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Thursday, September 21, 2023

Marb Builds a Replica of Michael Faraday's Motor

Really cool, at a couple of levels.  First, well, Faraday's motor.  Cool enough right there. But also very cool is the workmanship.  Marb (in Germany) clearly knows how to work the metal.  Lots of tapping and dieing.  I also liked the way (with a flame!) that he stripped the enamel off the wire.  The fancy feet on the board and the varnishing were really nice touches. 

Thanks to HackADay for alerting me to this.  And thanks Marb! 

Wednesday, September 20, 2023

The Art of Electronics #5 Paul Horowitz on SETI (and lots of other radio stuff)

In 2016 Paul Horowitz  talked about SETI at Google. Fascinating stuff.  Paul did an especially good job of weaving in a lot of radio/electronic and computer info.  

-- I was pleased to learn that one of the early radio astronomy antennas used plywood covered with copper.  I hope it was copper tape! 

-- I didn't know that the Fast Fourier Transform was something developed in the 1960s. 

-- Parkes Telescope!  Yea! 

-- Paul's "chirping" of receivers to screen out targets that are NOT doppler shifting (i.e. terrestrial signals). 

-- Paul tells the group that "amateur" does not mean unprofessional -- it means that the person is doing it for the love of doing it.  Amen. 

-- SETI at Home. 

-- Tube op-amps!  (was that two 12AX7s?)  

--  A variometer!  Wow!  I have two here -- one in the ET-2 regen receiver  (a gift from Pericles HI8P), and another that I homebrewed using a 35mm film can.  

Great stuff from Paul. 

Tuesday, September 19, 2023

"The Art of Electronics" #4 Boom! Putting Diodes Across Relay Coils

I think this is a good example of the practicality, and the style (BOOM!) of The Art of Electronics.  This shows very nicely how failing to put a diode across a relay coil can get you into a lot of trouble.  Boom, indeed. 

Sunday, September 17, 2023

"The Art of Electronics" Post #2 Interview with Lady Ada (Video)

I posted this video back in 2015,  but it is so good that it is worth watching again.  This is especially true now that I have the second edition of  The Art of Electronics  in hand, and in light of the fact that we recently had our own experiences trying to teach analog electronics to students. 

Paul Horowitz is a real inspiration.  He is still W1HFA, and QRZ.com has him living in Cambridge, Mass.  So many great tech collaborations came out of that fair city:  Car Talk and KLH, just to name two.  And of course, Horowitz and Hill. 

It was wonderful to hear Paul describe the origins and the evolution of The Art of Electronics.  His description of the Electronics 123 course at Harvard was really inspiring.   They were wise to limit the participation to 10 students (it seems that they eventually went to 2 sections of 10 students each).  I think Dean KK4DAS and I came to the conclusion that it is better to have a small group of truly interested students than to have a large group of marginally interested students. (At the high school, we started with 70.  That was far too many.)  And it may be better to teach this stuff at the college level (high schoolers may be a bit too young).  I want to get the third edition, and the book Learning the Art of Electronics.  

Paul showed pictures of the class (near the end of the video).  Classroom seating was seminar-like, with no pompous professor at a podium.  The labs showed Rigol digital 'scopes in use.  

And wow, the watch that Paul gave to Lady Ada is very cool. 

It is all quite inspirational.  Three cheers for Horowitz and Hill, and for Lady Ada.  

More on "The Art of Electronics" to come. 

Saturday, September 16, 2023

"The Art of Electronics" by Horowitz and Hill (First in a Series of Blog Posts on this Great Book)

Paul Horowitz

Oh man, this book is so good.  You really just need to buy it now.  I put it in the Amazon link to the right.

OVER HERE >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

The Imsai guy reminded me of this book, and pointed out that earlier editions are more reasonably priced, so I got the second edition (looks like 1980, reprinted many times through 1988).   Dean KK4DAS got one too (I think he also got the second edition).   

Lest there be any doubt that this book is for us, first let me point to the pictures of Paul Horowitz and Winfield Hill.  https://artofelectronics.net/about/

Winfield Hill 

Just from the pictures, you can tell that these guys have THE KNACK.  And -- get this -- THEY ARE BOTH PROFESSORS AT HARVARD.  Wow. 

Their web page explains where the book came from: 

Dean KK4DAS and I have already started sharing quotes from the book: 

Referring to other books, H and H  write:  "Much of the favorite pedagogy of beginning textbooks is quite unnecessary, and, in fact, is not used by practicing engineers, while useful circuitry and analysis lies hidden in application notes, engineering journals, and hard-to-get data books." 

"Thus, the treatment of this book reflect our philosophy that electronics, as currently practiced, is basically a simple art, a combination of some basic laws, rules of thumb, and a large bag of tricks. For these reasons we have omitted entirely the usual discussion of solid state physics,  the h-parameter model of transistors, and complicated network theory, and reduced to the bare minimum the mention of load lines and the s-plane.  The treatment is largely non-mathematical, with strong encouragement of circuit brainstorming, with mental (or, at most, back-of-the-envelope) calculation of circuit values and performance." 

Stay tuned.  There is a lot more coming about this wonderful book. 

Friday, September 15, 2023

HB2HB -- A Contact with Denny VU2DGR (video)

At first I didn't realize it was Denny.  On September 11, 2023 at about 2330Z I had walked back into the shack after dinner.  I think DX spots showed an Indian station on 20 meter SSB.  Without realizing who it was, I tuned him in on my Mythbuster rig, heard the other station sign off, and quickly threw in my call.  Denny came back to me right away, and I think both of us then realized that we recognized the call of the other station. Wow, it was Denny, VU2DGR, the Wizard of Kerala!   At the time of the QSO, I didn't have my phone with me; after we spoke, I went to get it,  so the video above captures part of Denny's subsequent contact. (You can also at one point hear Guapo barking.) 

Denny has been running a wonderful station that combines SDR gear with and HDR tube type amplifier and a homebrew Moxon.  

Here is Denny's station. The transceiver is a RadioBerry.  the amplifier and power supply are on the other table.  

Here is the homebrew tube-type amplifier.  This is the part of the station that really puts the HB in HB2HB! That's the power supply on the left and the amplifier itself on the right: 

That amplifier has three 807s in it, with a 6L6GC: 

Here's a video on the RadioBerry transceiver. 

Finally, here is Denny's magnificent homebrew 20 meter Moxon: 

Thanks Denny! 

Thursday, September 14, 2023

Building Nixie Tubes for a Hiroshima Project

Thanks to Bob Scott KD4EBM for alerting me to this wonderful video.  It seems especially timely, given the recent release of the Oppenheimer movie.  

I posted back in 2000 about Dalibor Farny and the Nixie tubes he makes in a castle in the Czech Republic:

In this more recent video (above) Dalibor describes a very cool and very challenging Nixie tube project:  A museum in Hiroshima Japan was presenting an art project designed by a Chilean artist.  The display needed a lot of large, custom-made Nixie tubes, some of which would display Japanese language characters.  So: Museum in Japan, Chilean artist, Nixe maker in the Czech Republic.  There are big geographic challenges before you even get to the technical challenges.

Dalibor does a great job in describing all of the challenges that they faced.  The technical stuff will be especially interesting to SolderSmoke listeners.  His description of the evolution of his Czech workshop fits very well with our "other kinds of workshops" theme. 

The video is really worth watching.  Check it out (above).  The ending is quite moving. 

Thanks again to Bob Scott.   Congratulations to Dalibor, his crew, and to all those involved in this Hiroshima museum project. 

Tuesday, September 12, 2023


With the help of several loyal SolderSmoke listeners, we finally cracked the code and figured out how to put the new Amazon Ads on the blog.  You can see it on the right side of this page. 

Right over here >>>>>>>>>>>>>>>>>>>>>>>>>

You don't have to buy whatever we are advertising.  Just click on the SHOP NOW sign and begin your Amazon shopping there.  In this way SolderSmoke will get a small commission on any purchase you make (within 24 hours of your initial click on the SHOP NOW icon). 

Friday, September 8, 2023

Why Building for 10 Meters is Harder than Building for Lower Frequencies

Recently my trusty CCI EB63A .1kW amplifier has been in rebellion.  On 10 meters, it now often insists on being an oscillator.   It calms down nicely on 20 meters.  But on 10, it has been a rebellious beast.  

Why is this?  Why would an amplifier that is well behaved and stable on 20 meters behave so badly on 10 meters?    

I used LTSpice to explore the problem.  

I looked at two ordinary wires.  I gave them each a value of .003 uH.  Very low.  Then I joined them together in a transformer.  I put a 1 volt signal into the primary and looked (in LTSpice) at how much of a signal appeared in the secondary.  First, the result on 14 MHz.  About 250 mV appears on the secondary. 

Now consider what happens at 28 MHz.  Nothing else in the circuit changes.   Just the frequency.

Here we get about 450 mV.  A lot more.   

Realize that my little EB63A amp has lots of wires in it, most of which are ready to serve as primary or secondaries in circuits like this.  Increasing the frequency makes it more likely that a ginal will jump to someplace that it is not supposed to be.  Output will couple to input and the Barkhausen criteria will be met. The amplifier will become an oscillator.   

Of course, something similar happens with capacitive coupling.  Same story:  the higher the frequency, the harder it is to keep the amplifier stable. 

Don't worry:  Improved shielding is saving the day.  The amplifier is now stable on 10.   More about this in the next podcast... 

Monday, September 4, 2023

SolderSmoke Podcast #248 -- Back from the Summer -- Spurs and Filters, S-meters, 6BA6 mania, Shirtpocket rigs, MAILBAG

The PsssT Kit, coming soon from Mostly DIY RF

SolderSmoke Podcast #248 is available for download: 

Audio: http://soldersmoke.com/soldersmoke248.mp3

Video: (800) SolderSmoke Podcast #238 -- Spurs and Filters, S-meters, 6BA6 mania, Shirt-pocket rigs, Mailbag - YouTube

Travelogue:  Trip to the Dominican Republic 3-9 August.  Thinking about the M0NTV video on mixers...  

Solder Smoke Shack South is almost done.   I am thinking about workbenches, operating tables and antennas.  How high should an electronics workbench be?   Table height?  Or workbench (woodwork) height?  

My son and I went to see "Oppenheimer"  Trinity test scene very cool.  They wanted to see if the gadget would work! 

Is the SolderSmoke blog completely archived on the WayBack Machine?  Please check and let me know.  Thanks. 

Bill's Bench: 

-- I've been working a lot of DX with the homebrew rigs:  Indonesia, Australia, Japan, Hawaii.  Lots of fun.  15 meters has been especially good. But the rigs still need work: 

-- M0NTV's video got me to put TinySA to work.  I found that output from dual banders could be improved.  Spurs and harmonics. Yuck.  I need more TinySA -- ordered the TinySA Ultra. 

-- Allison KB1GMX helped a lot.  EB63A amp was unstable, especially on 10 meters.  Higher frequencies are harder!  Tightened up shielding, negative feedback, and bypassing.  This all helped, but I found that I needed to take the higher frequency LP filters out of the amplifier box.  W3NQN filters are better, with steeper skirts and better 2nd harmonic rejections. NanoVNA proving very useful. https://www.gqrp.com/Datasheet_W3NQN.pdf

-- Also worked on the Bandpass filters for these rigs.  Farhan's comments on skirts of different filter configurations.  Some are "LSB" filters (with steeper skirt at the highest freq) and some are "USB" filters (with the steeper skirt at the lower frequency)  See diagrams on the blog page. So I built USB new filters for 12 meters and for 10 meters. 

-- Danger that my unshielded wooden box rigs might be inviting feedback.  So I shielded the 1510 rig with copper guitar amp tape (conductive adhesive).  Good stuff.  

-- Phase Noise rears its ugly head again.  See blog posts. 



Mostly DIY RF getting ready to release PsssT kits.  Target date:  December 18, 2023 (E Howard Armstrong's birthday).  https://mostlydiyrf.com/

Amazon Search box seems to have died.  I can't get it back.  Can anyone tell me what happened?  (There seems to be "explanations" from Amazon about this, but they are written in a strange language that I cannot follow.)  Something similar happened with the Google Ads on this blog page.  Apparently you can't have ads both on YouTube and blogger.  

But hey, there is Patreon for those who want to support the podcast and blog. 


Pete's Bench

An S-meter for Bill? 

6BA6 Mania! 

QRP SSB with 6BA6

Shirtpocket rig re-build


Walter KA4KXX has a great article about homebrewing in the September 2023 QCWA Journal.  

 Steve KC1QAY -- Has joined the CBLA.  I sent him a 3579 crystal.  He built a MMM and experienced JOO.  And Allison KB1GMX is in his local radio club.  TRGHS. 

Ajay VU2TGG in Pune, India -- launching a high school receiver effort. 

Denny VU2DGR The Wizard of Kerala: https://soldersmoke.blogspot.com/2023/08/the-wizard-of-kerala-india-denny-vu2dgr.html

Joe VK4BYER working with kids a remote Australian community.  FB. 

Todd K7ZF -- Wants to get into homebrewing. Advised him to start small. 

Dean KK4DAS:  Fixing Hallicrafters Worldwide RX. Ciudad Trujillo!  Got question from Mark in the VWS Makers Group:  HOW DOES Michigan Mighty Mite REALLY Work.  See blog. 

Trevor Woods -- Info on Super Islander Mark IV made in Cuba from old CFL bulbs.  FB. 

Bob KD4EBM sent me some great stuff:  Sony SW receiver,  QCX Mini.  Made a CW contact with the QCX.  Felt virtuous -- it is going to the DR.  Thanks Bob. 

Peter KD2OMV:    One of the guys I worked with the ET-2 transceiver.  Great to hear from him. 

Armand WA1UQO   Richmond area radio museum? https://www.youtube.com/watch?v=BSCmljje1p8

Mike WN2A -- Sent me a great care package with lots of toroids.  A lifetime supply!  Thanks Mike!

Nate KA1MUQ got his Doug DeMaw receiver going after 38 years!  FB.  Been there, done that! 

Tony: G4WIF Liked Valveman video about Gerald Wells.  He visited him! https://soldersmoke.blogspot.com/2023/08/valveman-story-of-gerald-wells.html 

Dean KL7MA  Bill talked to him on 15 SSB.  He had worked Wes W7ZOI!  FB! 

Monday, August 28, 2023

But How Does the Michigan Mighty Mite REALLY Work?

Dean KK4DAS and I were talking to Mark, a new homebrewer.  After we sang the praises of the Michigan Mighty Mite,  Mark asked us a good question:  How does it really work? 

I guess the starting point for analysis is the Barkhausen criteria (that Pete N6QW taught us):  essentially you need enough feedback to overcome losses in the circuit, and this feedback has to be in phase with the signal at the input.  The MMM is clearly oscillating, so the question becomes, "How does this very simple circuit meet the Barkhausen criteria?" 

Here goes: 

Even though it is a very simple circuit, it is worthwhile to separate out the things that it has to do: 

1) It needs to set the AMOUNT of feedback.    This is done by the tap on L1.  Too low down on the coil, and it is too close to ground through the .05 uF capacitor (not enough feedback).  Too high on the coil and you get too much feedback.  This is like an inductive voltage divider. 

2)  It needs to make sure that this feedback is in phase with the input signal. Positive feedback. Q1 is an inverting amplifier.  So it supplies 180 degrees of phase shift. As the signal at the base goes more positive, the signal at the collector goes more negative, and vice versa.  But we need an additional 180 degree shift to bring the output signal in phase with the input signal.  Here is the key:   The crystal provides the other 180 degrees of phase shift.  See

I tested this:  A 3.579 MHz crystal does provide the needed phase shift:  It introduces a shift of about 190 degrees.  Check out this very cool picture. The two scope probes are looking at the input and the output of the 3.579 MHz crystal with 3.580 MHz frequency coming from my HP sig gen. 

Click on the picture for a better view.

3) It needs to filter out other signals -- the 365 pf variable cap resonates with L1 at around 3.579 MHz.  This results in maximum circulating current through L1 at this frequency. 

4) It needs to match impedance to the antenna.  L2 wound over L1 forms the secondary of a transformer and efficiently moves the energy from the MMM to the antenna.  Think about the gears on your bike. 

The 10k resistor biases the base of the transistor, keeping it on.   The 27  ohm resistors limits the current through the transistor, preventing it from burning up. Note:  the 27 and 10k resistors should NOT be connected directly to each other.  There is no dot in the schematic. This causes some confusion among builders. 

The .05 uF capacitor does two things:   It grounds the L1/365pf tank circuit for RF (but not for DC).   It is less than 1 ohm at 3.579 MHz.   And it helps reduce (smooth out) key clicks (very sudden on-off changes in the oscillation). 
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column