Understanding Digital Radios

Alan WA9IRS writes: 

Hi Bill,

Thought I would drop you a brief note.  I have been catching up on my listening to past issues of Soldersmoke podcasts and was particularly interested in the discussion between you and Pete concerning the simplicity associated with non-digital, integrated circuits and microprocessors and all of the rest of the very small miniaturized circuit elements.  You rightly pointed out that you desired (along with a lot of the rest of us) to fully understand what was going on in a circuit and for that reason desired to maintain the simplicity of transistor and discrete components in your design and build projects. 

 I agree with you completely but offer the alternative to the simple circuits in the form of the attached simple diagram of the signal flow path in a digital radio. I found this some time ago in a digital electronics magazine and thought you and Pete would find it interesting.  Perhaps this might be something to spring on Pete on 4-1-2018.

Take care and thanks to both of you for many pleasant and thoughtful hours of enjoyment listening to Soldersmoke!

All for now, 73,

Allan,  WA9IRS

My response: 

Thanks Allan, Very illuminating.   It is all clear to me now.   I feel so much better.  FB OM.   73  Bill 

Circuit for Farhan's Satellite -- Arduino in SPACE

Farhan sent me the schematic of the AISAT amateur digital satellite that went into orbit on April 1, 2019 from India.   He notes that the circuitry is very simple.   Indeed, it reminds me of the very simple but effective circuitry we saw in satellites in the early days of the space age.  Beautiful simplicity, with an Arduino on-board.   And it is great to see that Farhan did not forget the low pass filter.  FB OM.  

Packets from Farhan's Space Ship

Farhan's AISAT flew over this morning.   Using HD-SDR software, an RTL-SDR Dongle,  and my Dominican Republic refrig tubing quad I was able to capture some the packets.  Above you can see one of them, floating like a flying saucer in the waterfall.  Pretty amazing that that signal came from a machine put in space by our friend Farhan.  

Congratulations to Farhan on New Amateur Satellite Launched 1 April

This is not an April 1 trick.  Farhan and Exseed Sat have put another bird in orbit.  
Details here: 
http://amsatindia.org/

This site in Argentina gives pass information: 
http://amsat.org.ar/pass?satx=aisa1

I will be listening tonight! 

Congratulations Farhan! 

More info: 

https://www.isro.gov.in/launcher/pslv-c45-emisat-mission

https://makeinhyderabad.com/private-satellite-with-hyderabad-origin-aisat-starts-off-well/

Malicious Code in the Si5351 -- Pete quitting podcast

Those of you who have been reading Pete N6QW's blog (and all of you should be reading it!) will have seen a recent post about his efforts to modernize (digitize) the VFO in an old tube-type Ten Tec Triton IV model 544.  Pete complained that --oddly -- in spite of replacing the old analog tube-type VFO, the rig with a modern, rock-stable Si5351 VFO, the old rig CONTINUED TO DRIFT.  That had Pete and a number of us scratching our heads.  How could that be?  

Pete then completely removed the Si5351 VFO from the old boatanchor.   Sitting on his bench, all by itself, THE DAMN THING EXHIBITED ALL THE CHARACTERISTICS OF ANALOG VFO THERMAL DRIFT.  Wow!  Why?  Pete was really pulling his hair out on this one. 

We immediately began to see if others were getting the same results.  Nope.  None of our Si5351 VFOs were doing this.   This was REALLY strange.  

At this point we had to turn to a real Arduino expert, a guy who I had met during my time in Italy: Luigi Bugiardo from the Arduino research center in Bocalupo, Calabria.  Pete gave him remote access to his computer and he began to poke around.  

It didn't take long.  Luigi quickly found the problem:  He found several lines of malicious code "embedded in the Si5351.h and si5351.cpp files –sort of lurking out there and not easy to spot." 

Pete then removed this code and -- BINGO -- no more drift.   

Now I know some of you guys are thinking that this was just a bit of harmless fun.   But Pete is really angry about this.  He feels like he has been played for a sucker by some ham who was pretending to collaborate with him.  Pete sees this as yet another violation of the unwritten ham code of conduct.  To him this is another intrusion of computer/hacker noob hazing into the ham radio world.  And worst yet, he thinks this malicious code came to him because of this involvement in the podcast and his blog -- that participation resulted in the widespread exposure that got him into this mess.  

Pete is so upset that he has vowed to drop out of the podcast and shut down his blog. 

So come on fellows.  It is time to 'fess up.  If you did this, or if you think you know who did this, please send an e-mail to me at soldersmoke@yahoo.com   I think being able to pinpoint the prankster will help Pete deal with this whole thing, and hopefully get him back into the SolderSmoke...   

So Much Cool Stuff on Pete N6QW's Blog

There is so much tribal knowledge, so many good ideas.  Be sure to visit Pete's blog regularly.  

http://n6qw.blogspot.com/

He needs the meter from an SBE-33.  Somebody out there must have one.  

Check out his stepper motor antenna tuner video.  

And be sure to leave some comments or to send Pete an e-mail with feedback.  I live in fear that he will think no one is reading and then stop posting.  We can't let that happen!  

Apollo 11 -- The Documentary

My wife is a kind and tolerant person.  Proof of this is that she went with me to see the Apollo 11 documentary that we recently posted about.  

I think you have to be a geek and/or have The Knack to really like a 90 minute documentary with no audio other than Walter Cronkite's reporting and the recorded dialogue among the participants.   But of course, I loved it.  Amazing video, especially of the Saturn V.  

Bob Scott KD4EBM found this great interview with the film maker: 

Video:

https://www.tested.com/science/space/869951-apollo-11-still-untitled-adam-savage-project-31919/

Audio only (downloadable)

https://d2rormqr1qwzpz.cloudfront.net/podcast/stilluntitled_20190319.mp3

Amazing New Geostationary Amateur Satellite -- LISTEN ONLINE!

Wow, quite a step forward in the amateur satellite world.  Qatar and AMSAT-Germany have collaborated to put an amateur radio repeater in geostationary orbit.  That's pretty amazing.  Read more here: 

https://hackaday.com/2019/03/18/eshail-2-hams-get-their-first-geosynchronous-repeater/

Read about a group of Norwegian students working on a satellite station for this bird: 

https://www.la1k.no/2019/02/20/getting-ready-for-e%CC%B6s%CC%B6%CC%B6h%CC%B6a%CC%B6i%CC%B6l%CC%B62%CC%B6-qo-100-part-2-how-we-did-it/

And this is really fun:  LISTEN TO THE DOWNLINK LIVE VIA WEBSDR! 

We can't hear this thing from North America -- it is flying over the Congo.  But stations in its footprint are putting their receivers online -- you can listen to the 10 GHz downlink via WebSDR: 

UK WebSDR:   https://eshail.batc.org.uk/nb/

Brazil WebSDR:     http://appr.org.br:8902/

DISAPPOINTED! No Takers on Mechanical Filter Question! SAD!

So, in our last podcast I asked the group to take a look at two pictures of a mechanical filter that I had recently taken out of its case.   These pictures appear above and below. After a discussion of magnetostriction,  I asked the group if they could spot anything unusual about this particular device. 

I expected many responses.  What did I get?  CRICKETS!!  What is wrong with you guys?  Are you spending so much time with software and FT-8 and lines of code that you can't deal with a simple analog question like this?  SAD! I guess I will have to answer the question myself.  Scroll down. 

The diagram below presents the conventional Collins arrangement for a mechanical filter.   Note that at the input and at the output there is a coil.  This coil creates from the signal a varying magnetic field.  Because of the principle of magnetostriction, this field causes the resonators/rod assembly to flex and vibrate, much like a musical tuning fork.  At the output, this means that inside the core of the output coil there is a piece of metal vibrating at the signal frequency.  This will produce an output signal.  

But take a look at my little mechanical resonator.  Where are the input and output coils?  

THERE ARE NONE!  See those little rectangular things at either end?  Those are piezo-electric crystals that are MECHANICALLY connected to the disc/rod assembly.  So when the signal comes in, it is applied electrically to the piezo material which then physically vibrates. This vibration passes through the filter and to the piezo device at the other end. There the mechanical vibration results in an electrical signal at the output.  

So, I think it is time for you all to hang your heads in shame. Perhaps go to the doctor to see if you still have The Knack. Ask for forgiveness from the radio gods.  

We have lost our spiritual leader: George Dobbs G3RJV, SK

Yesterday we received the very sad news that George Dobbs, G3RJV has died. 

I think it is no exaggeration to say that with George's passing, we have lost our spiritual and  philosophical leader.  The founder of the G-QRP Club and Editor of our beloved SPRAT journal, George took his strong technical skills and his talent for writing and combined it with the wisdom about life that came from his religious vocation. He was a prolific writer and speaker, and in all his work you will find a unique combination of the technical and the philosophical.  Not only did he teach us how to build our own rigs, but he taught us why we should build them.  

We talk a lot about tribal knowledge -- George was definitely the source of much of that.  But he went beyond that and also became a major source of what we can call tribal wisdom.  He was one of our tribal elders. Instead of speaking to the tribe around a roaring fire, George spoke to us through SPRAT, through articles in other ham magazines, through his books, and through his talks at rallies and hamventions, many of which have been preserved in YouTube videos.  George's friend Tony Fishpool sent us the one embedded below. 

We are of course very sad to see George go, but we can all take comfort in the fact that he will -- through his writings and through his recorded talks -- remain with us. For years to come people who feel a strange urge to build their own radio equipment will find themselves reading George's work or listening to recordings of his melodious voice.   They will find there not only the needed technical information, but also the encouragement and tribal wisdom needed to carry on.  There will be a bit of George Dobbs in all their rigs.  In that way G3RJV will stay on the air.  And I know that George would be delighted by that.  

73 G3RJV.     

Viking Rigs Save the Day!

I attribute the success to the Times Sequence Keying.  And, of course, to the analog VFO.  

Thanks again to Jeff Murray. 

SolderSmoke Podcast #210 Boatanchors, Magnetostriction, VFOs, AM, CW, SSB, Mailbag

2 March 2019 

SolderSmoke Podcast #210 is available: 

http://soldersmoke.com/soldersmoke210.mp3

Alexa, Marie Kondo, berets, and ham radio

Bi-Coastal Boatanchors
BATTLE CRY: The Vintage SSB Preamble! "We are NOT ashamed!" 
Bill's HT37 and Drake 2B 
Pete's National National NCX-3  TRGHS
Mechanical Filters
Magnetostriction
Why did Collins go with mechanical vice crystal filters? 
The foam deterioration syndrome in mechanical filters.  Sad. 
Please send any unwanted Mechanical Filters to Bill. 
BONUS QUESTION:   Look at the filter below.  What is different/special about this one?

Pete's antenna trouble
Pete's FB amplifier troubleshooting
Recent improvements in the uBITX finals
Pete's design for a VFO for Bill (and an indoor antenna tuner!)

Bill's VFO for Pete:  HRO dial and gearbox driving a rotary encoder

Guido PE1NNZ puts the QCX on SSB
"The Secret Life of Machines -- Radio"
HB HRO dial from DL6WD
WA1QIX's USB D-104
"The High Frequency Oracle" 
DeMaw's LC filter receiver
Godzilla and Ham Radio
Bill's poor quality SSTV images from space (what happened?) 
Listening to AM on an SSB receiver
Mixed feelings about CW 

MAILBAG
M0KOV's mom took him to the doctor due to THE KNACK. 
M0JGH getting married (ALWAYS LISTEN TO PETE!) 
Jac's FB Receiver

What is different/special about this one?