SolderSmoke Podcast #229 -- G2NJ Trophy, SDR, HDR, CW! Mailbag

Soldersmoke Podcast #229 is available: 

http://soldersmoke.com/soldersmoke229.mp3

--  G2NJ Trophy is awarded to Pete Juliano, N6QW. 

 -- Get your vaccine shot as soon as you can!  

-- More from "Conquering the Electron" by Derek Cheung. 

-- Bad fire in the chip factory.  Such a shame.  Sad!  I had NOTHING to do with it.  I was home that day.  I can prove it.

 -- Bezos is not such a bad guy.  Turns out he is a space-geek.  

 -- Perseverance was the big space news.  Very cool.  

 

Pete's bench:

Raspberry Pi vs. Microcontrollers

Treedix display

Conversion of the Dentron Scout

CW rigs?

6L6 on a wooden chassis

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Bill's bench: 

Hodgepodge:   

-- BITX40 Module.  

-- Ramseykit Amp. 

-- San Jian counter,  

-- CW using 750 Hz oscillator. 

-- RF-actuated piezo buzzer.  

-- SDR!  SDR using PC and tablet.  

-- Checking the output with SDR.  

-- Moving the carrier osc frequency.  

 Also, I put the Fish Soup 10 back on the air.  Nice contacts under 200 mw.

Up next:  A rig for 80/75 and 20 meters.  Single Conversion.  Using VFO from a Yaesu FT101 that runs 8.7 – 9.2 Mhz.   Quiz question:  What IF should I use?

MAILBAG

Mark Zelesky sent me wood tokens with power and Ohm's law formulae.  Thanks!

Scott WA9WFA Built a really nice Mate for Mighty Midget RX – getting it going!

Tryg EI7CLB found board of his George Dobbs Ladybird RX.  Rebuild it OM!

Tom WX2J – We talked about “No lids, no kids, no space cadets” nastiness.

Nick M0NTV about sideband inversion.  I like the simple rule about subtraction.

Jonathan M0JGH – Always listen to Pete.  Got married, has mixing product. Leo?

Mike AE0IH.  Dad used a BC-348 in the service. Looking for one.  FB.

Adam N0ZIB – “Silent Shep” site --- with some ham radio shows I had not seen.

Walter KA4KXX in Orlando has a similar subtraction problem with San Jian counter.

Bill N5ALO sent me a really nice KLH speaker.   I’m using it now.

Jason N2NLY – interested in building SSB transceiver.  One step at a time OM…

Trevor in Annapolis sent xcsd cartoon that really hit home. 

Farhan is doing OK in India, diligently protecting his family from the virus.  

Peter VK2EMU also doing well.

Dave AA7EE Casually killed a DC receiver in Hollywood, and disposed of the remains. 

Charlie ZL2CTM doing great things with simple SSB.  Blogpost.

Phil VK8MC in Darwin sends article on "Mend not End" battle against planned obsolescence.

Bob KY3R re my SDR adventures, asked if I’ve had a recent medical/psychiatric evaluation. 

Hodgepodge: Tablet SDR with a Bluetooth Mouse (video)

I continue to find things in the shack that I can connect to the Hodgepodge.  Here it's an old Android tablet with a Bluetooth mouse.   

The waterfall is pretty, but this addition just shows why SDR is really TOO easy.  The modified RTL-SDR dongle is doing direct sampling, so there is not even any phasing circuitry to tinker with.  All the filtering and sideband selection is happening in software inside the 40 buck Android tablet.  The results look nice, but I don't find it very satisfying -- all I did was connect some cables.  So it's back to HDR for me. 

A REALLY Cheap Receiving Rig

Wow, lots of ingenuity in this 1921 receiver.

-- Has anyone actually made a diode out of a light bulb in the way described? 

-- The antenna coupler on the table leg is not much different from the tuner that I have attached to the wall of my car port. 

-- Note that when our hero finishes the receiver, he is able to pick up signals from Mars!  FB OM. 

Who will be the first to recreate this 1921 receiver? 

Aladdin's Lamp == The Vacuum Tube (aka The Thermatron) (Video)

After our posting of the video about 1957 transistor production, our friend Peter O'Connell VK2EMU asked for some equal time for vacuum tubes.  He sent me this 1940 Western Electric video.  It is quite interesting. 

-- I like the Aladdin's lamp metaphor.  When I was out in the Azores I thought of my homebrew 17 meter DSB rig as my "magic carpet." 

-- Lowell Thomas was brought in to narrate.  His voice sounds a lot more natural than that used to narrate the transistor film. 

-- To explain the effectiveness of transcontinental telephony with vacuum tube repeaters, they compared the system that of a relay of "hog callers" claiming that it would take 100,000 hog callers to carry a signal from New York to San Francisco.  So perhaps this could be a rival to db?   100,000 hc? 

-- Arlington to Paris 1915 caught my eye -- Arlington Va. is right down the road. 

-- The film of Edison in his lab was good to see.  And note the importance of his lab notebooks. 

-- The explanation of thermionic emission was quite good.  But of course too much credit was given to Lee DeForest. 

-- The breathless description of the amazing uses of tube technology was for me a reminder of how recent this technology is.  My father started as New York City cop in the 1950s.  He always referred to his police car as a "radio car." 

Hey, are any radio amateurs out there using one of those big water-cooled tubes?  If not, why not? 

A Homebrewer

 

That is Homer Price, the lead character in two books by Robert McCloskey, published in 1943 and 1951.  The thing in the valise is Homer's pet skunk.  Of course. 

More info here: 

https://en.wikipedia.org/wiki/Homer_Price?fbclid=IwAR2cRUCurQBXaP-m4LdPFBOnBU4nvgZwtOZqrAzF8MaGvS4Xb_eTWHSWE2E

Homer is clearly a fellow we need to know more about.  I have ordered the book. 

Making Transistors in 1957

Thanks to Thomas K4SWL for alerting us to this video -- he had it on his excellent SWLing Post blog. 

Many things crossed my mind as I watched this video: 

-- Pocket protectors!  Pete recently noted that this was a common fashion accessory among electronic techs and engineers back in the day. 

-- HP test gear. 

-- "Extreme cleanliness" that doesn't seem quite so clean.  

-- 550 transistors per hour.  Now we have upwards of 50 billion on a single chip. 

-- The Germanium salami that Pete mentioned in our last podcast. 

-- Hints of Silicon's impending replacement of Germanium. 

-- A transistor factory in Spring City, Pa. that "hums with excitement" (seemed kind of sleepy). 

-- The 1957 assumption that Philco transistors would be in the first orbiting satellite.  Then came Sputnik.

-- The transistor that moves like a "Gulliver through Lilliputian lands."  

-- Our voices or accents seem to have changed, at least the voice used in products like this.  No one talks that way today. 

-- As I watched, I tried to remember if Pete's CK722 was made by these folks.   But no, that was a Raytheon product.   Here is a nice short description of the early days of the CK722:   https://en.wikipedia.org/wiki/CK722   We need to learn more about the hobbyist Carl Todd.

The Secret Life of LEDs -- A new Tim Hunkins Video

Thanks to Tony G4WIF for alerting us to this really nice video from the fellow who made all those great "Secret Life of Machines" videos.   This video on LED's makes me want to improve the lighting in my work shop.  And I think I need some more high wattage resistors.   I'm really glad Tim Hunkins is making more videos.  His look at the Secret Life of  Radio was a real masterpiece. 

Hodgepodge: Moving the Carrier Oscillator Frequency (and a Flashback to 2002) (Video)

As explained in the video, in the course of using my RTL-SDR dongle I noticed that the signal being put out by my Hodgepodge rig had some problems.  There was poor opposite sideband rejection, and in terms of audio quality I has putting out too many lows and too few highs.  I figured the problem was the result of the carrier oscillator frequency being a bit too low, a bit too close to the flat portion of the crystal filter passband.   I needed to move that carrier oscillator frequency up a bit. 

BITX40 Module BFO 

In the actual BITX40 Modules, L5 was replaced by just a jumper wire, and the C103 trimmer was not on the board.  Farhan and his team instead selected X5 crystals to match the passband of the 12 MHz crystal filter. Mine was originally at 11.998653 MHz.  But I wanted to tweak mine a bit -- I wanted to move it up about 500 Hz.  Reducing the capacitance would move the frequency up. Putting capacitance in series with C102 would have the effect of reducing the capacitance in the circuit.  I just removed the jumper wire and used the holes for L5.  First I put in a single 30pf capacitor.  This dropped the capacitance between X5 and ground to 18 pf.  That resulted in too large a shift.  So I added another 30 pf cap in parallel with the first one.  This resulted in a total capacitance from X5 to ground of 26 pf.  This was about right -- the carrier oscillator/BFO frequency was now 11.9991 Mhz.  I had moved the carrier oscillator frequency up by 447 Hz -- just about what I was hoping for.  

This was a very satisfying fix.  it was a chance to put to use experience with other SSB rigs, to make use of the RTL-SDR dongle as a diagnostic tool, and to tinker with the BITX40 Module in the way that Farhan had intended for it to be tinkered with.  

I'd done this kind of adjustment before, but without the benefit of an SDR display.  Below is the story of one such adjustment. 

---------------------------------

A Flashback to 2001-2002

(From my book "SolderSmoke -- Global Adventures in Wireless Electronics")

Now it was time for some debugging and fine tuning.  I needed to make sure that the frequency of the carrier oscillator was in the right spot relative to the passband of the crystal filter.  If it was set too high, the filter would be chopping off high notes in my voice that were needed for communications clarity, and it would allow too much of what remained of the carrier (residuals from the balance modulator) through. If it was set too low, the voice signal transmitted would be lacking needed base notes.  I didn’t have the test gear needed to perform this adjustment properly, but my friend Rolf, SM4FQW, up in Sweden came to my aid.

One night, during a conversation with Rolf, I explained my problem and he offered to help me make the adjustments… by ear.  Performing an electronic version of open-heart surgery, with power on and Rolf on frequency, I opened the case of the new transmitter.  The carrier oscillator has a small capacitor that allows the frequency of the crystal to be moved slightly.  With Rolf listening carefully, I would take my screwdriver and give that little capacitor a quarter turn to the right.  “Better or worse?” I would ask. 

I think this little adjustment session captures much of the allure of ham radio.  There I was, out in the North Atlantic, late at night hunched over a transmitter that had been forged from old Swans and Heathkits, from cell phone chips, and from bits of design from distant members of the fraternity of solder smoke.  Pericles, the source of many of the key parts, was gone.  So was Frank Lee, the amateur whose SPRAT article had inspired the project.  But Rolf and I carried on with the core tradition of the radio fraternity: hams help their fellow hams overcome technical difficulties.  

Straight Key Night 2021 at SA2CLC in Sweden

Wow, check out the FB gear of Tommy SA2CLC in Sweden, in use on Straight Key Night 2021. There is some German WWII gear,  a BC-348,  a homebrew transmitter, and some FB QRP kits. 

More on Tommy SA2CLC here: https://www.qrz.com/db/SA2CLC 

The culvert under the road for coax to the antennas is very cool. 

FB Tommy!  A belated HNY to you OM. 

Taking Care of an Old Analog Machine -- The Scanimate

Of course, I understand and sympathize completely.  

Thanks for Rogier PA1ZZ for sending this.  

AA7EE Casually Kills a Direct Conversion Receiver, then Coldly Discards a Diode Ring Mixer

I was really glad to see that Dave AA7EE has -- after a long absence -- posted another article on his blog.   The article has some great personal reminiscences about his involvement with direct conversion receivers.  Here is one passage: 

I spent many happy hours tuning around and listening on 80M with the DSB80. It was this first experience that cemented my affinity for direct conversion receivers built with commercially available diode ring mixer packages. It just seemed so simple – you squirt RF into one port, a VFO into the other, and (after passing the result through a diplexer) amplify the heck out of the result. The seeming simplicity of the process of converting RF directly to baseband audio has held great appeal for me ever since. Unfortunately, that project didn’t survive. One day, in later adulthood, in my apartment in Hollywood, I reversed the polarity of the 12V DC supply and, discouraged at it’s subsequent refusal to work, tossed the whole thing away. Now, I cannot quite believe that I did that, but it was during a long period of inactivity on the ham bands, and complete lack of interest. If only I could go back, and not have thrown it into the dumpster of my apartment building! Hollywood is ridden with recent notable history. My little double sideband transceiver met it’s unfortunate end just 100 feet from the spot where Bobby Fuller, of The Bobby Fuller Four, was found dead in his car, in 1966, the subject of a still unsolved mystery to this day. The death of my little DSB rig was a lot less mysterious. To think that I heartlessly tossed an SBL-1 mixer into a dumpster, is a mark of how far I had strayed from my homebrewing roots, forged in a little village in England. Now, a few years later, in a city known for it’s sin and excess, I had cruelly ended the life of a stout and honest diode ring mixer. I suppose I should spare a thought for the polyvaricon but, well, you know – it was a polyvaricon!

  https://aa7ee.wordpress.com/2021/03/04/the-ve7bpo-direct-conversion-receiver-mainframe/

EXORCISM! 40 Meter RFI Problem Resolved

BEFORE

David W. suggested I use my RTL-SDR dongle to look for the source of the 40 meter RFI that I have been mentioning.  (It appears as an ugly stipe in the waterfall of my Hodgepodge transceiver.) So I fired up the RTL-SDR -- there were the tell-tale spikes, spaced neatly every 50 kHz.  The ARRL Handbook says this is typical of a switched power supply.  Before I started patrolling the neighborhood with a tin-foil hat and a portable receiver, I decided to check my own house for any recently installed electronic devices.  It didn't take long -- when I unplugged the new (mid-pandemic) treadmill the spikes disappeared.  This treadmill was located about ten feet above my rigs, and between the rigs and the antenna.  Duh.  I should have thought of this earlier. Mystery solved.  Thanks David. 

AFTER

ZL2CTM's Simple SSB Transceiver

Congratulations to Charlie Morris ZL2CTM for his first contact with his Simple SSB rig.  

There are so many cool things in Charlie's video, starting with his mention of having been woken up early (2 am)  by the very strong earthquake off New Zealand.   Exhibiting true homebrew spirit, Charlie apparently went straight for the shack and worked on his rig.  FB OM. 

Al fresco!  I love the spacious layout on the board and the obvious division into stages.  And I like the wooden board that holds it all together. 

I like the idea of two bandpass filters -- this is simpler than switching one from transmit to receiver.  

Hooray!  Homebrew diode ring mixers!   Yes! 

I think Charlie follows the UK convention with his T/R switch -- they have up as off.  I may be wrong but I think most US homebrewers have up as on, and up as transmit.  Cultural differences. 

Notice Charlie touch-testing the heatsink during that first QSO.  We all do that. 

I like the 24 volts on the IRF-510 drain.  Allison always said that IRF-510s run better at 24V than they do at 12V. 

Of course I disagree a bit on the issue of analog VFOs. But this is just a matter of personal circuit preference. 

Charlie's calculations and notes are really wonderful.  His candid discussion of impedance matching is especially useful.    I think his use of loose-leaf  sheets of paper is wise and it paves the way for a useful folder for each HB rig. 

Here is the introductory video for Charlie's Simple SSB project: 

https://www.youtube.com/watch?v=BgQUG0AImKY&list=PLxU5OX0SLgIPdYj_MZG03CeimbRU6Btml

Here is Charlie's 10 part video series on his simple SSB rig: 

https://www.youtube.com/playlist?list=PLxU5OX0SLgIPdYj_MZG03CeimbRU6Btml

And here is Charlie's YouTube channel: 

https://www.youtube.com/c/CharlieMorrisZL2CTM/videos

Thanks Charlie! 

Over the Waterfall into the Dark Side: Hodgepodge SDR

This one's for Pete. My effort to add features and modes to my Hodgepodge transceiver took a dramatic turn when I connected the rig to my computer via an RTL-SDR dongle. Woohoo! A Hodgepodge waterfall! Check it out.

The dongle was modified for direct sampling at HF. In the box with the dongle I have one amplifier stage, consisting of a 40673 dual gate MOSFET and one parallel tuned circuit, now tuned to the Hodgepodge IF of 11.998 MHz. I tap the the Hodgepodge's BITX40Module at the output of the first mixer, just before the crystal filter. This was a lot of fun. I can even check my own signal on transmit! This is like having the best of both worlds.

"The Secret Life of..." Tribal Knowledge!

It is great to hear that Tim Hunkins is producing this new series.  It looks like it will be largely about "know-how" -- about what we'd call "tribal knowledge." 

The SolderSmoke Team Talks to the River City Amateur Radio Communication Society (Video)

Pete and I had a great time speaking to this really nice California ham radio club (video of the event appears above).  Special thanks to club president Dr. Carol Milano, MD.  Wow, what an impressive person and ham radio operator she is:  https://www.qsl.net/kp4md/#New%20York

This club is doing a group build of a version of the famed Tuna Tin Two.    I mentioned that I had held the original TTT in my hands, and that Rex Harper had conducted a "Mojo Transfer Ceremony" that imparted TTT Mojo to my BITX17 transceiver (which was also discussed).  I promised to share the video of that momentous event.  Here it is: https://youtu.be/9RZRaFUtTcc

Thanks to Carol and the members of the RCARCS.  This was a lot of fun.  

A Frequency Counter for the Hodgepodge -- An Analog Solution to a Digital Problem

Imagine my dismay when I discovered that I could not use my $5 San Jian PLJ6-LED frequency counter with my Hodgepodge transceiver.    The problem is described here: 

http://soldersmoke.blogspot.com/2021/02/a-problem-with-san-jian-plj6-led-counter.html

This video describes my solution.  I took some pleasure in using an analog solution to solve a very digital problem.   I know this could have been fixed with one or two changes to lines of code, but I liked doing it this way.  This was all kind of fun, and it allowed me to use yet another bit of circuitry that was sitting idle in the shack.  That is the whole point of the Hodgepodge project.  

The best is yet to come.   Especially for those of you who like waterfalls.... Stay tuned. 

Novice Rig Roundup -- This Year in Memory of Bry AF4K

 

Bry was a good guy and one of our sponsors.  RIP OM.  And the Novice Rig Roundup was his thing. 

http://ve7sl.blogspot.com/2021/02/here-comes-2021-novice-rig-roundup-nrr.html

Putting the Quarantine Hodgepodge Rig on CW (Video)

Putting this rig on CW posed a real Hodgepodge challenge: What did I have laying around that would let me do this? Then I remembered: Years ago I built a little 750 Hz audio tone generator. So I pressed that into service. I also needed a sidetone so I built a little RF-actuated circuit that turns on a piezo buzzer when I go key down. And I put a little DC monitoring device (recommended early in 2020 by the Ham Radio Workbench podcast) between the power supply and the rig. There is more to do! Stay tuned.

Jean Shepherd Goes to a Hamfest -- And Much More

Here is something nice to listen to in your shack...  

I hadn't heard this one before.  It is about Shep's teenage trip to a hamfest, but it also about his youthful enthusiasm for ham radio and electronics.  Many of us can identify with this very easily. 

He talks about what must have been a very early use of "blue boxes" -- the audio tone generators that allowed young miscreants (including the Woz) to make long distance phone calls for free. I wish I had gotten into this.  It sounds like fun. 

He talks about how painful it was to be on phone (AM phone) with just 2.5 watts homebrew, when everyone else was running a lot more power. 

And wow, they played a baseball game at the hamfest.   Phone guys vs. CW guys. 

I won't spoil it by telling you the results of the hamfest raffle.  

Update from the Wizard of Wimbledon -- "Always listen to Pete"

In a recent podcast, Pete mentioned that Leo Sampson (the young Brit who is rebuilding the sailing yacht "Tally Ho") should seal the deal with his girlfriend.   Well, it seems that "life coach" should be added to Pete's already impressive list of abilities (homebrew hero, pasta chef, guitar player, etc.)  A while back Pete gave similar advice to Jonathan, M0JGH.   This morning, Jonathan reported in, confirming that Pete's advice was completely correct.  A "mixing product" arrived early in the lockdown. Congratulations to Jonathan and his remarkably radio-tolerant wife.  It seems Leo should be shopping for a ring. 

--------------------------  

Dear Bill and Pete

I hope that you and your families are staying very well during these extraordinary times.

I wanted to thank you both for the reminiscent shout-out during the last podcast, whilst you were suggesting that Leo Sampson of sailing yacht Tally Ho should "seal the deal" with his girlfriend. If our case study is indicative of his future prospects, he absolutely should do! Not only are we happily married but we welcomed a bubbly baby girl into our family at the start of lockdown. (I note that hams refer to children as “harmonics”, but wouldn’t mixer products be a more appropriate metaphor?) 

Apologies for my radio silence of late. Circumstances have allowed me the rare and special opportunity to take more of a lead with parenting, and so my soldering iron has only been wielded for maintenance purposes rather. Your discussion about the intrigue of distant voices emerging from homebrew rigs has whetted this CW addict's appetite to build something for SSB or even DSB, and likely for one of the higher bands...

I feel that I should briefly stick up for the art of CW, though. As a keen amateur musician the ability to communicate through rhythm will always hold a special charm, particularly when you consider that many of my regular EU chums on 40 and 80 are easily identifiable by their “distinctive fists”. I recall a true WW2 spy story in which a double agent, I forget which, was rather unwell but still had to be carried into the radio tent to send his CW whilst lying on a stretcher, otherwise the Germans might notice the absence of this distinctive fist and realize that the game is up!

73 from Wimbledon

Jonathan

M0JGH

EI7CLB's Ladybird Receiver (George Dobbs Design), and Voice over the Internet

 

I suggested that Tryg once again gather the parts to build George Dobbs's Ladybird receiver.  He should use the same wooden base.  That would be great.  

As for VOIP, I told Tryg that SolderSmoke got its start in a VOIP program  called Echolink -- Mike KL7R and I used to converse from London to Alaska.   Mike recorded one of  our conversations, and that became SolderSmoke #1.  I was using VOIP even before that -- from the Dominican Republic in the mid 90's I was connecting my Radio Shack 2 meter HT to an early VOIP program Internet  Phone or I-phone.  The company that made it was an Israeli firm called Vocaltech.   

---------------------------

Hi Bill,

Thanks for the recent emails and podcasts. I have attached a picture of my first radio - or at least what is left of it. I plundered it for parts down through the years as you can see. It is the build from the late Reverend George's "Making a Transistor Radio", the Ladybird book that really put the hook in me all those years back. I was probably only 11 when my late Grandmother and I went to Dublin by train (300 mile round trip) to Peats of Parnell Street to buy what components my pocket money could afford in order to build the first couple of stages of the radio, The wooden base was cut for me by a worker at a local furniture making factory here in Galway. He got a great laugh out of it when I told him I was going to build a radio - he kept putting the wooden blank up to his ear and joking: "I can't hear anything yet!". I will always remember it.

On another front I wanted to thank Pete and yourself for an entertaining and informative couple of podcasts. I made the leap a couple of months back and bought a set of boards for a uSDX (W2CBA version) but I may just use it as a receiver if I ever get around to building it. I don't know yet. The kit that Pete mentioned in episode #228 really got me excited. I expect you can imagine that my imagination is running riot at the moment.

Finally, I would be interested to hear about your take on half duplex VOIP apps such as Peanut. I realise that it is not 'real' radio to many but I have enjoyed several contacts with operators around the world with it and it has been quite satisfying. These ops that I have spoken with have often been infirm, elderly or have mobility issues. There are also a couple that are under HOA restrictions. One OM in particular lives in a retirement village and is a full-time carer for his wife. I think it is a good thing that they can still be involved in radio without all of the physical demands it might make on them or annoying their neighbours. It might, at least, it might be a worthwhile topic for discussion. Thanks again for an excellent Podcast. BTW, I am a bit of a guitar nut too - is that a Stratocaster that Pete is holding in the picture on the Soldersmoke Blog Page?

Right ho, time to put the kettle on. Tea is a vital component for operational efficiency in my radio world!

73,

Tryg de EI7CLB

Quarantine Hodgepodge Rig -- Part 1 (Video)

More videos to follow.  I have added features, and a transmission mode.  Stay tuned.  

Awesome Video of Perseverance's Landing on Mars

When we watched the landing on February 18, Elisa kind of complained that they were using simulations -- like the rest of us, she has come to expect actual video of important events.  Well, now we have it.  Actual video of the parachute deployment, the decent, heat shield separation, dust from the Sky Crane rockets, the whole thing.   Wonderful!   See above. 

The full press conference is worth watching:

Here we learn that the placement of these cameras was inspired by the sports camera that enabled one of the NASA/JPL guys to watch his daughter's gymnastic back flip from her perspective.  As they discussed the images from the spacecraft,  I found myself thinking of my little Astrocam Estes rocket in the Dominican Republic, our kite-camera adventures in the Azores, and the key-chain video camera that Billy and I flew on a rocket in the Shenandoah Valley. 

We also learn that the parachute color pattern contains a hidden message... (see below for the solution, worked out by a fellow in France.) 

One of the JPL guys noted that we've all had a tough year, and he hopes that these images will bring some joy to people.  Indeed. 

And wow, there are microphones!  They show the mic in the press conference video, and they play audio of the sound of Martian wind. 

There was a nice shout out to Sojourner from 1997 (the year my son Billy was born).  

------------------------------

Someone cracked the code in the parachute coloration: 

"DARE MIGHTY THINGS"

and the JPL Coordinates

https://twitter.com/FrenchTech_paf/status/1363992051734478852

LA6NCA's German Military WWII Receivers, and a Luftwaffe Receiver with FAST QSY

Discussions of old military radio gear are dominated by talk of U.S. radios.   Yesterday in the comments section of the SWLing Post I found two interesting videos about German WWII equipment.  Above you can see LA6NCA's receivers.  Below there's a video of a Luftwaffe receiver with an amazing capacity for really rapid frequency change.  

Bootleggers! Radio Criminality -- Some Jean Shepherd Stories

Thanks to Adam N0ZIB who alerted me to Shep's Cincinnati story about the stolen AM broadcast station.  I then found another YouTube video that had that story, but preceded by an even better tale of ham radio bootlegging.  

Adam found his story on this fantastic YouTube channel -- a collection of Shep stuff: 

https://www.youtube.com/channel/UCaip8PM6hvPdKsbID0DNaMA  

Thanks Adam.  73  and EXCELSIOR! 

Perseverance gets to Mars with Parachute and Sky Crane

 

Perseverance under parachute canopy

Perseverance hanging from rocket-powered Sky Crane. 

We had another picture of a spacecraft parachuting to Mars: 

It was from the Phoenix lander in 2008: 

https://soldersmoke.blogspot.com/2008/05/parachuting-on-mars.html

The Sky Crane picture is also awesome, but having spent some time under canopy, I am especially fond of the parachute photos. Dino KL0S and Kevin AA7YQ know what I'm talking about.  And Mike WA6ARA used to design and test parachutes for NASA at the Jet Propulsion Laboratory.  

My affinity for parachutes probably predates my jumping.  My Estes rockets usually returned to earth by parachute (sometimes they used the more economical "streamers").  And my grandfather had a little kite contraption that would send a parachute up to a kite where the device  would hit a cork on the line and release the parachute.  He used to attach a dollar bill to the toy parachutist for the kids in the neighborhood.  Decades later, my dad got one of these, and we frequently flew it during beach vacations.  So I like parachutes.   

AIRBORNE! 

A Step Closer to the Elser-Mathes Cup? Ham Receives Signals from Mars

 

That is the antenna that Scott Tilley VE7TIL  used to receive signals from the Chinese spacecraft Tianwen-1 in orbit of Mars.  In a recent SpaceWeather article, Scott comments on the importance of SDR receivers in these deep space reception efforts.  

https://spaceweatherarchive.com/2021/02/16/ham-radio-signals-from-mars/

I've been watching the Elser-Mathes cup for a long time. I dedicated my book "SolderSmoke  -- Global Adventures in Wireless Electronics" to my kids, Billy and Maria, noting that they were both possible future winners of this most prestigious award.  Scott Tilley's work has put us a step closer to an award ceremony for some intrepid radio amateur. 

Here is a good article on the Elser-Mathes Cup: 

http://www.arrl.org/files/file/QST/This%20Month%20in%20QST/June2016/Schoenfeld.pdf

Scott was in the news last year for finding a zombie satellite: 

https://soldersmoke.blogspot.com/2020/04/quarantine-search-for-zombie-satellite.html

A Problem with the San Jian PLJ6-LED Counter

I had hoped to use this handy and cheap little frequency counter to add some glowing Juliano Blue to the frequency readout on my Quarantine Hodgepodge rig.   I've used these boards with my BITX20, my HA-600A,  and with my DX-100/HQ-100 rigs.  But guess what -- these boards do not work with the BITX40 module board that is the heart of the Quarantine Hodgepodge.  And the reason why is interesting. 

Here is what happens:  First, you plug in the IF frequency of your rig.  In my case 12 MHz.  You connect your VFO output to the signal input on the PLJ6.  You power up the PLJ6.  You then have to select one of two IF frequency options.  One of these options ADDS your IF frequency to whatever it detects at the signal input.  In my case, for a 7.2 MHz signal it would detect a VFO signal at 4.8 MHz. If it were to ADD this signal to the IF freq,  it would readout 16.8 MHz.  And it does.  But obviously that is wrong.  So you go to the other option -- this one SUBTRACTS the designated IF frequency FROM whatever it finds at the signal input.  So here we get 4.8 - 12 =  -7.2   Almost perfect right?  But here is the problem:  The PLJ6 can't handle negative numbers!  So it displays 000000.  Not helpful. 

Here is the manual: 

https://www.mpja.com/download/35057tebasic%20manual.pdf

I didn't have this trouble with any of the other rigs because none of them required the use of negative numbers.  My BITX 20 for example had an IF of 11 MHz and has the VFO running a bit above 3 MHz -- so the PLJ6 just adds the IF to the VFO signal and Bob is my uncle.  Similar problem-free addition takes place with the other rigs. 

I found some discussion on this problem on the internet.  Here is one: 

https://groups.io/g/BITX20/topic/bitx40_and_plj_6led_frequency/4330098?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,4330098 

Some of the respondents didn't seem to understand the problem.  Others hint that the ability to handle negative numbers was as some point in the code for the PLJ6 device,  and may somehow be accessible, but no further info is provided. 

I have already worked up a possible solution, but I'm interested in how you folks would approach this problem.   Any thoughts or suggestions?  I will reveal my solution in the days ahead.   

James West, Inventor of the Electret Mic, has THE KNACK

 

James West (r) with Gerhard Sessler (l)  Bell Labs 1976

https://hackaday.com/2021/02/17/james-west-began-40-years-at-bell-labs-with-world-changing-microphone-tech/

For many reasons, this is a really nice story.  It is about a kid with The Knack, a kid who, like young James Clerk Maxwell, wanted to understand how things work.   It is also a technology story, the story of the invention of a device very important to us: the electret microphone. (Remember the earlier carbon mics in telephones?  I'll bet more than a few of our readers are guilty of stealing a few of those mics from pay phones.)  And it is a reminder of the benefits of helping kids who might need a mentor... or and Elmer.    

Thanks Hack-A-Day.  And three cheers for James West. 

Phasors and the Propeller Analogy from Walla Walla University

We covered this excellent and very illuminating work before. As a follow-up, student Konrad McClure was kind enough to send me this video, which goes the extra mile with the propeller analogy. 

For me, the most interesting aspect of this is that it provides an explanation of the phase differences between upper and lower sidebands.   I need to study more about aliasing and the Nyquist criteria.  

Check out the video.  It get us a lot closer the an intuitive understanding;  math often falls short in this area. 

Thanks Konrad! 

See also: https://soldersmoke.blogspot.com/2020/09/mixer-insights-using-propellers-and.html

Please send feedback to Konrad via the comment box below. 

Put this Chart on the Wall Above Your Workbench

 

If you are like me and sometimes forget if R=E^2/P or E^2P, this chart will help. Very useful.  

My Current Rig: The Quarantine Hodgepodge

 

As I continue to Stay In The Shack,  last week I was looking for something to do. This is what I came up with.   

Left to right: 

-- Speaker

-- Ramsey-kit QAMP20 modified for 40. I now have two MTP3055V MOSFETS in there.  

-- BITX40 Module with a solidified VFO from a Galaxy V (note the knob from a Drake 2B!)

-- Power supply 

It puts out about 15 watts SSB.  I was bracing for attacks from the 40 meter waterfall police, but no, everyone said it sounds great.  I had four very nice contacts yesterday.  It was fun. 

Still to do:  Possibly a San Jian frequency counter to give some Juliano Blue glowing numerals for the frequency readout.  This would be a step up from the Juliano Blue sticky note and  corresponding piece of black electrical tape that currently serves as the frequency indicator. 

Jean Shepherd Works Through a Satellite in a School

Ah,  1975.  Obviously a very different time...  I'm not sure if Shep would fit in well in the classrooms of today.  There was bit of Rodney Dangerfield in his demeanor -- that would likely cause some trouble.

 

But this clip was fun.  Shep was right on target when he talked about how getting your ham license used to mean that you'd "mastered a technical art." 

The OSCAR satellite they were using was 2 meters up and 10 meters down.  There was a Heathkit HF transceiver with a transverter.  And a Simpson multimeter.  That mic was a Turner +3 

Thanks to Steven Walters for alerting us to this.  

EXCELSIOR!   

Use Only Telefunken Tubes -- They Are the BEST!

No translation required.   

A Lifetime of Workshops

 

https://microship.com/consoles/?fbclid=IwAR37yc-NfOrUC93C8QZYXZfakGLf-4eBtPw2php0CpzGHBW3-fb55ciyp0w

It has been more than decade, but we've posted about Steven K. Roberts N4RVE before: 

https://soldersmoke.blogspot.com/2009/09/i-didnt-care-i-had-secret-life.html

https://soldersmoke.blogspot.com/2009/09/knack-on-bike-steve-roberts-video.html

This morning I came across his recent article about the workshops he's had over the course of his life.  Very nice.  Man, I should have held on to that SP-600 I once had.  You folks will like this: 

https://microship.com/consoles/?fbclid=IwAR37yc-NfOrUC93C8QZYXZfakGLf-4eBtPw2php0CpzGHBW3-fb55ciyp0w

Microphone Men -- A Really Nice Video

Thanks to Rogier PA1ZZ for sending me this really nice video.  

Meet Your New Soviet Neighbor -- With Hallicrafters

 

Thanks to Jeff Murray for alerting us to this.  It is obviously from World War II.   If the new neighbors had S-38s, well, that might help explain why things didn't go so well.  

A Quantum Mechanics-based Receiver. The Rydberg Detector

 

Looks like you SDR guys are going to have to up your game!  

https://phys.org/news/2021-02-quantum-entire-radio-frequency-spectrum.html?fbclid=IwAR1nZZikA9VwMYbVCSMfeoJs7cj6XVKWa49LPCQ1LfWOON-iN62LvU6k2WM

A Really Nice Video about a Regen Receiver

Thanks to Stephen Walters for posting the link to this video on the SolderSmoke Facebook page. 

I really liked the way this project was described.  I think this is the work of Ciprian in Romania. 

https://www.instagram.com/dx_explorer/

https://www.youtube.com/channel/UCgaWKPt1P-4D6YI-Opd15_Q

Really nice.   Thanks!   73  

Some Thoughts on Singly Balanced Mixers with Two Diodes and One Transformer

In 2001, out it in the Azores, I built a 17 meter version of Doug DeMaw's Double Sideband transmitter ("Go QRP with Double Sideband" CQ Magazine, February 1997).  I struggled to understand the balanced modulator -- how it mixed, balanced, and how it produced DSB.  I later presented my understanding of the circuit in my book "SolderSmoke -- Global Adventures in Wireless Electronics" pages 132-137.   In essence, I figured out that you had to think of the balancing and the mixing as two separate operations: The transformer provided the balance that eliminated the carrier (the LO signal) while the diodes presented the two signals (audio from the mic amp and LO from the VFO) with a highly non-linear path.  The LO was successively turning on both diodes then turning off both diodes. The audio signal was being "chopped" at the rate of the LO.  This produced a complex waveform that contained sum and difference frequencies -- the upper and lower sidebands.  The carrier was balanced out by the transformer because the two outputs of the transformer were always of opposite polarity, and they were joined together at the output of the mixer.    

Fast forward to 2013.  I built a 17 meter version of Farhan's famous BITX 20 rig.  Above you can see the balanced modulator stage, which also serves as the product detector. As you can see, it is essentially the same circuit as the one used by Doug DeMaw in his DSB rig. 

In 2018 I built a simple direct conversion receiver for my nephew.  For the mixer I used what I considered to be just a cut-down  version of the circuit used by DeMaw and Farhan.  I got the idea for this from Olivier F5LVG and his RX-20 receiver from SPRAT.    It had the RF signal coming in on L1 and the VFO signal coming in to the wiper of the 1 k pot.  But with this arrangement, the diodes were NOT both being turned off on half the VFO cycle, then both being turned on during the other half.  Instead, as the VFO signal swung positive, D2 would conduct and D1 would shut down.  When the VFO signal swung negative,  D1 would conduct and D2 would shut down.  It worked, but the diodes were being switched in a very different way than they had been in the DeMaw and Farhan circuits.  If you have the strong LO signal going in on L1, BOTH diodes conduct, then BOTH don't conduct.  But if you have the LO going in through the pot, one diode conducts while the other does not conduct. 

After I concluded that the BJT product detector circuit in the HA-600A was causing distorted SSB and CW reception, I tried the old DeMaw/Farhan circuit, this time in product detector mode.  See above. This worked better, but I realized that this configuration was balancing out the BFO signal, and not the IF signal.  My problem with the original product detector had been that IF signal was getting simultaneous envelope detection AND product detection.  So I decided to just switch the inputs and put the IF signal into L1 (where it would be balanced) and the BFO into  R1/R2 (the 100 ohm pot). 

This seemed like it would reduce the envelope detection problem, right?  I mean, L1 is the balanced input, right?  But I wonder if we need to consider how the diodes were being switched in this arrangement.  Instead of having both conducting and then both not conducting, in this arrangement one would be conducting during half the BFO's cycle, while the other was not.  That means that at any given moment, the two output sides of the transformer would be looking into very different loads -- hardly a condition conducive to balance. But I used LTSpice to look at the audio output under the two different port arrangements.  Sherwood advised looking at the output of the product detector with the BFO turned off --there should be no output with the BFO off.  And indeed, putting the IF signal into L1 and the BFO into the R1/R2 pot resulted in less of the distortion causing envelope detection.  The way the diodes were being switched didn't seem to adversely affect the balancing out of the IF signal.  I am not sure why this doesn't seem to cause trouble. 

There was, however, another problem with the use of this circuit in the Lafayette HA-600A:  port isolation.  The BFO signal was getting back into the IF signal input on L1.   I could see it on the S-meter.  This was worrisome not only because of the S-meter, but also because the same circuit was driving the receiver's AGC -- in effect, the BFO was turning the gain down.  Theoretically, this should not have been happening.  Look at the transformer.  the BFO currents going through L2 and L3 should be of opposite polarities and should be cancelling each other out in L1.  But obviously this was not happening.  Perhaps this was the result of the sequential way the diode are switching in this arrangement.   On the bench, if I put the BFO into L1, I saw very little BFO signal at the R1/R2 junction. If I put the BFO signal into the R1/R2 junction, I was a lot of BFO signal at the top of L1.  And that is what I saw on my S-meter when this circuit was used in the HA-600A. 

On the bench,  if I turned off the BFO and put an AM modulated signal into the junction of R1/R2, I can see audio getting through once the input signal reaches 1 volt peak.  I do NOT see that kind of "breakthrough" envelope detection when (with the BFO off) I put a modulated signal into L1.  So the singly balanced circuit is doing that it is supposed to do -- it is balancing out the the signal going into L1. 

So it seemed that with the singly balanced circuit I would have to choose: suffer from the poor port isolation or AM breakthrough.   Clearly it was time to go for a doubly balanced circuit.  And that is what I did. 

Finally, I took a look at another two diode detector, the Polyakov or "subharmonic" detector. This is a really interesting circuit that can teach us a lot about how mixers work.  Here you can run the local oscillator at 1/2 the signal frequency.  With two diodes back to back, the incoming signal is being sampled TWICE during each cycle of the local oscillator.  That is equivalent to having the signal sampled at twice the local oscillator frequency.   This circuit allows you to run the oscillator at a much lower frequency -- this could allow much greater oscillator stability.  In the circuit above, with both diodes connected, a 7 MHz incoming signal would produce a 2 kHz tone. 

Another big plus of this circuit comes if you take D1 out of the circuit (as shown).  In this configuration the circuit becomes a normal diode detector.  Here it will receive a signal at 3.5 MHz, converting that signal into a 1 kHz audio tone.  So you can get a direct conversion receiver for 40 and 80 meters fairly easily. 

Shuji Nakamura -- The Inventor of Juliano Blue LEDs

He is the 2014 winner of the Nobel Prize for Physics.   He is the person who figured out how to make blue light LEDs through the use of an Indium Gallium Nitride semiconductor.  I was reading about him this morning in "Conquering the Electron" by Derek Cheung and Eric Brach.  Thanks to Nakamura, the numerals on all my frequency displays glow in a pleasing Juliano blue.  Three cheers for Nakamura! 

More on him here: 

https://www.trumpf.com/en_US/presse/online-magazine/nobel-price-winner-nakamura-wants-more-light/