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.   

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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? 

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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