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Sunday, August 31, 2014

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: . 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: .

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!




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.

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. 


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Thursday, August 28, 2014

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) 

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Wednesday, August 27, 2014

VE7BPO on the Trivialization of Regenerative Receivers

Todd Gale, VE7BPO, is a true HOMEBREW HERO.  His QRP POPS website has been a source of inspiration and information for many years.    Todd wrote in yesterday on the trivialization of regens and what we should do about it.   Thanks Todd! 

Dear Bill:

With due respect, I challenge the statement that many feel regenerative receivers are trivial.  I submit that most of us know that regens offer good sensitivity + selectivity despite their few parts, however, we ourselves, may trivialize the regen by our lack of literature reviews, experiments, imagination and attempts to improve its downfalls.

Where are the bench experiments and inspired discussion that address issues like designing circuitry to reduce overload and blocking while still maintaining high sensitivity when needed,  hum +  noise reduction, AF filtration, or ways to reduce RF pollution into the RF lab environment?  

Much work on regens and of course, its amazing sister, the super-regen dots the literature. People did make many experiments to explore topics like vario-couplers, litz wire coils with low applied power regen detectors, sensitivity analysis, noise analysis and frequency domain calculations.  
We now tend to see or present ├╝ber basic regenerative receivers complete with LM386.  Yet, still we authors somehow feel people might not respect the regen? Really?

Another factor: as my regen grows in complexity, shouldn’t I just make a zero IF radio (now just as simple with a dongle or two I/Q mixers going into sound card), or perhaps make a simple superhet with some computer crystals for the IF filter?

Regenerative receivers remain cool.  Perhaps putting both hands on the controls plus the antenna coupling are just part of the regen experience and like a standard versus automatic transmission, offers more visceral listener engagement?  

No doubt, nostalgia and love for simplicity color the regen experience.  Now is the time to make a regen — If you listen carefully — inside many big cities the crashing sound you hear is yet another SW tower coming down.  

Hats off to you Bill and also to Dave, AA7EE for his stellar blog presentation.

Todd, VE7BPO

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Tuesday, August 26, 2014

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:

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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Friday, August 22, 2014

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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Wednesday, August 20, 2014

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:

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. 

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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:

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Monday, August 18, 2014

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:


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: 

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.   

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Saturday, August 16, 2014

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

SolderSmoke Podcast #164 is available:

August 16, 2014


Workbench Updates: 
-- Pete's Arduino Keyer Project
-- 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

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Tuesday, August 12, 2014

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). 

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Some Progress on the Old Regen

That's Radio Havana Cuba.

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Saturday, August 9, 2014

Jim, WB5UDE's Knack Story

Hi Bill! ...

Of all the Amateur Radio related podcasts I've sampled, SolderSmoke has
been my favorite.  The reason is because of the passion you (and Mike,
too, in the beginning) bring to us each and every episode.  I've been
passionate about radio since I was 10 years old, and electronics in
general since I was about 8.  Many of the other podcasts seem to lack
this quality, or worse, try to have a "how to do things in Amateur Radio
the right way" focus.  I suppose their thinking is that hams listen to
podcasts to learn, so they assume their job is to tell someone how to
get started doing this or that.  However, the result often comes off
being preachy-- that there is a Right Way to do things, and that it's
important to do things that way, so they'll work out best.  That's not
what Amateur Radio is about!  Amateur Radio is about doing something
because you're passionate about it.  Even where your own passions are
concerned (e.g. individual analog components, no chips!) you acknowledge
that the other approaches are equally valid, and that we should all
do what we enjoy.  You're not shy about branching off into your other
technological passions, about space, RC aircraft, etc., which as you
rightly observe, so many of us have in common.

We share a passion for learning and understanding about radio/electronics.
Where we differ is in the depth of understanding we crave.  Actually,
I have experienced enough of that desire for total understanding to know
exactly what you're talking about, but I'm usually content without it.
I realized back when I was a teenager that some things would click for me
right away, and some others, I'd always struggle with.  I made peace with
that very early.  Still, I have wondered more than I could find ultimately
adequate explanations for about things like, OK...exactly what ARE these
radio waves?  More often, though, I am content to gain a sufficient depth
of understanding that I feel comfortable knowing how I might achieve a
particular thing.  I have great sympathy for your struggle with "holes" in
transistor theory.  That actually clicked for me, but not immediately--I
had to chew on it just a bit, but then it did gel.  If that "?" floating
over my head had refused to disappear, I might have found that a little
frustrating.  But to me, the really frustrating thing is that books so
often begin by talking about electrons and holes and depletion zones and
so forth.  I have found that a much simpler explanation is sufficient
for my tastes--I'm content to understand that there are N-doped and
P-doped sections, and that this allows the silicon to control current
in a certain way.  Knowing how we arrange the electronics around a
transistor to get it to behave in its own useful way in a circuit is
really all I've ever cared to know.  And furthermore!... I'd rather
have the whole presentation be top-down...I'd rather start with what a
transmitter and receiver are, and what their stages are, and what kind of
circuits go into those stages, then eventually, down to what components
make up those circuits.  It's all a natural progression, for me, of, "OK,
I understand that--now, how exactly does that part work?  Give me more
details, please."  The whole thing of just learn all these fundamentals,
and we promise we'll eventually tie them together into something useful
doesn't work well for me as a way to learn.  Worse than that, it doesn't
thrill me to the core the way gaining a gradually deeper and deeper
understanding does, as I drill down into more and more detail about
things I've caught an interest in, and remain content with a shallower,
surface knowledge of things I just want to know well enough to use,
when I need them.  So, I don't have the same burning desire to get down
to the bottom foundation in first principles all around that you do,
but I do love to learn, and understand.

I got my start in electronics when I was eight years old, and read a
book my parents had bought me about electricity.  I suddenly realized
that things like flashlights and motors didn't have to be a strange
mystery, but were things I could understand, and even try for myself.
I began reading everything I could find at school about electricity.
Meanwhile, over the next couple of years, I began appreciating music.
Reproducing music was something very special that electronics could do.
Even more special, radio electronics could bring you this music from
far away.  That whole combination, bringing communication from far away,
including things I found enjoyable, and doing it with this wonderful
magic of electricity, which it was possible to actually understand, was
(and still is to this day) quite thrilling.

When I was ten years old, I realized that, lo and behold, it would
actually be feasible for the amount of money my parents would be able
to spend for a Christmas present, to buy a pair of toy walkie- talkies.
I set a new level of obnoxiousness leaving the catalog open to the
page with the walkie-talkies, and finally, just flat out telling them
that's what I wanted.  I then exceeded that level of obnoxiousness when,
I'm ashamed to say, I absolutely chewed them out when they didn't take
the hint.  Instead, I got a tape recorder.  I actually enjoyed that, too,
but continued to campaign for the walkie-talkies, and when I still wanted
them a year later, my parents decided I meant it, and bought them for me.
(My dad knew a thing or two about radio himself, and my mother later
told me that my dad had been concerned that the walkie-talkies would be
fragile, would perform poorly, would chew up batteries like you couldn't
imagine, and would have a very disappointingly limited range.  He was
right about all those things, but it turned out I was right, too--in spite
of all that, I loved those walkie-talkies as much as I'd known I would.)

Meanwhile, I got a 100-in-1 electronics set for my birthday.  My parents
had wanted to find one that was about individual components, but all
they could find was one that was based on projects using a pre-built
audio amplifier, radio receiver, speakers, and battery holders.  Its only
component-based aspect was an apparent afterthought, an AM BCB transmitter
built on a cardboard circuit board.  This was really a bit too "appliancy"
for me--I would rather have been learning how to make components work--but
I still learned a lot from that.  I also bought an AM clock radio for
less than a dollar at a garage sale.  It didn't work very well, but this
was really good, because I learned that I could make it work much better
by wrapping a few turns of wire around its built-in loop antenna, and
attach that to various antennas I got to experiment with.  Months later,
I found a very nice tube-type AM/FM Zenith table radio at another garage
sale, and bought it for $5.  That radio went home with me strapped to
the back of my bicycle, then went on the bookshelf on the headboard of
my bed.  I learned to work its knobs backwards, reaching behind my head.
I listened to AM radio stations from all over the US until all hours of
the night, and my addiction to radio grew even deeper roots.

Then, when I was 13, I found a Zenith Transoceanic portable at a
garage sale, for $15.  I raced my bicycle home as fast as I could.
(This radio was a little too big for the bicycle.)  I got my mother to
drive me back there (urging her to hurry!  before someone else bought it),
and brought that one home....  then spent that whole evening driving my
parents nuts by running into the room where they were every few minutes,
excitedly exclaiming something like, "and NOW I'm getting a station from
GERMANY!" and then running back to see what I could get next.  Of course,
I had even more fun with it after I put a decent outdoor antenna up.

When I was 16, I finally met an Amateur Radio operator.  I'd read an
ARRL book about becoming a ham, and building one's own station, but the
books were a little expensive, and I wasn't sure how to go about it all.
Pat Barge, WB5OEB, about one year older than me, had earned his license
about a year before, and was eager to pass along the favor of showing
the ropes.  I got to listen as he operated his station, and he told
me which books would give me the specific knowledge I'd need to pass
the tests.  I was 17 when I got my first license.

While I was learning what I'd need to get my first license, I got my
next great receiver--this time, an RAL-7 regenerative receiver.  You and
I very much see regenerative receivers differently, but then, I had
the pleasure of learning on the best regenerative receiver ever made.
Back in those early days, I'd sometimes hear the opinion that the RAL-7
was not merely the best regenerative receiver ever, but the best receiver
ever, period.  I think all those old-timers have died off, though.

I've enjoyed building a bit over the years, too.  I haven't found nearly
as much time for it in my adult years, so I think to this day, about
half of my building was done as a teenager.  I haven't done anything
impressive, but I have made contacts using things I've built myself, and
what a thrill that is!  I've built more than a dozen projects (but fewer
than two dozen).  The most fun I've had was several years ago, following
the advice of a post to the Glowbugs list, I began experimenting with
crystal radios, then slowly began to ramp the circuits up, adding tube
amplifiers, tuned circuits, etc.  My favorite successful project was
a SWL converter to feed a car radio.  I built a doubly balanced diode
ring mixer and a crystal oscillator.  I used a 3-gang air variable
as the foundation for a 3-stage front end filter.  I had an 8.x MHz
crystal that put signals from (depending on where I tuned that 3-gang
air variable) either the 49 m or 31 m shortwave broadcast bands in the
tunable IF provided by the AM car radio, which fed a nice 3-way speaker
from a stereo, for the most beautiful sounding SWL listening of my life.
Like all my projects at that phase, it never left the breadboard stage,
but it stayed on the breadboard for a long time, while I paused in my
building to enjoy listening for a while.

I serve as one of the net control stations for a local two meter FM net
that meets weekly to discuss technical topics.  We got our start back
before most folks had Internet access, and served a very useful role as
the place where hams who had a problem to solve or wanted to ask how to
get started in a new phase of Amateur Radio could come and get answers to
their questions and ideas about how to do things.  In these days where
it's easier to Google for answers, we've morphed into more of a general
discussion session among a small, dedicated group, but it's still a lot
of fun.  It gives me a chance to do what I enjoy the most consistently
in Amateur Radio, which is to understand, talk about and explain things.
In fact, that's often all I find time for.  Other than the weekly net,
I sometimes go a long time without actually getting on the air.

When I do get on the air on HF, it's almost always CW.  I've always
struggled with Morse, which has never come easy to me, but I enjoy it.
Every time I return to HF after having been away for a while, I think,
"This time, I'm going to do some SSB" but every time I actually sit down,
I think, "But tonight, I'm going to do CW."  I can't explain why I like
it better, but it just seems to me to be a particularly special part of
the magic of radio.

Before closing, I'd like to finish by responding to something you
mentioned in episode 162.  You told about a member of the audience at a
talk you gave, who was asking about how much time it had taken you to
build a particular radio, seeming to suggest there was a price to pay
by investing all that time.  I love to explain to people that there is
a whole different economics to Amateur Radio.  In my professional life
in IT, I'm always promoting the idea that we should deploy and install
systems so that we will expect them to work trouble free throughout
their anticipated lifespan.  People balk at the expense of doing it
that way, but it's my job to remind them that the cost of having it
fail, in lost productivity, is far greater than the expense of doing
it right in the first place, not to mention the fact that coming along
later and remediating an inadequate deployment usually costs more than
it cost to do it wrong the first time, let alone the incremental cost of
doing it right.  Similar ideas prevail with radio.  We see professional
radio installations where many thousands of dollars are spent doing
things that we hams rarely even consider.  For many of us [raises hand]
we must do Amateur Radio out of a meager budget for entertainment,
or not at all.  But even more importantly, if we enjoy doing these
things, then the time spent laboring at our projects--transmitters,
receivers, antennas, etc.--is not a liability at all; it is an asset!
If assembling a kit, or planning and building some unique project, or
putting up a different antenna every six months, is something we truly
enjoy--even LOVE doing--then that time spent is no hardship at all.

Thanks, Bill, for the time and effort you put into providing us with
an episode of SolderSmoke from time to time.  All my life, I'd wished
for TV and radio shows about Amateur Radio, and now, they're finally at
my fingertips.  Your gift to the hobby is deeply appreciated.


Tuesday, August 5, 2014

Moonlight Moxon

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Saturday, August 2, 2014

Video: Regenerative Receiver Project!!!

Pete Juliano and Grayson Evans are luring me back into the world of tubes and (gasp!) regen receivers.  

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