F6CRP's FB Homebrew Receiver

I like F6CRP's homebrew receiver.  I like the way he presents it (block by block) and I like the inclusion of the W7ZOI IF board. The JF3HZB VFO is quite cool (even though it is digital),   We have posted about this VFO several times: 

 https://soldersmoke.blogspot.com/2022/05/who-is-jf3hzb-creator-of-that-nice.html

Denis has a very nice station and workbench: https://www.qrz.com/db/F6CRP

He also has some very nice videos on his YouTube channel: 

https://www.youtube.com/@radiorider8249/featured

Thanks Denis! 

Crushing Spurs with Better Bandpass Filters

PA3AKE's passband (on screen) an mine (on NanoVNA) 

While I was away in the Dominican Republic (3-9 August 2023),  I was thinking about spurs.  While there I watched Nick M0NTV's video about mixers.  The video was all great, but I was especially taken by the way he used a spectrum analyser to evaluate the output of various mixers.  This made me think that I should do the same thing with the output of each of my dual-band BITX rigs. 

I was especially worried about the output from my 17-12 rig.  The IF is at 21.4 MHz.  The VFO runs around 3.5 MHz.   So if you add the IF and the carrier oscillator signal you get to 12 meters.  If you subtract them you get to 17 meters.  But you need some good bandpass filtering to sufficiently knock down the unwanted output from the mixer.  And the BP filter should be sufficiently narrow to take out any remnants of the carrier oscillator signal. I had taken the easy way out and had used simple dual-tuned-circuit (DTC) filters.  I started to wonder if these simple BP filters would be enough to knock down the 12 meter signal while on 17 and the 17 meter signal while on 12.  I pulled out my NanoVNA to look at the passbands: 

Here is what the 17 meter DTC filter passband looked like. The cursor is at 29.6 MHz and you can see that near the 12 meter band it is only providing about 21 db of attenuation.  That is not enough. 

And here is what the 12 meter filter looked like. Here the cursor is at 18.150 Mhz and shows about 25 db of attenuation at this frequency.  Again, not enough.  

The results are as you would expect: I could see 24.9 MHz signals in the output when I was on 17 meters, and I could see 18 MHz signals in the output when I was on 12 meters.  The spurs weren't strong, but they were there.  I knew that more robust BP filters would help.  

At first I used the circuits prescribed by Martein PA3AKE.  He used larger toroidal cores, I used smaller T-50-6 (yellow) cores.  The results were very similar.  See the first picture on this blog post. 

The results were really good.  See pictures below.  I was using a TinySA with the signal fed through a 50 ohm 30db attenuator.  I was putting a 1 kHz signal in to the mic input.  

This picture shows the 12 meter output and the now non-existent 17 meter spur.  The cursor is at 18.142 MHz:    

This picture shows the 17 meter signal and the now non-existent 12 meter spur. The cursor is at 24.993 MHz.   We can see some second harmonic signal getting past the LP filter -- I will fix this.  

Then Farhan commented on Martien's filters, noting that they are all in the "LSB" configuration.   You can see from the charts below how they would be really good when you are trying to use the "difference" output from your mixer while knocking down the sum output,  but not vice versa.     So I built new USB filters for 12 meters,  and for 10 meters in my nee 15-10 rig.  I got better results on the two "sum" bands in my rigs (10 and 12 meters) 

The Art of Electronics #7 -- Paul Horowitz on Ham Radio, and on SETI (audio)

Radio Contact · “We didn’t find anything, so the search goes on”

Above is a seven minute audio podcast in which Paul Horowitz talks about ham radio and SETI. 

See also:  https://radiocontact.org/portfolio/paulhorowitz/

and  https://en.m.wikipedia.org/wiki/Paul_Horowitz

Sunburst and Luminary -- An Apollo Memoir by Don Eyles (video)

Buy the book from the Amazon link on the right side of the page >>>>>>>>>>>>>>>>>>>>>>>

There is so much great stuff in this 2018 video.  I am definitely going to buy the book.  This is another of those things that reminds me (a hardware guy) of the importance of software (Sunburst and Luimary were the names of two programs that Eyles wrote to enable the LEM to land on the moon).  

-- Asked about one of the biggest ancillary contributions of the Apollo program,  Eyles immediately says, "integrated circuits."   They used three terminal NOR gates.  Lots of them. 

-- They never had a hardware failure in the Apollo computers.  Demonstrating a classic troubleshooting technique, when they discovered what they thought was a hardware failure, they ran the program on another computer.  The problem was also there, so they knew there had been no failure on the first machine. 

-- The LEM simulator was very cool. 

-- Eyles' ability -- in two hours -- to write the code for the automatic landing program that Astronaut John Young was asking for, then have it flown on an Apollo mission to the moon was very impressive. 

Thanks to the MIT Museum for posting Don's talk.  And thanks to HackADay for alerting us to it.

Also, take a look at this one: https://www.youtube.com/watch?v=oi4h04ZgQsQ

And this:  https://www.youtube.com/watch?v=cmAc7t7tAlc

"The Art of Electronics" #6 -- Transistor Man

 

In the interview about "The Art of Electronics"  Lenor Fried had a shirt with "Transistor Man" on it.  

There he is (above), from page 63 of the second edition.  The authors explain: 

Click for a clearer view

Where can we get cool Transistor Man shirts just like Lenor's?  

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! 

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. 

"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. 

The Art of Electronics Post #3 -- The Element 14 Interview

 And here is a great interview with Element14: 

https://community.element14.com/learn/learning-center/stem-academy/b/blog/posts/element14-interviews-the-art-of-electronics-authors-paul-horowitz-and-winfield-hill

"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. 

"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. 

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!