Podcasting since 2005! Listen to Latest SolderSmoke

Friday, December 31, 2021

Troubleshooting Apollo: 23 MHz Crystals in a NASA Ground Receiver


More amazing Apollo stuff from CuriousMarc. 

Here we see them struggling to find the proper frequency for one of the oscillators in a dual conversion UHF receiver from the Apollo program.  For the VCO, they needed a crystal in the 23 MHz range. They faced the same questions we face:   Series or parallel?  Load capacitance?  Fundamental or overtone? 

It just so happens that at this moment I have on my bench the 17 meter SSB transmitter that I built some 20 years ago.  And the VXO in it uses crystals in the 23 MHz range.  TRGHS. (More on the spur problem with this rig soon.  The solution does involve the 23 MHz VXO.) 

Very cool that CuriousMarc found a manufacturer still willing to produce custom-made crystals. JAN flashbacks!  LapTech Precision in Canada: https://www.laptech.com/index.php

The video above is Episode 8 in the Apollo Comms series.  If you go back one episode, you can watch Marc and his assistant troubleshoot the NASA Apollo UHF receiver.   They use very familiar troubleshooting techniques.  This reminded me a lot of what we do with older, potentially modified gear.  They were able to figure out what was wrong and  how a mod had changed things.  This set the stage for the crystal replacement selection we see in Episode 8.   Here is Episode 7: https://www.youtube.com/watch?v=87qA41A_Ies

Note:  The frequencies in this Apollo receiver were listed in Megacycles, not Mega Hertz. 

Thanks to Bob Scott KD4EBM for alerting us to this. 

Thursday, December 30, 2021

McCoy SSB Crystal Filters (1963) -- But Apparently NOT the Real (Lew) McCoy

 
Last month we were talking about this company.  Someone thought it was run by Lew McCoy of ARRL Homebrew fame, but it now appears that our Lew McCoy was not involved in the company. 

Note how they provide TWO carrier oscillator/BFO crystals for each 9 MHz filter, one for USB, the other for LSB. 

They were pricey too:  In 2021 dollars, that Golden Guardian would cost $390. 

Thanks to the K9YA Telegraph for posting the ad. 

Wednesday, December 29, 2021

My Kind of Chip: A Homebrew Discrete 555 Timer Built on Wooden Boards (video)


This is really beautiful. Radraksha Vegad (Pargrahi) from India built a discrete component version of the venerable 555 timer chip.  He built it on wooden blocks.  This leads to the kind of understanding that even Jean Shepherd would have admired.  No longer is the 555 a little mysterious black box.  No, Pargrahi shows us how it works.   

 I know we could do something similar with the NE602 or the LM386.  But probably not with an Arduino microcontroller or an Si5351.  And that says something about understanding and complexity. 

Thanks Radraksha.  And thanks to Hack-A-Day for alerting us to this: https://hackaday.com/2021/12/20/all-hail-your-new-giant-555-timer-overlord/#more-512230 


Tuesday, December 28, 2021

How to Fix the Spur Problem in my 17 Meter SSB Transmitter?

 

I built the transmitter almost 20 years ago.  It is in the larger box, which originally housed a Heathkit DX-40.  There is a lot of soul in that old machine.  Details on this construction project are here: https://soldersmoke.blogspot.com/2021/12/junk-box-sideband-from-azores-2004-qst.html  (The smaller box is a Barebones Superhet receiver set up for 17 meters.) 

In the 2004 QST article I discuss a problem I had with "spotting" or "netting."  This is something of a lost art, something that you had to do back in the pre-transceiver days, when running a separate transmitter and receiver.  This was how you got the transmitter on the receiver's frequency.  Essentially you would turn on the carrier oscillator and the VFO and let a little signal get out, enough to allow you to tune the VFO until you heard zero beat on the receiver.  My problem was that around one particular frequency, I would hear several zero-beats.  This made netting the receiver and the transmitter hard to do.  

Important note:  This is really just a problem with the "netting" or "spotting" procedure -- the problematic spur does not show up in any significant way in the output of the transmitter.  I can't see it on my TinySA.  But it is strong enough to be heard in the unmuted receiver sitting right next to the transmitter. And that creates the netting problem. 

In the QST article, I said that I noticed that the problem seemed to be centered around 18.116 MHz.  As I approached this frequency, the tones -- desired and unwanted -- seemed to converge. That was an important clue.  In the article I said I thought that I could eliminate the problem with just one trimmer cap to ground in the carrier oscillator, but looking back I don't think that this really fixed the problem. 

I recently took a fresh look at it.  Exactly which frequencies were causing the unwanted signals that appeared in my receiver? 

I used an Excel Spread sheet to find the culprits. 


The first column shows the carrier oscillator and its harmonics.  The second column shows the VFO when tuned for a signal at 18.11668 MHz (23.2927-5.17602), along with its harmonics.  Check out the 10th harmonic of the carrier oscillator and the third harmonic of the VFO: 69.8781-51.7602 = 18.1179.   Those two harmonics would produce the problem I had been experiencing. 

I turned to one of Wes Hayward's programs for confirmation.  Spurtune08 came in the EMRFD software package. Here is what I saw when I plugged in the above frequencies:    


You can see the little spur off to the left of the main signal.  In the program, as I tune the 23 MHz VFO frequency, the spur moves closer to the main frequency as I approach 18.116 MHz, just as it does in the real rig.   Note that I have only turned on the 10th harmonic of the carrier oscillator and the 3rd harmonic of the VFO.  Spurtune08 is very useful.  Thanks Wes! 

So, what is to be done?   For now, I am just restricting my operations on 17 meters to above 18.120 MHz.  (I worked several DX stations with it on December 27.)  But obviously I need to fix this. This rig needs an exorcism.  I think I only need to get rid of one of the harmonics, and the 10th harmonic of  the carrier oscillator seems easier to kill.  I'm thinking of putting the carrier oscillator in an Altoids box, and then adding some filters to knock down the 10th harmonic. 

Here is the G3YCC schematic that inspired this rig.  I used G3YCC's carrier oscillator and balanced modulator circuits, just using a 5.176 MHz crystal and changing the tank circuit in the collector: 


How would you folks knock down that 10th harmonic? 

Monday, December 27, 2021

A Christmas Story: Mike AA1TJ Builds Receiver for 486 kHz, Listens to Fessenden Commemoration (Audio)

Mike's 486 kHz receiver

As if being able to get home on Christmas Eve 2021 and then catching the Webb Telescope launch was not enough, Santa had another gift for us:  Michael Rainey, AA1TJ, the Homebrew Hero of the Hobbit Hole, was back at it, melting solder. Mike threw together a regen receiver that allowed him to receive a transmission commemorating Reginald Fessenden's historic first transmission of phone signals.  I was really pleased to once again be able to read about an AA1TJ radio adventure.  Thanks Mike!  Here is what Mike heard: http://soldersmoke.com/AA1TJ 920km.mp3

Mike wrote: 

My chum, Peter/DL3PB, recently told me that Brian/WA1ZMS would broadcast a commemoration of Reginald Fessenden's mythical (operative word) 1906 Christmas Eve AM transmission. Doesn't that sound like fun?

True to form, I began scratch-assembling my receiver yesterday afternoon just as Brian went on the air. Then again, a two-transistor regenerative radio for 486kHz isn't exactly rocket science. In any case, I was up and listening inside of a half hour.
 
What did I hear? Static. Just static. As a sanity test I quickly tuned down to 371KHz to find my favorite non-directional beacon, "GW," beaming in loud and clear from Kuujjuarakip.
 
Kuujjuarakip?

Kuujjuarakip is a tiny settlement of mostly Inuit and Cree inhabitants located up on Hudson Bay. The villages are primarily accessible by air and water so a robust radio beacon is an obvious necessity.
 
Satisfied that my receiver was working properly, I re-tuned to 486kHz. Back to static. On the bright side, at least there were no commercials. I continued listening intently until Vic called me to dinner. After the dishes were done I slipped back down to my underground radio shack for one last try.

I heard it right away. Beneath the static I heard a weak, out-of-tune, solo violin playing, "Oh, Holy Night." The signal strength varied wildly with ionospheric propagation. When the signal finally climbed high enough above the noise I ripped out the bipolar transistor audio amplifier stage, connecting my headphones directly to the junction field effect transistor detector output terminals. Of course the audio was far weaker now, yet I could easily follow the tune until it eventually faded away. Not bad for an estimated 15 watt ERP AM signal from a distance of 920km. And on 486kHz, no less, just a hop-skip-and a jump from the old 500kHz Maritime CW band; where countless ship radio operators went to send their last SOS.
 
Returning to the house, I emailed my reception report and included a short recording that I had made of it. Brian replied just after midnight; apparently, equally as stoked

"Yours’ is the best DX ever given your regen RX! Way to go! I just love it."

He went on to tell me that he was born and raised in Vermont, but he'd been working as a radio scientist down in Virginia since 1990. Told me his heart was still here in the Green Mountains and he was touched to learn his meager signal had found its way back there on Christmas Eve. All in all, a night to remember.
 
If you're still with me I hope you'll listen to the short NPR story in the provided link. It originally aired on the supposed 100th anniversary of this event. It's not just about radio history. It's about belief, memory and the myths we lug around in our heads. I thought it was well done.
 
Cheers,
Mike

Listen to what Mike heard. He says he "merely connected the mic input line of my computer across the headphone terminals. Some of the noise in the recording, - certainly the higher frequency stuff - is a byproduct of the computer. The headphone audio with the computer switched off was much more pleasant."  Here it is: http://soldersmoke.com/AA1TJ 920km.mp3

NPR story (audio and text)

Saturday, December 25, 2021

A Nice Christmas Gift Out of French Guiana -- The Launch of the James Webb Space Telescope

 
A nice Christmas present from NASA and ESA on the screen early on Christmas morning.  

Track Webb Telescope's progress here: 

The (Real) Solar Flare of August 1972 in Cixin Liu's Science Fiction

 

A view of McMath Region 11976 from the Paris Observatory early on 4 August 1972. 

I have a vivid memory of seeing -- as a kid -- Aurora from our home near New York City.  Eric Carlsen, my childhood friend and colleague from the Waters Edge Rocket Research Society,  told me his mom had similar memories. A while back I did some Googling and concluded that it had to have been the monster solar flare of  August 1972:

 https://soldersmoke.blogspot.com/2009/09/carrington-flares-aurora-where-were-you.html    

That blog post got about eight comments, mostly from other folks with similar memories -- they apparently were led to my blog by the same kind of memory-based Googling that I had done. 

This year, on Christmas Eve, Elisa and I were flying home from the Dominican Republic. I was reading (on my phone) "To Hold Up the Sky," an anthology of Cixin Liu's science fiction short-stories.   I'd read his excellent "Three body Problem" in the Dominican Republic back in December 2017.   His work is usually "hard" sic-fi, with a strong connection to real physics.

One of the short stories in the anthology is entitled "Full Spectrum Barrage Jamming." Wow, I thought, that one is really promises to be very interesting for a radio amateur.  I turned out that it was more interesting than I expected. 

I won't spoil the story for you.  Suffice it to say that Cixin Liu makes reference to the same August 1972 solar flare that I remember from my childhood, and discusses its effect on radio propagation.  It was really kind of eerie to be in that plane, flying over the Bahamas, reading Chi-Fi on my I-phone, and seeing the author reference that memorable event from 1972.  TRGHS. 

There were plans to turn this story into a movie: https://www.yicaiglobal.com/news/wandering-earth-producer-to-film-another-liu-cixin-novel

Here is an excellent article describing what happened back in 1972: https://room.eu.com/article/lessons-from-the-sun.   The August 1972 flare was so strong that it caused U.S. Navy anti-ship mines to explode in Haiphong harbor in Vietnam. 

Saturday, December 18, 2021

On 17 meter CW from Santo Domingo with a uBITX



We are up on the 12th floor of a building in Santo Domingo. I brought my uBITX and managed to check in as baggage a 16-foot crappie fishing pole. I figured I needed to get the 1/2 wave antenna away from the building -- last time I was here I was unable to make any contacts from this location with the antenna stretched along the balcony. Last time I was QRP with an SST transceiver. 

The fishing pole worked well, but I operated with fear that it would fall or that the neighbors would complain). Today I got on 17 CW with the uBITX (more power than the SST), put it on 17 CW and promptly worked W4A, a special events station commemorating E. Howard Armstrong.  Turns out that today is Armstrong's birthday.  TRGHS.  

On the Reverse Beacon Network my CQs were heard by KO7SS in Arizona (very cool skimmer station at 8100 feet!) and by W2NAF (interesting operations in Antarctica, Svalbard and Virginia Tech). 



Sunday, December 12, 2021

Hack-a-Day: Has DIY become Click-and-Buy?

https://hackaday.com/2021/12/11/has-diy-become-click-and-buy/


Hack-A-Day today asks about the boundaries between DIY construction and the use of purchased, completed electronic components.   This is closely related to our long-standing discussion of what really constitutes "homebrew." 

Is it really homebrew if you buy a bunch of  already-stuffed PC boards and connect them together?  

Is it really a homebrew receiver if 90% of the components are inside one chip? 

Is it really homebrew if most of the signal processing is done in your computer (that you definitely did not build)? 

The comments below the article are interesting.  There we see some of the same arguments used by ham radio operators who are more inclined toward click-and-buy. They argue that since none of us are making our own resistors and transistors, we are ALL therefore click-and-buy people, so we should just get over it and pull out the credit cards. Some commenters carry this to extremes and ask if the real homebrewers are out there mining the copper for their wires.  

The debate seems to spill over into the software area:  One person asks if it is really DIY if you are using software libraries that contain code written by someone else.  Or to be truly DIY should you write all of your own code in assembly language?    

There is one very insightful comment about hams who are inclined to disparage the homebrewing that they did in their youth.  We often hear this:  "Oh, I used to build my own gear, but now-a-days I just buy commercial transceivers -- they are so much better."  As if homebrewing was a folly of youth, something that they grew out of (and up from) as they became able to afford the latest ham radio appliances.  As if homebreweing were a regrettable thing that was done only out of necessity.   This is, I think, sad.  

I think I'm a lot closer to the traditional concept of DIY than I am to click-and-buy.  I still prefer LC oscillators to Si5351/Arduino combos.  I prefer traditional filter rigs to SDR rigs.  And I prefer to make my own crystal filters.  I don't like to use ICs unless I really understand what is going on inside them (so I can be comfortable with an NE602 or an LM386, but I'm not comfortable with a CPU chip that may have millions of transistors in it).  But I am not homebrewing my own transistors nor am I mining copper. 

What do you folks think about this? 

Friday, December 10, 2021

The Lamakaan Annual Radio Convention Starts Today!

 


The Lamakaan Amateur Radio Club's annual convention begins today in Hyderabad, India.  This is Farhan's club so it is sure to be a great event.  Presentations are being live streamed on YouTube and on the QO100 geostationary satellite. 

Here is the link to the convention: http://www.larc.in/larc4/

Pete N6QW will be the first presenter and will talk about his new PSSST Rig. He will be speaking at 0430 UTC Saturday 11 December.  That is 11:30 pm on Friday, December 10 on the East Coast of North America.  

I will be speaking at 1130 UTC on Sunday December 12.  That is 0630 Saturday 11 December EST. I'll be talking about the Mythbuster rig and about the ET-2. 

Here is the schedule.  




Here's a time zone converter: https://www.timeanddate.com/worldclock/converter.html?iso=20211211T043000&p1=505&p2=250&p3=137

Here is the Lamakaan Club's YouTube Live Channel.  https://www.youtube.com/watch?v=cRznKwGgvDo

I don't know how we might be able to watch or listen via the QO100 satellite.  The U.S. is not in the footprint of this bird.  But there is a good WEBSDR receiver run by BATC and AMSAT DL: https://eshail.batc.org.uk/

Where is Sunspot Cycle 25?


The other day I was complaining to Pete N6QW that 17 meters still seems to be in very poor shape.  I can hear 6Y6Y around mid day, but I don't often hear Europeans.  I did year my friend Mike EI0CL yesterday on 17, but conditions were not good.  Pete asked, "Where is Cycle 25?"  Good question. The Space Weather Center has the answer.  

Their Solar Cycle Progression page is up-to-date.  With the slider below each chart you can go back as far as 1750.  Check out Cycle 19.  I was born near the peak (TRGHS).  Pete was on the air during that cycle. Cycle 23 also looked pretty good. I was out in the Azores then (2000-2003) -- no wonder I could work VK and ZL with a 5 watt DSB rig.  

I like the little solar conditions widget that has appeared in the left hand column of this page, and I am grateful to the provider,  but the widget just doesn't update regularly.  So I think I'm going to switch to a link from the Space Weather Prediction Center that shows the numbers we really need: Solar Flux Index (SFI), Sunspot Number (SN), A index, K index.  (Please let me know what you think about this change.) 

Here is the link to the Solar Cycle Progression Charts (be sure to use the sliders):  

https://www.swpc.noaa.gov/products/solar-cycle-progression

Thursday, December 9, 2021

Bluetooth, Winston Churchill, The Speed of Light, and a 1938 Zenith Receiver

 

Hello Bill -


It has taken me a while to put hands on keyboard to send you this message, but having seen or heard a few more of your references to Jean Shepherd, I felt I must. Being a fan of vintage radio equipment and the American scene of the late 1930s, sometime back I acquired a very nice circa 1938 Zenith 5-S-119 AM/Shortwave radio. 


Though it had been recently re-capped, it took some effort to get the thing working (needed a new power transformer), and still needs to be aligned, but it made a nice addition to my 1930s NYC Art Deco-inspired office. One reason I bought it was to add a Bluetooth receiver to it so I could listen to podcasts, etc, from my phone. I like the big electromagnetic speaker that those radios have and thought it would be cool to bring this one back to life. I picked up a small Bluetooth receiver board and a power supply for a few dollars online and got it working in the Zenith with no difficulty, except for some AC hum and oscillator noise that I will work on when I have time. So, success!

But here is the Jean Shepherd part. I recall one of his broadcasts in which he offered his theory that every radio transmission ever made is still out there, traveling further and further into intergalactic space and getting weaker and weaker, but still there. What an idea that was. I would say he is right. I have pondered the idea ever since. So being also a Winston Churchill fan, what would be the first recording I would play through the Bluetooth? What else but his 1940 blood, toil, tears, and sweat speech! So there was the scene — the Churchill speech playing the same audio waveform through a radio that might very well have played it live (or close to live) back in 1940! Almost (though not quite) like detecting the original still-traveling radio signal out there past the star Phi2 Ceti or wherever it is now!

Well that was a quick adventure this past summer that I thought you might appreciate.

Keep the Solder Smoke podcasts coming!

Tom Fuhrman, WX2J

Wednesday, December 8, 2021

Barrie Gilbert and Tinkering, Surplus, and the Visceral Experience of Electronics

 

Barrie Gilbert, 1951

From https://www.edn.com/analog-back-to-the-future-part-two/  :

"Gilbert believes that childhood hardships—including at age three losing his father in World War II, leaving his mother and three other children penniless—force one to be resourceful. Before and during his teenage years, he had access to a plethora of inexpensive military surplus gear which greatly helped to make him inventive. Gilbert laments that today's aspiring engineers are lacking the visceral experience of handling and hefting large coils and tuning capacitors, transformers and vacuum tubes, and such. Today’s surplus circuit boards are all but useless as a source of inspiration, or even “spare parts” to tinker with."

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

A really wonderful autobiography by Barrie Gilbert starts on page 7 of this page: https://hephaestusaudio.com/media/2009/06/the-gears-of-genius.pdf 

Tuesday, December 7, 2021

Junk Box Sideband from the Azores (2004 QST Article)


About 20 years after I first built it, I find myself working on and using this SSB transmitter.    I recently added some impedance matching to the Swan 240 crystal filter;  several years ago I replaced the PA with a "JBOT" amplifier designed by Farhan VU2ESE.  I now have it on the air, using it with a highly modified Doug DeMaw, Barebones "Barbados" superhet  receiver. I had my first (recent!) QSO with this station yesterday, with Les 6Y6Y on the beach in Negril, Jamaica. 

More on this project in due course. Lots of soul in this machine. 

I'd forgotten about this article -- thanks to Pete Eaton for reminding me. Click on the images for a better look at the article. For an even clearer view, download the images and then open them on your computer. 


Monday, December 6, 2021

Early Radio in New Zealand, and "The Knack"

 

Thanks to Thomas K4SWL of the SWLing Post for alerting us to this gem.  Listen to Sarah Johnston's program describing the origins and early years of broadcast radio in New Zealand. 


This wonderful recording and article reminded me of a bit of ham radio history involving New Zealand,  and someone who was involved who had a surname similar to mine.  The ARRL book "200 Meters and Down" by Clinton DeSoto reports on page 91 that on May 22, 1924, radio amateurs for the first time made a contact between New Zealand and South America.  Carlos Braggio operated rCB8 in Buenos Aires.  In New Zealand, J.H. O'Meara was at the key in Gisborne. 

Writing of the early amateurs,  DeSoto wrote (on page 92): 

 "Why did they do it?  None but one of them can know, and only he would know the feeling of driving ambition, the relentless call of work to be done, the gnawing discontent that hungers for accomplishment; it would be hard to put into words. The strange thing is that there were folk, everywhere on earth it seemed, who had that urge." 

"The gnawing discontent..."  That is what Jean Shepherd had when he couldn't get his Heising Modulator to work properly.  We've all been there. 

The last line in the quote from DeSoto's book speaks to one of the major themes of this blog and of the SolderSmoke podcast:  the way in which people all around the world got interested in radio in much the same way.  So many of us, all around the world,  often at age 13 or 14, suddenly got interested in radio.  We all had (and have!) "The Knack."  This is really very nice -- it is something that we have in common, something that pulls us together. 

Sunday, December 5, 2021

Jack NG2E's Winter SOTA Marathon in the Shenandoah

  

Our friend Jack NG2E is a homebrewer.  He is also a Summits-On-The-Air guy. He does much of his SOTA operations along Skyline Drive in the Shenandoah National Park. Jack's Story Map method of documenting this SOTA trip is very cool. 

Elisa and I are frequent visitors to this amazing park.   Both my kids went to college in the Shenandoah valley, and the park starts just one hour by car west of us.  It is a beautiful place. The Appalachian Trail runs through the park;  we have crossed paths with "through hikers" who are walking from Maine to Georgia. We have also met up with more than one Black Bear in the park (see below).  My son Billy and I launched our Green Hornet rocket from a farm in the Shenandoah valley: https://soldersmoke.blogspot.com/2017/05/still-photos-and-slow-motion-video-from.html

I really like Jack's use of both HF and 2 meter FM.  This makes me think that I should blow the dust off my Baofeng HT and bring it out to the Shenandoah next time we visit.  Jack's 20 meter CW contact with Christian F4WBN in the Pyrenees added a nice element of transatlantic mountain symmetry.  

Check out Jack's Shenandoah Story Map: 

https://storymaps.arcgis.com/stories/c9ff4a13eca24b37bc9dcda0d2dce989

Here's another story map from a SOTA trip into the Adirondacks with info on his gear: 

https://storymaps.arcgis.com/stories/594ca069a27147c1a8d8b79dc1513a72

I know that Jack wants to include a homebrew rig in his SOTA operations.  That would significantly add to the already very high level of operational coolness.  Perhaps Colin M1BUU or Paul VK3HN could provide some suggestions or encouragement in this area. 

Thanks Jack.  Happy trails. Regards to the bears!  

Saturday, December 4, 2021

Dean's Supercharged, 16-Watt, Furlough 2040, Simple SSB Rig

 

'Tis a thing of beauty. 

It is especially appropriate for us to use that Irish phrase because the design of the rig's new final amplifier is out of  Ireland. Our friend Dean KK4DAS added a 16 watt RF amplifier based on a design by EI9GQ to his homebrew N6QW Simple SSB rig.  Note the IBEW label on the top. 

Here is Dean's blog post on this wonderful project (with video and more pictures). 

Dean has it on the air and is getting good reports.  He has clearly come a LONG way from his Michigan Mighty Mite build of just two years ago.  FB OM. 

Here is Dean's build of the EI9GQ 16 Watt Final

Final final assembly! 


A Great Morning on the Old Military Radio Net: AB9MQ's Central Electronics 20A, W3EMD's Dynamotor, WU2D

Just a portion of Masa's shack

I usually try to listen in on the Old Military Radio Net on Saturday mornings (3885 kc).  Lately I listen with my Mate for the Mighty Midget receiver.  

This morning's session was especially good.  For me the highlight was when Masa AB9MQ called in from Normal, Illinois using his Central Electronics 20A (see below).   That was one of the earliest SSB rigs.  A phasing rig, it also ran AM (which was what Masa was using this morning).  He had it paired up with a Central Electronics 458 VFO.  You folks really need to check out Masa's QRZ.com page: 

https://www.qrz.com/db/AB9MQ

Buzz W3EMD called in from Rhinebeck, NY.  I could hear his dynamotor in the background.  Buzz said hello to Masa in Japanese.   FB.

Always great to hear Mike WU2D


Friday, December 3, 2021

Alan Wolke W2AEW: YouTube Silver Play Button Award, and ARRL Hudson Division 2020 Technical Achievement Award

Three cheers for Alan Wolke W2AEW, truly one of the great guys of homebrew ham radio.  Alan's wonderful YouTube videos have enlightened hams all around the world.  He is always there to answer questions and help hams (like me) who are at times struggling to understand technical concepts. 

Photo from the November 13, 2021 ARRL Hudson Division Awards Luncheon. That’s Alan with the ARRL CEO David Minster NA2AA, the Nobel Prize winning Dr. Joe Taylor K1JT, and 2021 Technical Achievement winner David DeCoons WO2X. Alan was presented with the division’s 2020 Technical Achievement award. 

Thursday, December 2, 2021

Peter Parker VK3YE Inducted Into QRP Hall of Fame


Wow, I was really pleased to learn that Peter Parker VK3YE was a 2021 inductee into the QRP Hall of Fame.  

This is a richly deserved honor.   Peter Parker  has been making extraordinary contributions to QRP and homebrewing for many years.  I remember reaching out to him when I was just getting started with homebrew phone gear.  I considered him a guru of DSB.  He helped me a lot.  Peter Parker was interviewed on the SolderSmoke podcast in 2013: 

Peter has published many books and has produced many YouTube videos.  He hosts an annual QRP gathering in his beloved home-town of Melbourne Australia that gets attention from solder-melters around the world.  

Three cheers for Peter Parker!  

Congratulations Peter! 

VK3YE's Web Site: https://vk3ye.com/

VK3YE's QRZ.com page:   https://www.qrz.com/db/VK3YE 

Thanks to VK3HN for alerting me to this. 

Wednesday, December 1, 2021

KI4IO in India and Nepal, and Discrete Homebrew Gilbert Cells


Jerry KI4IO is such an amazing homebrewer that he has been dubbed "The Wizard of Warrenton." The picture above shows Jerry during the early 1980s in the shack of Father Moran 9N1MM in Nepal. Jerry was also in India.  (I previously posted the info on Jerry's time in India and Nepal, but I didn't have this picture.  The picture makes it worthwhile to post the story again.)  From Jerry's QRZ.com page: 
-------------------------------

While in India I was licensed at VU2LHO and worked a lot of US hams with a 135' flat-top and open-wire feed. I had the antenna strung between two bamboo towers atop the embassy housing 2nd-story roof-top. I also put up a 3/8 wave vertical on the roof for 10 meters. That little antenna had 110 radials stapled into the roof screen and worked very well! The rig was a HW-101. I was in Kathmandu, Nepal from early 1980 to late 1982. I could not obtain a license there, but became good friends with Father Moran, 9N1MM, and would often spend time up at his place putting his Drake station on CW. Pretty cool being real DX! Back in the states in late 1982.

Here I am at one of my many visits to Father Moran's shack. 
---------------------------------
Check out Jerry's QRZ.com page: https://www.qrz.com/db/KI4IO

I got in touch with Jerry because Pete Eaton reminded me that Jerry had homebrewed a discrete transistor version of the NE602 Gilbert Cell Mixer, a device that I am very interested in. Nick G8INE also built one. 

Tuesday, November 30, 2021

Putting a Barebones Superhet on 17 Meters with an NE602 Converter (Video)


Armed now with a NanoVNA, I took a look at the passband of the 5 MHz filter in my Barebones Superhet (BBRX)  W4OP built it on a Circuit Board Specialist Board.  He put a 5 MHz CW filter in there;  I broadened the passband for phone by changing the values of the capacitors. Here is what the passband now looks like in the NanoVNA: 


This is what DeMaw would call an "LSB filter."  You would get much better opposite sideband rejection by using it with an LSB signal, placing the BFO/Carrier Oscillator slightly above the passband, in this case near 5.002 MHz. 

When I first built the down converter to get the 18.150 MHz signal down to the 7 MHz range (where I had the receiver running) I used an 11 MHz crystal for the NE602's local oscillator.  But this created a big problem:  18.150 - 11 =   7.150 MHz.  That is in the 40 meter band, but note:  NO SIDEBAND INVERSION.   Then in the BBRX  7.150 MHz - 2.150 MHz = 5 MHz  (the filter frequency) but again:  NO SIDEBAND INVERSION.   The signal started as a USB signal and remained a USB signal. 

I briefly tried shifting the BFO frequency to the other side of the filter passband.  If I could get it to around 4.985 MHz, it might work, but because the filter passband was so large, and because the crystal frequency was so low, I was unable to shift the crystal frequency that far.  In any case the results would have been less than ideal because of the "LSB" shape of the filter.  Back to the drawing board. 

I decided to cause one sideband inversion. 

At first I put a 25.175 MHz crystal module in my down converter.  This shifted the 17 meter phone band down to the 40 meter CW band.  It worked, but I cold hear strong 40 meter CW  signals being picked up by the wiring of the receiver (the box is plastic!).  I went back to the module jar in search of frequency that would move 17 meter phone to the 40 meter area (so I would not have to re-build the BBRX front end) but outside the actual 40 meter band.  

I ended up using a 25 MHz crystal in the down converter. 25 MHz - 18.150 MHz = 6.85 MHz WITH SIDEBAND INVERSION.  After checking on the NA5B Web SDR to see that there are no strong signals in the 6.835 to 6.89 MHz range, I retuned the output circuit on the converter and tweaked the input capacitor on the Barebones.  I shifted the VFO frequency down to 1.835 to 1.89 MHz and put the BFO at 5.002 MHz.   The receiver was inhaling on 17 meter SSB.  

One more change to the BBRX:  in his June 1982 QST article, DeMaw warned that trying to get speaker level audio out of the 741 op amp that he used would result in audio distortion.  And it did.  So I put one of those little LM386 boards I have been using into the BBRX box.  I just ran audio in from the wiper of the AF gain pot.  It sounds good.  

In effect this is my first double-conversion receiver.  I usually prefer single conversion, but this project has highlighted for me one of the advantages of double conversion for someone like me who eschews digital VFOs:   Starting with a crystal filter at 5 MHz,  with double conversion I could keep the frequency of the LC VFO low enough to ensure frequency stability.  That would have been impossible with a 5 MHz IF in a single conversion 17 meter rig.  But if I were starting from scratch for a 17 meter rig, I could stick with single conversion by building the filter at 20 MHz,  keeping the VFO in the manageable 2 MHz range. 

Now, on to the SSB transmitter.   The Swan 240 dual crystal lattice filter from the early 1960s needs some impedance matching. 

Sunday, November 28, 2021

How To Understand the NE-602 and the Gilbert Cell Mixer

 


I think the key to understanding the Gilbert Cell Double Balanced mixer is to separate out the three tasks that this device completes, and consider them one at a time, using different diagrams: 

1) It mixes two signals to produce sum and difference outputs. 
2) It balances out the RF input. 
3) It balances out the LO input. 

                                                                  Task 1 -- Mixing


The Gilbert cell is like the diode ring mixer in that it switches the polarity of the input signal at a rate set by the Local Oscillator. Another way of saying this is that the mixer multiplies the input signal by 1 and by -1. 

Steve Long of the University of California described the essence of this mixing this way (using the diagram above): 
 
An ideal double balanced mixer simply consists of a switch driven by the local oscillator that reverses the polarity of the RF input at the LO frequency.  http://literature.cdn.keysight.com/litweb/pdf/5989-9103EN.pdf

In an effort to see this for myself, I drew (noodled!) this diagram: 


There are four transistors -- two differential pairs with RF coming into the bases of the pairs. 
The LO is a square wave.  The LO alternately turns on transistors 1 and 4, then 2 and 3.  When 1 and 4 are on, we are in period 1 -- here there is no switching of polarity.  Portions of the RF waveform are passed to the outputs.  But when the LO turns on transistors 2 and 3, portions of the RF wave form are "crossed over" to the opposite output.  Polarity is reversed.  We see this in period number 2. 

Take a look at the resulting output waveforms.  This is the same waveform we see coming out of a diode ring mixer.  I really like this drawing because in that complex waveform you can actually see the sum and difference frequencies: 


I could see this diode ring waveform myself on my oscilloscope: 


TASK 2 -- Balancing Out the RF Input 

In a diode ring, and in other diode mixers, the balancing out of the input signals really takes place in the trifilar toroidal coils that are part of the circuit.  Barrie Gilbert needed an integrated circuit mixer that did not use coils.  


Again referring to the above diagram, Steve Long of the University of California put it this way: 

The ideal balanced structure above cancels any output at the RF input frequency since it will average to zero.

To fully understand this I find it helps to look at the Gilbert cell circuit drawn in a different way.  Here is a drawing from Alan Wolke W2AEW that I found very helpful. It comes from his excellent YouTube video: https://www.youtube.com/watch?v=7nmmb0pqTU0


Suppose the RF waveform at I1 is causing the current through R1 and R2 to increase.  At the same time, the opposite phase current through I2 will be causing the current through R1 and R2 to DECREASE.  So there is no net effect of the RF signal at the output.  The RF is balanced out. 

TASK 3 - Balancing Out the Local Oscillator Signal 


Here too I used my own drawing, and was guided by the words of Steve Long: 

It also cancels out any LO frequency component since we are taking the IF output as a differential signal and the LO shows up as common mode.  

The important thing to realize here is which transistors are being turned on and off by the local oscillator signal.  On one half cycle of the LO, transistors 1 and 4 are on.  So  the LO signal at the LO frequency are both pulling the same amount of LO frequency current through the resistors. So you have the same change in voltage at the output terminals.  And the output terminals are differential.  The LO signal results in no voltage difference between the terminals.  So the LO frequency is balanced out. 

The same thing happens on the following half of the LO cycle.  Here, transistors 2 and 3 are turned on. Again, both transistors pull the same amount of LO frequency current through the resistors. There is no differential voltage.  So no LO frequency energy passes to the output.  LO frequency is balanced out. 

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

I am surrounded by Gilbert Cell Mixers and I have been using them in my homebrew rigs for many years. I use them in up-converters for my RTL-SDR receivers.  I have one in the downconverter for my 17 meter receiver and had one as the mixer in my first SSB transmitter. I built a 40 meter SSB transceiver with NE602s on either end of the crystal filter. Years ago, I built a DSB transceiver with several NE602s.  My SST QRP CW transceiver is made with NE602s. I have on my bookshelf Rutledge's book "The Electronics of Radio" that is all about the NORCAL 40 transceiver, built using NE602 chips.  But until now I really didn't know how these chips worked.  Truth be told, for me they were mysterious little black boxes, and that bothered me.  Now I feel a lot better about using these clever devices.  I plan on stocking up on the old style (non-SMD) NE602s.  

Apparently Barrie Gilbert rejected the idea that he invented the circuit that bears his name.  It seems that Howard Jones first used this circuit in 1963, with Gilbert developing it independently (in an improved form) in 1967. 

 Barrie Gilbert was quite a guy, with electronic roots in the world of tinkering: 


Saturday, November 27, 2021

The Galway Radio Experimenters Club

 

My old friend Mike EI0CL used to remind me that hams in Ireland are granted not just an amateur radio license, but an amateur radio experimenter's license, with an emphasis on experimentation. I think we can see that emphasis in the newsletter of the club.  It has a remarkably high level of technical content.  Check it out, and look at more information on the club: 


Here is their latest newsletter: 

Pete N6QW's PSST rig is mentioned on Page 4 of the Winter 2021 edition. TRGHS. 

Thanks to John EI7GL for alerting us to this gem via his FB blog

Wednesday, November 24, 2021

Gloria -- A Netflix Series about a Shortwave Broadcast Station in Portugal


Rarely if ever will we come across a high quality NETFLIX series built around a shortwave broadcast transmitter.  But that is what we have in Gloria.    It is really good.  We were especially interested in it because we lived in Portugal for three years. In addition to all the intrigue and drama you will catch glimpses of broadcast antennas, big transmitting tubes,  and one out-of-focus shot of what appears to be a Hallicrafters receiver (SX-42?)   

More info here: 

https://www.forbes.com/sites/sheenascott/2021/11/13/gloria-netflixs-first-original-series-from-portugal-is-a-great-spy-thriller/?sh=446cef9b30d7

Here's the NETFLIX link: 

https://www.netflix.com/title/81073977

Thanks to Thomas K4SWL of SWLing Post for the heads up


Tuesday, November 23, 2021

Jagadish Chandra Bose

Jagadish Chandra Bose

(30 November 1858 – 23 November 1937)
Acharya Sir Jagadish Chandra Bose, was a Bengali polymath, physicist, biologist, botanist, archaeologist, as well as an early writer of science fiction. He pioneered the investigation of radio and microwave optics, made very significant contributions to plant science, and laid the foundations of experimental science in the Indian subcontinent. IEEE named him one of the fathers of radio science. He is also considered the father of Bengali science fiction. He also invented the crescograph.
Born in Bikrampur (present day Munshiganj District near Dhaka in Bangladesh) during the British Raj, Bose graduated from St. Xavier's College, Calcutta. He then went to the University of London to study medicine, but could not pursue studies in medicine due to health problems. Instead, he conducted his research with the Nobel Laureate Lord Rayleigh at Cambridge and returned to India. He then joined the Presidency College of University of Calcutta as a Professor of Physics. There, despite racial discrimination and a lack of funding and equipment, Bose carried on his scientific research. He made remarkable progress in his research of remote wireless signaling and was the first to use semiconductor junctions to detect radio signals. However, instead of trying to gain commercial benefit from this invention, Bose made his inventions public in order to allow others to further develop his research.
Bose subsequently made a number of pioneering discoveries in plant physiology. He used his own invention, the crescograph, to measure plant response to various stimuli, and thereby scientifically proved parallelism between animal and plant tissues. Although Bose filed for a patent for one of his inventions due to peer pressure, his reluctance to any form of patenting was well known. To facilitate his research, he constructed automatic recorders capable of registering extremely slight movements; these instruments produced some striking results, such as Bose's demonstration of an apparent power of feeling in plants, exemplified by the quivering of injured plants. His books include Response in the Living and Non-Living (1902) and The Nervous Mechanism of Plants (1926).
......Bose's education started in a vernacular school, because his father believed that one must know one's own mother tongue before beginning English, and that one should know also one's own people.
Speaking at the Bikrampur Conference in 1915, Bose said:
“At that time, sending children to English schools was an aristocratic status symbol. In the vernacular school, to which I was sent, the son of the Muslim attendant of my father sat on my right side, and the son of a fisherman sat on my left. They were my playmates. I listened spellbound to their stories of birds, animals and aquatic creatures. Perhaps these stories created in my mind a keen interest in investigating the workings of Nature. When I returned home from school accompanied by my school fellows, my mother welcomed and fed all of us without discrimination. Although she was an orthodox old-fashioned lady, she never considered herself guilty of impiety by treating these ‘untouchables’ as her own children. It was because of my childhood friendship with them that I could never feel that there were ‘creatures’ who might be labelled ‘low-caste’. I never realised that there existed a ‘problem’ common to the two communities, Hindus and Muslims.”

Thanks to K.P.S. Kang for alerting us to this.

More on J.C. Bose here:

And here are some really interesting notes from NRAO sent to us by Drew N7DA:

There is a crater on the Moon named for him.
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column