Single Transistor Regen Has QSO Potential (Video)

In my previous blog post I'd expressed skepticism about using a single transistor regen on the air.  But over the years I've learned to give new receivers a chance.  They usually don't work perfectly on the first try.  You have to work with them.  It is almost as if you have to peak and tweak a lot in order to get them to properly inhale signals from the ether.  

That has been the case with this little receiver.  I found some silly mistakes in my construction.  And I decided to try some more sensitive headphones.  I ditched the 1000 to 8 ohm AF transformer.  And I added a very small variable cap for fine tuning.  

The results are amazing. See video above. It performs as well as most of the direct conversion receivers I've built. It is remarkably stable.  

I do think I could make contacts with this receiver.   I might eventually go the full ET-1 route and try to do it with a single switched FET, but I think my next step will be to built a single transistor crystal controlled transmitter on the same piece of wood, and try to make some contacts with a two-transistor rig. 

Clockwork CW: The Path to Minimalist QRSS?

Well, maybe not using that one. But something like it. The idea -- mentioned recently on the podcast -- is to use a mechanical clock mechanism to generate the CW for a QRSS beacon. This would allow us to get the transistor count for our beacon down to one. For some odd reason, some of us find this appealing, especially when you consider that the transistor count on the receive side is in the tens or hundreds of millions. One is the magic number. You can see how this project brings together two of the biggest littlest recent trends in the QRP radio: QRSS and minimalist radio.
It's kind of scary when you Google something and are referred back to your own blog. That's what happened to me on this subject. Back on May 28, 2008, this was posted (by me!) as a comment to one of the beacon-related posts:

Hello Bill and Others:
A few years ago, a buddy had made a neat keying operation made by taking a
one RPM clock motor and had it rotate a printed circuit board disk that had
the callsign etched on it several times sequentially. Clock motors are
made to run continuously for years, and it stood up with just an
occaisional cleaning of the wiper arm with spray cleaner.
All the best to all!
73 de Lee Smith VE4ANC

This message from Lee was a response to a January 1999 question from me. So we are sort of re-inventing the wheel here.

Of course, there are some QRSS beacon circuits out there with VERY low transistor counts. Hans Summers has one on his site that used a bi-stable multivibrator to generate a pattern for QRSS. That would yield a total transistor count of 2 or 3. But we are going for one single transistor. And I kind think we should look for something that will allow for the transmission of callsigns.

Here's an e-mail exchange from the Knights of QRSS mailing list that may generate some ideas:

Re: [Knightsqrss] Junkbox + soldersmoke = pattern generator

Saturday, March 7, 2009 10:43 AM

From:"Paolo Saia"

To:"n2cqr"

Very nice idea Bill. After tiny solar mepts this could been our next QRPP/ET challenge .
73 de Paolo IZ1KXQ
--------- Initial Header -----------

From : knightsqrss-bounces@cnts.be
To : knightsqrss@cnts.be,"Soeren Straarup" xride@x12.dk
Date : Fri, 6 Mar 2009 21:48:55 -0800 (PST)
Subject : Re: [Knightsqrss] Junkbox + soldersmoke = pattern generator
It would be fun if the clock were a "wind up" type. And for extra credit: Power the transmitter with the energy from the same spring mechanism (or other wind-up device) that powers the clock!
ET PHONE HOME!
--- On Fri, 3/6/09, Soeren Straarup <xride@x12.dk> wrote:

From: Soeren Straarup <xride@x12.dk>
Subject: [Knightsqrss] Junkbox + soldersmoke = pattern generator
To: knightsqrss@cnts.be
Date: Friday, March 6, 2009, 3:30 PM
Hi list,
Hans Summers has made an astable multivibrator as pattern
generator.
Bill Meara has thought about making a analog clock.
Alan Yates loves my idea of an exercise bike pattern
generator.
Though i'm open for suggestions. No pics, pc or
any other programmable
devices.

Rules of design:
1) KISS
2) Should be in most junk boxes
3) Pattern should be easily changed (diversity, more
homebrewers)
4) KISS
This is for a simple Pixie2 TX modified to be a QRSs TX.
Stability? SSShhh.
Vy 73 de OZ2DAK
Soeren Straarup | aka OZ2DAK aka Xride

More on the ET-2 : Better Pictures and More Circuit Description. Some Thoughts on Simplicity

 

So yesterday I made my first contact using my ET-2 rig.   Last night I got an e-mail from Gary, the fellow at the other end of that contact: 

Evening Bill, N2CQR….Yes I did learn about you from the spot on the DX Summit cluster. I tuned to the freq to see if I could even hear your 80 mW and you were a good real 569 when calling CQ.  You built up to a real 589 on the later transmissions. I did not have either of the two pre-amp positions on in the ICOM 756 Pro II. There was not any QRM on the freq either. Your spot indicating the 80 mW is what really got my attention.

My antenna is a 2 element yagi at about 115 ft and it really works great for me.

Thanks for the picture of the great little transmitter. Glad to be your first DX QSO with it. Hi Hi  Maybe again soon.  My pleasure to work you.

73, Gary, K4MQG

Fort Mill, SC

Farhan commented on yesterday's post, saying that it was hard to tell (from my pictures) where he rig started and ended.  He was right.  So this morning I have tried to clean up my bench a bit -- I hope these pictures are better.  

Above you see the whole rig.  The transmitter board is right next to the key that Farhan gave me.  You can see the 7040 crystal.  A C-Clamp holds to the bench the piece of scrap plywood that serves as the base for this rig.  Next to the C-Clamp you see the TR switch -- the just switches the antenna -- both transmitter and receiver are powered at all times.  I can hear the transmit signal in the headphones and this serves as my sidetone. 

Here is a close-up of the transmitter with the schematic below: 

 

The transmitter is VERY simple.  Nine parts, including the low-pass filter.  You can barely see the J310 FET to the right of the crystal. 

Here is the receiver:

I really like N0WVA's regen.  The green diode in the source circuit is the key.  This one does not squeal when you go into excessive regeneration (when you think about it, regens should NOT squeal at audio frequencies -- but most do).  Also, the green diode dims a bit when you are at the right amount of regeneration.  In the picture you can look down the tube of the variometer that Pericles HI8P gave me many years ago.  The big variable cap is from the junk box -- I think it may be from a Johnson Viking transmitter.  Note the long shaft with the insulating connector -- this is to reduce the hand capacity effect.  On the right you see a smaller cap with just one vane -- this is my fine tuning control --- with the smaller cap at mid range, I would just set the big capacitor to put the receiver at 7040 -- with the smaller cap I could tune +/- 12 kc.  I also used an insulating shaft on the smaller cap -- the connector for this one is from an old 1930s era regen that I picked up at the Kempton Part rally in London.

Instead of the audio transformer and Radio Shack headphones, I just used some old DLR-1 WWII Headphones.   They are very sensitive and work well. 

Lots of soul in this new machine:  The variometer from Pericles.   The WWII headphones.  The 1930s era shaft connector.  The circuit idea from the Autumn 2001 SPRAT.  Farhan's key. 

I recently read on Hack-a-Day of a new FPGA chip that has on it 35 BILLION transistors. I'm sure that thing can produce some fascinating results, but can anyone really understand it, or feel that they really BUILT something that has that kind of chip at its center?   On the other hand, I did rely on a lot of modern digi technology in this project:  The Reverse Beacon Network reported back that my unanswered CQs were in fact getting out (one as far as Kansas to K9PA).  And in the end I had to ask -- via the DX Summit Spotting cluster -- for someone to listen for me.   So I can't go full Luddite here.  And I wouldn't want to have to use a rig this simple every day.  No way.  It is just too hard to use. But there is a beauty and a challenge in simplicity.  There is some virtue in using just two transistors instead of 35 billion. 

Thanks to N0WVA, W2UW,  VU2ESE, HI8P, K4MQG, The G-QRP club and their inspirational journal SPRAT, the RBN and the DX Summit. 

Messaging ET (METI), and Silicon-based Life Forms

My fellow beacon fans will like this one. The ultimate (REALLY ultimate) beacon! http://www.newscientist.com/article/dn21236-lets-build-a-beacon-to-tell-aliens-who-we-were.html?page=1

And then there is this article about silicon-based life forms. (At first I thought they were talking about us!) http://www.universetoday.com/91449/why-silicon-based-aliens-would-rather-eat-our-cities-than-us-thoughts-on-non-carbon-astrobiology/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

EMRFD Joy of Oscillation (Part 1)

Guys:

I have been catching up on the last few SolderSmoke podcasts after
that little QSO Today diversion.  I wonder how many others did the
same thing?  I have really enjoyed these recent 'casts.  Lots of
fantastic HB content.  Funniest moment was when Bill described his
post-project workshop as looking like the aftermath from an electronic
barfight.

I took a new ham up on a SOTA activation last year.  Then about a
month ago, he said that he wanted to do HF HB.  He said he had been
googling and found so much that he didn't know where to start.  I told
him that I'd be interesting in doing a beginner HF HB project with
him.

I could have pointed him to LBS, et al.  I could have pointed him to
the Michigan Mighty Mite.  I did neither.  I pointed him to:http://web.cecs.pdx.edu/~campbell/EMRFD1dot34.pdf  Note the name of
the document.  I pointed him also to:http://www.arrl.org/files/file/Product%20Notes/chapter_1.pdf 
(Did you guys know that chapter was online and free?)  We scaled to 20m and
kitted parts for this.  And parts for a 4th transistor PA for serious
QRO.  :-)

Two others joined us building for 40m.  Check out the attached photos
of the first 3.  The joy of oscillation was experienced by all.

After testing each oscillator, and borrowing from an article KK7B ran
in CQ VHF, I told each that he had to ID every 10 minutes.  Even
though nobody was going to hear these signals a few hundred yards
away.  (But it sounds loud on a shortwave portable a few inches away!)
 I even wrote out the dots and dashes for a couple of them.

Next stop:  to have everyone find a curbside TV discard, rip out some
parts, and get on 5 meters!  Haven't we gotten it back now, after the
transition to digital TV?   :-)

OK, maybe the next stop is to add some gain stages and experience the
joy of communication.  The joy of QSO-ification?  The joy of
EM-radiation?  :-)

Best regards,

Drew
kb9fko

2 Attachments

SolderSmoke Podcast #104

http://www.soldersmoke.com

1 April 2009
Rome Marathon
Billy climbs Vesuvius!
Fixin' up old Toshiba laptop
Solar Power from Donuts and Tea!
Eldon's MEPT ET Phone home machine
More Catalan minimalism: The MOSquito
Book:  Thunderstruck! Marconi history
SPECIAL ECHOLINK QSO WITH NIGEL, M0NDE
MAILBAG:
Paul M0XPD new homebrewer, Funster 40, Paraset, and SDR
Preston WJ2V on REAL solder vacuum pumps
Ted AA5CK keys MEPT with iduino
Ken KG6PO on obit of TV pioneer Thomas T. Goldsmith
Art W2HQQ: "Man of High Fidelity" lacks knack
Scott KD5NJR on Sputnik 4, NASA comms
Alan W2AEW Don't smother MEPT oscillators! Books
Steve GOFUW Old Book recommendation. Building WARC rig
Jacki (XYL of KL7R) says hello from volcanic Alaska
Jeff KO7M  Why FSK on QRSS?
Jim AL7RV Sends WSPR care package.  (Thanks!)