW

The next time Pete and I get together on SolderSmoke, we'll talk about Arduino.

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

Sometimes the Receivers Seem to Almost Self-Assemble

I've been building shelves for my wife.  So I end up with all these nice pieces of pine, just the right size for the base of a breadboard receiver and a very sturdy cabinet to surround it.   Then I find in the junk box two nice variable caps and this old pill bottle coil (with tickler!) that I wound in 1998; I figure they will resonate from around 5 - 15 MHz.  Then Jeff Murray, K1NSS does that poster about Dave Richards, AA7EE (scroll down) in which he mentions the virtues of a National Velvet Vernier reduction drive -- I have one of those too.  And then there is the copper-clad board (from AL7RV/W8NSA) that would be perfect for the front panel.  You see where this is going, right? My friends, I am once again on the road to shortwave regeneration.  It will have an Armstrong detector with throttle cap.   

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

Youth, Short Waves, and the Invigorating Properties of Regen Receivers

Oh man, when I saw this I just had to put it on the blog.  The artist is Jeff Murray,  K1NSS, the genius behind Dashtoons.   Dave Richards AA7EE is, well, the OC!  

So not only have we learned that regen receivers are NOT demonic, we now see that they have health enhancing properties!  Like all that antioxidant stuff!  This is great.  I'm feeling younger already.  

Regen on my friends!     

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

Cutting Edge Regens! No, really.

Bill - 

Thanks so much for featuring The Sproutie on your blog. I heard through my friend Jason NT7S on Twitter that you had built a regen and we both did a double-take. Bill from Soldersmoke building a regen - and enjoying the experience? I was frantically pinching myself, as it just didn't seem likely, given your past bad karma with them but there it was - a lovely old set with that great brushed aluminum finish with the swirls on the front panel - and being worked on by Bill N2CQR. Wonderful!  I have been meaning to either e-mail you, or comment, perhaps below the post in which you featured the letter from Todd VE7BPO. I discovered recently that although we think of regens as being an established, and now stagnant technology, there are still people doing cutting edge research on them.  Some of the discussion was in the Yahoo regenrx Group, and much of the research is being done by a fellow from NJ with the username vladn. Concerning the phenomenon that we notice with our regens that, as we get close to the threshold of oscillation, the bandwidth narrows, and then as we advance into oscillation (as we do to receive SSB and CW), the bandwidth broadens out somewhat, I am going to quote verbatim a comment that was left on my blog by user qrp.gaijin,

This phenomenon has been deeply analyzed and explained (by user “vladn”) here:http://theradioboard.com/rb/viewtopic.php?f=1&t=4680&start=0 . It is, in fact, possible to completely eliminate this phenomenon; bandwidth can be controlled independently of oscillation amplitude (to choose a desired amount of selectivity), and oscillation amplitude can be controlled independently of bandwidth (to control how easy it is for the regen to lock on to the incoming signal: we want a low oscillation amplitude and easy locking for synchronous AM reception, whereas we want a high oscillation amplitude and no locking behavior when listening to SSB). Eliminating this phenomenon, i.e., separating control of bandwidth and oscillation amplitude, can be done by using an explicit amplitude limiter (i.e. a separate transistor/tube stage as part of the oscillator’s explicit amplitude stabilization control loop) that exhibits scale-independent gain compression. In other words, regardless of the oscillation amplitude, if the oscillator’s gain compression (amplitude limiting) behavior is scale-independent, then the final result of the repeated selective amplification (that defines the final regenerated Q and bandwidth) will be the same, regardless of the oscillation amplitude. See this video (by vladn) for a demonstration of independent control of oscillation amplitude and bandwidth: http://www.youtube.com/watch?v=UyqD99WGlss .

The fellow in NJ whose username is vladn has built a regen to test the above theory, and it works! You can see it in the video that is linked in the above quote. vladn has done other equally cutting edge research into regens, but I wanted to let you know that these little receivers are still being developed and improved by a few intrepid experimenters. Howard Armstrong would be so proud!

Best of luck building your regen Steve. With Bill Meara now a regen fan, the radio Gods are on your side!

73,

Dave
AA7EE

****************

Hi Bill and Dave,

The Soldersmoke blog post about the Sproutie super-regen radio by Dave got my soldering iron warm without even turning it on!  That National N Velvet Vernier dial really got my homebrew and radio nostalgia juices flowing with that beautiful nickel plating and the big shiny Bakelite knob.  Plus the use of modern semiconductors along with an Octal socket for the plug-in coils was almost too much to bare.

I immediately bought the National dial and the two variable caps on eBay and from the link Dave suggested in his post for the dial.  That custom chassis company, while in Nova Scotia, is quite close to me here in Maine, and I just might have to visit them to talk about the details of my proposed chassis. 

The obvious next step is a real PCB, but Dave's beautiful technique using the ME squares and pads is hard to argue with.  Those solder-friendly squares and pads are local to me too from good ol' Rex Harper.

Bill, many thanks for your post and link. Dave, thanks for the great design and implementation, as well as the amazing details and photos on your blog.  I think I see a HB super regen project in my immediate future. The parts are piling up!  Gary sold out of the N dials almost immediately.

73

Steve Silverman  KB3SII ... .. ..

**************

I'm really glad that Steve wrote in because his e-mail reminded me that I need to thank him again for the multiband dipole that he sent me a couple of years ago.  For a number of reasons I couldn't really use it in its original configuration, but the wire has been used in almost all my recent antenna projects, including the magnificent Moxon.  The black insulation was just what I needed for that essential stealth effect.  Thanks Steve. 

  

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

Some Inspiration on Receiver Building

As a result of all the recent toob talk with Pete Juliano I've been going to work with old copies of Electric Radio in my backpack.  Yesterday, somewhere in the tunnel under the Potomac River, I read these inspiring words from master receiver builder Bob Dennison, W2HBE (SK): 

"Part of the fun in the radio building hobby is tearing up a set after a short period of use so its parts can be used again in a bigger and better set. Another order is sent to Allied Radio for an audio transformer, an RF choke, a vernier dial and some of those exquisitely beautiful Hammarlund variable condensers.  Oh what a joy it is! You just haven't lived until you've built a whole series of progressively more exotic receivers.  Give it a try!"  (ER, March 1993) 

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

Regen Madness

Dave, AA7EE, has a really nice blog article about his experiences with regen receivers.  He writes about a regen kit he built as a kid (pictured above) and goes on to describe in beautiful detail a regen he built recently using a combination of old tech and new tech:
http://aa7ee.wordpress.com/2014/08/21/the-sproutie-a-general-coverage-regen-receiver-with-plug-in-coils/

I agree with Dave when he notes that regens are unfairly thought of as mere novelties. My old "King's Speech" regen (below) is a very useful shortwave listening  receiver and could easily be used for 40 meter CW contacts.  It is even stable enough for SSB.   

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

Seized up Variable Capacitor -- Any ideas?

Perhaps in retaliation for all the bad things I've said about regens over the years, the main tuning cap in the old regen I've been working on suddenly went from completely loose to totally stiff.  I can turn it, but it is too tight for the old vernier drive in the regen.  I have replaced it with another cap, but this part was kind of the star of the show, situated as it was several inches above the chassis, connected to the tuning control by a long shaft.   I've tried squirting WD-40 in there -- no joy.  I can't even figure out how to open up the part of the cap where the ball bearings should be. It is an OLD Eddystone from England.   Any ideas? 

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

Strange Echo on China Radio International

Last night I was doing some shortwave listening on my new (OLD!) regen.   As always, China Radio International was booming in on multiple frequencies. But as I tuned them in, I noted something strange:  a very distinct echo on the signal (you can hear it in the video above).  Very strange.  Kind of like the Long Delayed Echos we've all heard about.  I started thinking of explanations.  Might this be some weird regen reverb effect?   (You see -- I'm still wary of these regens!)  But no, I checked -- the echo was there when I listened with my superhet HQ-100.  Could it be that this was some strange multipath effect, perhaps involving multiple powerful transmitters in different locations?   I was listening to the 0100-0200 UTC (20 Aug 2014) CRI English language service. (The echo continued when they switched to Chinese at 0200)  I think the frequency was 9580 kHz.   An SWL website says the transmitter was a relay station in Quivican, Cuba.

What do you guys think?  These fellows might have an explanation: 
http://swling.com/blog/2014/07/china-radio-international-warbling-on-daves-home-brew-receiver/

I really like shortwave listening with this old homebrew 1930s radio.  There are still a lot of interesting signals out there.  Recently heard:  Voice of Vietnam,  Radio Turkey, Radio Romania, WWV, WWVH, CHU, W1AW,  transatlantic aircraft,  Radio Australia, Radio New Zealand... and the mysterious numbers. 

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

Happy Birthday Philo Farnsworth!

Thanks to Bob Crane (and Garrison Keillor):  

It's the birthday of Philo Taylor Farnsworth, the inventor of the television, born in a log cabin in Beaver, Utah, in 1906. He conceived of the basic elements necessary to transmit a visual image while he was still in high school; later, at Brigham Young University, he began his research in earnest. He co-founded Crocker Research Laboratories in San Francisco when he was just 20 years old, and the following year, in 1927, he transmitted his first image: a straight line. Investors wanted to know when they would see financial returns, so at his first demonstration for the press in 1928, he transmitted the image of a dollar sign. This earned him the first of about 165 patents.
Farnsworth appeared only once on his invention: He was the mystery guest "Dr. X" on the game show I've Got a Secret in July 1957.
.......

I liked Paul Schatzkin's book on Philo:  "The Boy who Invented Television": Here you can read chapter one for free: 
http://soldersmoke.blogspot.com/2008/08/philo-t-farsnworth-radio-hero.html

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

Alan Wolke Looks at Diode Ring Mixers

Bill,   I remember in your Soldersmoke book that you had difficulty for a long time trying to understand how a mixer created the sum and difference frequencies, and how this was accomplished in a diode ring mixer.  I know that you've got it all sorted out now, but I thought this was a good topic for a video anyway.  

Here's my video on the subject:

https://www.youtube.com/watch?v=junuEwmQVQ8

73,

Alan

Alan:  Thanks.  Great stuff. Yea, I've been looking at the innards of mixers for a long time. In my book, I try to explain how I have come to understand the physics of the mixing action -- how the use of a non-linear element causes two signals to "multiply" and how this "multiplication" results in sum and difference frequencies.  I tried to go beyond the trig functions because for me the trig didn't really explain anything. 

In the book I was looking at the classic two diode mixer (beloved of Doug DeMaw!).  A few years later, on the blog, I was looking at the action of the diode ring.  I concluded that there is a big difference between how the diode ring works and how the two diode mixer works.    RSGB provided a great diagram: 

http://soldersmoke.blogspot.com/2009/04/are-diode-ring-mixers-fundamentally.html

73   Bill 

-----

I guess one way of describing the difference between a two diode mixer and a diode ring would be to say that the more simple mixer multiplies the signal by 0 and 1 (if it is operating in "switching mode), while the diode ring multiplies by 1 and -1.   

 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 #164 Ancient Tribal Knowledge: Tube and Tube-like Radios

SolderSmoke Podcast #164 is available:

August 16, 2014

http://soldersmoke.com/soldersmoke164.mp3

ANCIENT TRIBAL KNOWLEDGE -- TUBE AND TUBE-LIKE RADIOS

Workbench Updates: 
-- Pete's Arduino Keyer Project
-- Bill Builds (and LIKES!)  a REGENERATIVE RECEIVER
-- The Joys of Regen Shortwave Listening
-- Grayson Evan's Tube (Thermatron) Book
-- Book review:  "The Joy of X"  (It's about math).
-- Shameless Commerce:   A Plug for Bill's Book
-- Pete discusses tube projects
-- Making your own enclosures from Home Depot flashing
-- Amplitude Modulation
-- Compactrons, Nuvistors and other unusual tubes
-- BANDSWEEP:   Radio Havana on Bill's new regen 


Bill's Mate for the Mighty Midget Receiver
3 6U8 Tubes on a Benton Harbor Lunch Box Chassis


Nuvistor 2 meter down converter


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

Voice of Vietnam on Old (New!) Regen Receiver

I'm having a lot of fun shortwave listening with the reborn British regen.  This is the Voice of Vietnam. 

I rebuilt the regen using the old Eddystone variable capacitors, the original coil form, the original wooden chassis (now covered with copper flashing) and the original front panel and knobs.  But the old triode was replaced by an  MPF-102 JFET.  And the AF amp tube was replaced by an LM386. Something old, something new... The circuit is the old Armstrong circuit, with a tickler coil and throttle cap.  Thanks to Charles Kitchin for all the regen wisdom in his Nov/Dec 1998 QEX article (available on-line). 

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