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Showing posts with label Souleles -- Dean. Show all posts
Showing posts with label Souleles -- Dean. Show all posts

Saturday, February 17, 2024

Nate KA1MUQ's Amazing Thermatron Receiver



Wow, some really wonderful work is taking place in Nate KA1MUQ's basement in California. 

-- I really like the pill bottle coil forms.  I wonder if Nate faced suspicion (and possible arrest) in the pharmacy when he asked for the pill bottles.  (I got some suspicious looks when I went I asked for empty pill bottles while building my thermatron Mate for the Mighty Midget receiver back in 1998.) 

-- The variable capacitors are also quite cool, as is the big rotary switch.   Is that for band switching? 

-- Oh  man, all on a plywood board.  Frank Jones would approve!  

-- Indeed Nate, that beautiful receiver NEEDS an analog VFO.  And we need to hear it inhaling phone sigs, not that FT8 stuff. 

-- Please keep us posted on your progress.  And of course, one hand behind your back OM.  Lots of high voltage on those thermatrons.  

Thanks Nate!  

Monday, February 12, 2024

Dean's Amazing Homebrew sBITX

 
I was kind of making fun of  it during SolderSmoke podcast #250, but later that same morning I had a chance to watch the KK4DAS homebrew sBITX in action, in person, and I must say, it was very impressive.  This may be the only homebrew sBITX in the world (please correct me if I'm wrong).  

In the picture above you can see the amalgamation of traditional superhet with modern DSP.  Even for an HDR guy like me, the result is really cool.  Once again, I experienced waterfall envy.  And the sBITX receiver sounds great. 

Dean has written up his experiences with this rig in a blog post.  Check it out for more info: 


Thanks Dean! 



Saturday, February 10, 2024

SolderSmoke Podcast #250 Dean KK4DAS joins Pete N6QW and Bill N2CQR


SolderSmoke Podcast # 250 is ready for download: 

http://soldersmoke.com/soldersmoke250.mp3

VIDEO VERSION: (1707) SolderSmoke Podcast #250 -- With Pete N6QW, Dean KK4DAS, and Bill N2CQR - YouTube

Intro:   Welcome to Dean KK4DAS.  For 2024 Pete and I hope to jazz things up a bit by bringing in fellow homebrewers to talk about their projects.  Dean is our first victim.  Welcome Dean. 

Some good news:  Several new homebrew receivers are inhaling:  Armand WA1UQO in Richmond has an amazing looking regen.  Scott KQ4AOP in Tennessee got his DC RX working.  Mike AG5VG in Texas has been homebrewing BITX 20s and BITX 40s.  All are on the blog.  

Pete's report: 

-- Recent blog entries on filters,  SSB rig architecture, and of course digital VFOs. 

-- Phasing measurements, quadrature, and the Seeed Xiao RP2040

-- Error in QST article on early SSB transceiver.  ANOTHER ERROR!

--LC VFO on blog!  FB Pete!  

Dean's report:  

-- Tales of woe on the homebrew sBITX

-- Help from Farhan.  

-- Ground Bounce.  FFT Hallucinations.   Wisdom files.

SHAMELESS COMMERCE DIVISION:   

-- Whenever you are tempted to buy something from AMAZON, just start at the Amazon symbol on the right side of the page.  We get a cut from Bezos, and it doesn't cost you anything.  

-- You can try to do the same thing with E-bay.  We are finding a lot of great parts there. 

-- If you see a SolderSmoke post on Facebook,  please Like and forward. 

-- Become a patron!  Go to the Patreon page.  We put the money to good SolderSmoke use. 

-- Visit Mostly DIY RF and buy a PSSST kit!  

Bill's bench:  

-- Building yet another BITX dual bander.  15-10 again. Tried to use a 25 MHz filter left over from the earlier project, but I had to build another.  Built a new VFO using the variable cap and anti-backlash gear recommended by Pete.  Was a bit tough to get the receiver sounding good.   Had a diode ring as the second mixer, but went back to a singly balanced mixer. 

-- 10 meter AM -- Thanks to Jerry Coffman K5JC for mod. 

Other topics: 

--Counterfeit chips.  Why? 

MAILBAG: 

Wes W7ZOI 

Jim Cook W8NSA  Transoceanic BFO

Grayson KJ7UM -- Vintage Computer Museum

Chuck Adams --Glad to hear that Chuck is doing well.  

Frank Harris  K0IYE --  NO CHIPS!!!! 

ED DD5LP  Antenna software

Eldon KC5U  10 AM We  made a contact

Joh DL6ID  10 AM   

Phil   W1PJE of MIT   10AM   Where is L5? 

Bob WP4BQV now in UK 

Dino Papas KL0S in Wilmington   Reverse Polarity protection. 

AA7EE Dave Richards  Liked Armand's receiver

Rogier PA1ZZ  

Jonathan-san W0XO  Listened to my ET-2 CW Whoop,whoop

Nick M0NTV  Great videos from Nick the Vic

Will KI4POV  Working on his own SSB rigs.  

John West -- Who is the South American ham who made his capacitors and heat sinks? 

Ed KC8SBV  Working on DC receiver, experimenting with FETs 

Mike WN2A great contributions.  Si5351 sole source danger! 

Nick N3FJZ -- watch out for dead bands when testing receivers! 

Don KM4UDX encouragement from new Prez of VWS

Dave K8WPE Likes QF1 Cap backlash.  Says I'm getting soft! 

Dave WA1LBP My fellow Hambassador, from Okinawa USMC Sergeant with a workshop. 

Sunday, February 4, 2024

Scott KQ4AOP Successfully BUILDS a Receiver (Video) -- This is the Homebrew Spirit at its Maximum

This is just so cool.  Scott KQ4AOP has successfully homebrewed a ham radio receiver.  He used the circuit Dean and I developed (with a lot of input from Farhan and others) for the High School receiver project.  But Scott has had more success than any of our students.  And I think he has had -- in a certain sense -- more success than any of us.  After all, how many of us can say -- as Scott can -- that he used a homebrew receiver that he made to listen -- for the very first time -- to amateur radio signals?  Scott writes:  "Those first sounds were my first time ever hearing any Amateur Radio first hand!" 

In the email below, you can see Scott's deep commitment to homebrew: "I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear."  Wow Scott, the building of the receiver is the hard part, and you have already done that.  I think you are well on your way.  

In the video above you can watch Scott tune the entire 40 meter band and a bit beyond. You hear CW at the low end.  Then FT-8.  Then SSB.  Up just above the top of the band I think you can hear our old nemesis Radio Marti.  And this powerful broadcaster is NOT breaking through on the rest of the band.  FB Scott.  Congratulations.  

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

 Bill,


Thank you for the quick response, direction, and pointers. I won't give up, and I am not in a rush. 

I have wanted my amateur radio license since the early-to-mid-80s. I got my Technician and General in May of 2022 and completed my Extra in May 2023. I always wanted to understand how to design circuits, and I wanted to build them. I share that background to say that I have this impractical goal that I am stubborn enough to stick to (all due respect to you and Pete's advice on the topic of getting on the air). I want to build my own gear for 40m. I want to learn morse code. I want my first contact to be on my own gear. So, your blog and podcast really resonates with me. 

I am only teaching myself at this point. It was the perfect project for my goals. I thought that if all these high school kids in Virginia, Canada, and Germany can do it, it was the sweet spot I was looking for. 

The only transceiver I have was recently gifted to me. It is a Sommerkamp TS-788DX CB radio that allegedly works on 10m in addition to CB. I haven't connected it up because I wanted to stay focused on the HSR. I have a mentor who has gear that I can use to test the oscillator. I am not involved with the nearby ham club, but I know they would help if needed. 

Thanks again and I will keep you posted,

73 Scott KQ4AOP


Bill and Dean - Thank you for sharing and documenting this receiver. I greatly appreciate you publishing the circuit, class notes, and build videos. That got me 75% to completion.
I feel blessed that both of you chipped in and encouraged me through the troubleshooting to finally getting the receiver to start “breathing RF”.
Those first sounds were my first time ever hearing any Amateur Radio first hand!

Friday, November 10, 2023

SolderSmoke Podcast #249 -- Travel, Pete's 6BA6 rig, Books!, VFOs, SDR, Computers, Spectrum Analysers, Transistor Man! MAILBAG

New VFO for 15-10 Transceiver
Schematic below

SolderSmoke Podcast #249 is available:  http://soldersmoke.com/soldersmoke249.mp3

There is also a video version of this podcast: https://youtu.be/5xyaYivtOhw

Travelogue:  

HAPPY VETERANS' DAY TO PETE AND GRAYSON AND TO ALL THE OTHER VETERANS WHO ARE LISTENING. 

Trip out to San Francisco. Sticker placed on the corner of Haight and Ashbury:  See picture below.  Note other sticker.  Really Groovy! 

Bill's DXCC-100.  DONE.   

Tribal Wisdom:  W1REX on HRWB https://soldersmoke.blogspot.com/2023/11/listen-to-rex-w1rex-lots-of-tribal.html

Pete's Bench:

Pete's 6BA6 rig

Pete's 6BA6 Rig

Pete Re-invents the Shirt-pocket SSB Rig

Pete's remake of the ShirtSleeve Transceiver

Pete Builds Two Computers 

Pete Adds a Second Band to his Homebrew SDR 
 

SHAMELESS COMMERCE DIVISION:  

BEZOS BUCKS ARE BACK!  PLEASE  BUY THERE! >>>>>>>>>>>>>>>>>>>>>>>

Mostly DIY RF:  Work proceeds in the Oregon Silicon Forest on P3ST kit development. Todd is confident the P3ST will be released on December 18th.Many other kits available now:  https://mostlydiyrf.com/ 

Sign up for the newsletter:  https://mostlydiyrf.com/subscribe/ 




Bill's Bench: 

Rebuild of the 15-10 VFO (for improved Dial Spread) (with yet another QF-1 capacitor) https://soldersmoke.blogspot.com/2023/10/dial-scale-linearity-spreading-out.html

Why Building for 10 meters is harder: https://soldersmoke.blogspot.com/2023/09/why-building-for-10-meters-is-harder.html

Copper Tape shielding of 15-10 rig. 

Crushing Spurs with Better Bandpass Filters (see blog post) https://soldersmoke.blogspot.com/2023/09/crushing-17-and-12-meter-spurs-with.html

Another 15-10 rig in the works... for SSSS.   Boards are accumulating... 

More problems discovered with the Herring Aid 5 Receiver . Lots of SS blog posts  Comment from Rick WD5L.  ) https://soldersmoke.blogspot.com/2023/10/a-big-error-discovered-in-1976-qst.html   Did you try to build one?  Did you succeed or did you fail?  Please let us know. 

The Basil Mahon books (blog posts) https://soldersmoke.blogspot.com/2023/11/basil-mahon-is-author-for-us-he.html

The Sunburst and Luminary book of Don Eyles (blog posts) 

The Art of Electronics by Horowitz and Hill (blog posts) 

Spectrum Analysers:  Tiny SA Ultra https://soldersmoke.blogspot.com/2023/09/the-tinysa-ultra-spectrum-analyser-video.html  and Polarad 632C-1; George WB5OYP gave me one of these spectrum analysers  (I NEED a manual! Does anyone have a manual or a schematic? )  : 

Polarad 632C-1

Stabilizing the EB63A (with Pete recommended LP filters from e-Bay. 


MAILBAG:

TRANSISTOR MAN T-SHIRTS!  Thanks to Roy WN3F! 

Todd VE7BPO on AF amplifiers.  Thanks Todd.  

Wes W7ZOI -- Always a privilege to exchange e-mail with Wes. 

E-mail from Jay Rusgrove W1VD. About the Herring Aid 5. 

E-mail from Eamon Skelton EI9GQ!  Amazing! 

HB2HB with Denny VU2DGR https://soldersmoke.blogspot.com/2023/09/hb2hb-contact-with-denny-vu2dgr.html

Nick M0NTV on diode matching for ring mixers: https://soldersmoke.blogspot.com/2023/10/does-matching-matter-diode-matching-for.html

Paul Taylor VK3HN on the new Elecraft CW rig. 

Dean KK4DAS fixed the noise in his Hallicrafters SW receiver.  A long battle, finally won. 

Dean also in contact with G3UUR. 

Ramakrishnan VU2JXN helping me set up a backup of blog on WordPress.  

Mark KA9OOI noticed that SS podcast archive appears gone.  In fact just temporarily relocated to http://soldersmoke.com/podcastarchive.html

(SS PODCAST Archive temporarily relocated to http://soldersmoke.com/podcastarchive.html

Andreas DL1AJG - Crystal radio video. https://soldersmoke.blogspot.com/2023/10/building-crystal-set-videos.html

George N2APB on the Herring Aid 5

Grayson KJ7UM experimenting with Varactors and Thermatrons! 

Thomas K4SWL on Mattia's DC receiver. https://soldersmoke.blogspot.com/2023/10/mattia-zamanas-amazing-direct.html

Bob Weaver of Dial Bandspread Linearity  fame.  Electron Bunker

Mike Bryce WB8VGE QRP Hall of famer -- he too couldn't get the Herring Aid 5 working. 

Kirk NT0Z wrote about the Wayback machine.  But this former ARRL staffer he also tried and failed to get the Herring Aid 5 going.  Way back when... https://soldersmoke.blogspot.com/2015/03/kirks-herring-aid-tuna-tin-and-regen.html


New 15-10 VFO with schematic

Dial Bandspread (Before)

At corner of Haight and Ashbury

Saturday, October 14, 2023

Paul VK3HN's Video on Scratch-Building and SOTA


It was great to get a comment from Paul VK3HN -- this led to a re-establishment of contact.  Apparently Google knows who I have been e-mailing, so this great video appeared on my YouTube screen.  Thanks Google! 

-- Great to hear Paul's shout out to Pete Juliano N6QW, and Pete's concept of noodling. 

-- Paul's emphasis on testing each stage independently is really important. 

-- Wow, ferric chloride!  It is great to see someone doing this (instead of just sending Gerber files to China). 

-- Books.  This reminds me that I have to get Drew Diamond's books. 

-- Paul's comment on the usefulness of a general coverage receiver.  Right on target Paul.  

-- On the test gear, we can now add the TinySA Ultra.  And you don't have to win the Lotto! 

-- Finally, Paul is absolutely right on the need to constantly update and publish changes to schematics. I am guilty of not doing this. (I hang my head in shame.)   This became a problem in our simple High-School receiver project -- I would make changes to circuits and fail to communicate these changes to Dean KK4DAS.  Paul's method would have solved this problem.  

-- Thanks Paul! 

Saturday, September 30, 2023

The TinySA Ultra Spectrum Analyser (video)

I got mine this week, and I've been playing with it.  When I spoke to Dean KK4DAS, I asked what he thought the first thing I did with it was.  He guessed that I tried out the greatly improved Resolution Bandwidth.  Good guess, but not quite:  I tried out the  "listening" feature on this SA.  You will recall that the plain-vanilla, non-Ultra TinySA required a hardware mod to allow for listening.  Dean had told me that the Ultra came with a headphone jack.  Indeed.  I fired it up and was able to listen to 1220 AM and also to the FM broadcast stations in the area.  With the FM stations, I'm guessing I was using a form of slope detection (IMSAI guy says it detects AM).   I tried to see if I could see/hear stations on the ham bands -- so far, no luck.  I'm not sure why, but I will work on this.  

The IMSAI guy video (above) does a great job in comparing the TinySA Ultra to a "real" spectrum analyser.   I think it compares very well.  

One note on where I got mine:  I ended up getting it from R&L Electronics, the recommended U.S. dealer for the device.  I had tried getting it (cheap) through AliExpress.  This didn't really work out.  The tracking info from AliExpress showed that the box had made it to my local post office, but I never got it.  It may have been that they just didn't take the complete mailing address from PayPal.  In any event, I was able to get a refund from PayPal, so no loss here.  R&L turned out to be a great source. 

Ultra, of course. 

Sunday, September 17, 2023

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


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

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

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

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

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

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

More on "The Art of Electronics" to come. 

Friday, July 28, 2023

Phase Noise and the Radio Amateur

A weak signal disappears in the phase noise of the stronger signal.

The March 1988 QST provides a relatively clear explanation of what phase noise really is:

Highlights: 

Phase noise is an undesired variation in the phase of the signal. In this case, an oscilloscope shows that the time between zero crossings of the signal varies over time when compared to the zero crossings of an ideal sine wave. An exaggerated example of phase noise is shown above.

Phase noise on an oscillator signal has exactly the same effect as frequency modulating the oscillator with noise.

Whenever a carrier is passed through a mixer, the phase noise of the oscillator driving that mixer is added to the carrier.

Phase noise on a transmitted signal causes effects identical to phase noise generated in a receiver.

Any signal that reaches a mixer in the receiver is modulated by the phase noise in the local oscillator driving that mixer. As such, the signal appears to have at least as much phase noise as the local oscillator. Thus, sufficiently strong signals off the receiving frequency can degrade receiver sensitivity by raising the noise floor at the receiving frequency. Receiver dynamic range is reduced as the noise floor rises.

With a frequency-shift-keyed or- a phase-shift-keyed signal, the close-in phase noise limits the maximum bit error rate that the system can achieve. Both of these effects can be quantified once the communications system is defined. With an SSB voice signal, the effects are much harder to predict, but excessive phase noise does degrade SSB signal intelligibility to some extent.

--------------------------------
Receiver guru Rob Sherwood provides some very useful historical background on his web site:

http://www.sherweng.com/documents/TermsExplainedSherwoodTableofReceiverPerformance-RevF.pdf

Phase Noise: Old radios (Collins, Drake, Hammarlund, National) used a VFO or PTO and crystal oscillators to tune the bands. Any noise in the local oscillator (LO) chain was minimal. When synthesized radios came along in the 70s, the LO had noise on it. It is caused by phase jitter in the circuit, and puts significant noise sidebands on the LO. This can mix with a strong signal outside the passband of the radio and put noise on top of the weak signal you are trying to copy. This is a significant problem in some cases: You have a neighboring ham close by, during Field Day when there are multiple transmitters at the same site, and certainly in a multi-multi contest station. You would like the number to be better that 130 dBc / Hz at 10 kHz. A non-synthesized radio, such as a Drake or Collins, has so little local oscillator noise the measurements were made closer-in between 2 and 5 kHz.   

-------------------------------------
Experimental Methods in RF Design (EMRFD) has this to say about phase noise:

"The local oscillator is a critical part of any communications system. Modern transceiver performance is often compromised by LO systems that suffer from excess phase noise, effectively limiting the receiver dynamic range. While quiet oscillators, those with low phase noise, can be built using traditional methods, these circuits often lack the thermal stability of a synthesizer.... Frequency synthesis is not, however, the answer to all the LO problems presented to the experimenter.  Some PLL synthesizers are burdened by excessive phase noise. Those using DDS, while quieter, emit spurious outputs, often in profusion.  Both use an excess of digital circuitry that can often corrupt a receiver environment."  page 4.1
   
"At first glance, phase noise sounds like an esoteric detail that probably has little impact on practical communications.  This is generally true." page 4.12 

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

Hans Summers G0UPL analyzed and measured the phase noise of the Si5351a chip: 

http://qrp-labs.com/qcxp/phasenoise.html

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

DC4KU appears to be using the crystal filter method used by Hans: 

https://dc4ku.darc.de/Transmitter-Sideband-Noise_DC4KU.pdf

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

Martien PA3AKE has done a lot of great work on this topic.  See: 

https://martein.home.xs4all.nl/pa3ake/hmode/dds_pmnoise_intro.html

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

Dean KK4DAS commented on the phase noise video of the IMSAI guy: 

Watching the video I was reminded of Segal's law roughly paraphrased as follows.:

A man with one spectrum analyzer knows his phase noise. A man with two is unsure.

Wednesday, May 17, 2023

Farhan Visits Northern Virginia En Route to FDIM (Videos to Follow)


Mike KD4MM, Farhan VU2ESE and Dean KK4DAS

Farhan VU2ESE was in Northern Virginia this week, on his way to the Four Days in May Event at the Dayton Hamvention.   We had a great visit with Farhan.  We took him out to the Thomas Jefferson High School for Science and Technology where he shared with the students tribal wisdom about building CubeSats and about building simple direct conversion receivers.  Farhan's use of direct conversion receivers to teach homebrewing to students in Hyderabad inspired our efforts in Northern Virginia.  We often referred to Farhan when speaking to the students here, so it was really great to give them a chance to talk to him directly. 


From the high school we went to the local restaurant at which Vienna Wireless has its weekly lunch. Many of the people at this lunch are also members of the VWS makers group.  This was a lot of fun. 


Don KM4UDX even brought in his somewhat eccentric build of the uBITX transceiver designed by Farhan.  Don's rig is labeled "The uBITX of Life."  It has also been called "The Franken-uBITX." Whatever the name, Farhan was clearly pleased to see Don's handiwork. 

I shot a lot of video during Farhan's visit (last time I failed to do this and regretted it).  I will put these videos up on the SolderSmoke YouTube channel during the days ahead. 

Thanks Farhan! 

Tuesday, April 4, 2023

W2UO's Michigan Mighty Mite -- Made a Contact!

Hi Bill,

I found SolderSmoke about six months ago, and it's quickly become one of my favorite podcasts.

I've been a ham since I was 11, but never tried my hand at homebrewing anything.  I've always heard how hard it would be, and how a project like a SSB transmitter is just too far out of reach.

You and Pete are inspirational, so I set out to build a simple starter project, the venerable Michigan Mighty Mite.  However not just any mighty mite, a usable one, not just a proof of concept.  One intended to sit on a desk and look good doing it.  Complete with built in low pass filter, tx/rx switching, and an internal dummy load.

I don't know if I accomplished all that, but I did make a contact on it this afternoon.  Next logical step I suppose will be to build a DC receiver to sit next to it.

Please find pictures attached, I've learned a lot about what not to do with project, so criticism is welcome.

73!
-Jim W2UO



My response: 

Wow Jim, that is really wonderful.  Congratulations on the build.   I've built many of them, but I don't think I ever made a contact with a MMM.  FB.  

It looks great to me!   Indeed, you should do a Direct Conversion receiver next.    Maybe do a receiver for 40, then do a version of the MMM for that same band.  Then you could 
make a completely homebrew QSO.   I did this recently on 40:  https://soldersmoke.blogspot.com/2023/02/first-qso-with-high-school-receiver-100.html    It was a real hoot!  

Our friend Dean also built a MMM as his first project:  https://soldersmoke.blogspot.com/2019/12/dean-kk4das-puts-michigan-mighty-mite.html

Please keep us posted on your progress. 

Again, congratulations!   73  Bill N2CQR

Saturday, April 1, 2023

SolderSmoke Podcast #245: Cuban DSB, DC Receiver?, Can you spot the AI? (Prize), Winterfest Loot, Gina's Podcast, 6BA6 buy, MAILBAG

 
DC RX Example by KK4DAS

SolderSmoke Podcast #245 is available for download: 


Video:  (68) SolderSmoke #245: Cuban DSB, DC Receiver?, AI, Winterfest Loot, Gina's Podcast, 6BA6 buy, MAILBAG - YouTube

Travelogue: Cuba DSB and AM. Jose CO6EC and the Islander. We need more info, especially on the solid state Jaguey rig.

Bill’s bench:

Will the High School DC receivers get finished? Future uncertain. But the project was technically interesting. Great working with Dean KK4DAS. Battling AM breakthrough from Radio Marti. We joked that Dean has been listening to Radio Marti so much that even though he doesn’t speak Spanish, he has noticed an increased urge to liberate Havana.

Audio amps: Harder than we thought. Lots of variation in Hfe of 2n3904s. Oscillations.
Not using feedback amps nor LM386s, nor push-pull. Simplicity is a design goal.

Fixing the tuning (bandspread) problem on the VFO was fun.

Antennas? A quarter wave with ground or counterpoise works well. We tried it. 
(59) An Antenna for the TJ 40 Direct Conversion Receiver - YouTube
----
Back to work on the uBITX. I chickened out on replacing the predriver with a BFR-106, but then – Just in time Todd K7TFC and his Mostly DIYRF came out with BFR106 boards! TRGHS. I will do the mods on two uBITX transceivers. I even bought a solder-sucking iron for the second job.

Winterfest Hamfest. Big success. Thanks VWS. HERRING AID FIVE! Simpson 260! QF-1, Another Radio Shack DMM, Eamon Skelton’s Homebrew Cookbook, Knobs, SWR meter.
----

SHAMELESS COMMERCE: 
-- Todd’s Mostly DIY RF and the BFR106 boards, and much more: https://mostlydiyrf.com/
-- Become a Patreon sponsor of SolderSmoke: https://www.patreon.com/join/4785634/checkout?ru=undefined

----
Pete's Bench: 

Technical Note: Skype problems. Pete's Skype kept dropping out. Bad in the last podcast (#244). Three minute gap. I was ready to scrap the whole podcast when Dean KK4DAS offered to help. And he is obviously well qualified: https://potomacofficersclub.com/speakers/dean-souleles/ Dean went to work with AI. And he was able to fill the audio and the video gaps. Can you spot the three minutes of AI? Send me an e-mail with the time segment of the AI/Deep Fake portion of SolderSmoke 244. The first one with the correct answer will win a prize. 
SolderSmoke #244:
Thanks Dean!

----Interview on his Pete's daughter’s podcast. https://soldersmoke.blogspot.com/2023/03/listen-to-pete-juliano-on-his-daughter.html

-- 6BA6 e-bay buy. Will we see an all 6BA6 rig from Pete?

-- The NCX-5 on e-bay

PETE’S NEW BLOG: https://hamradiogenius.blogspot.com/

Mailbag:

-- A New SPRAT arrived in the mail. PH2LB’s Gluestick on the cover.
-- Will KI4POV – Awesome homebrew – on the blog.
-- Sands, VK9WX listening to SolderSmoke on Willis Island! Wow. 
-- Andreas DL1AJG in Germany continues with the Electronics for Biologists DC RX build.
-- Dean KK4DAS and his homebrew 10 meter DSB rig.
-- Jim W2UO built a Michigan Mighty Mite and made a contact.
-- Dave K8WPE and the E in IBEW. We need new stickers.
-- Bob KC4LB – Surface Mount is SMALL.
-- Bruce KK0S on the Herring Aid 5 Board.
-- Chuck WB9KZY on Nuclear Monopole Resonance very cool video – on the blog.
-- Alan WA9IRS wants a CW editor for his phone. Really.
-- Vic WA4THR also working on uBITX power out improvement.
-- Tobias weighs in on Kludge. As in Fudge.
-- Tony G4WIF notes that when he changes his oil he often removes sludge, not slooge.
-- Consultations with Lexicographer Steve KB3SII.
-- Walt AJ6T says CW operating declined after FCC ruling in 1970s about callsigns.
-- Ramakrishnan VU3RDD now VU2JXN has joined the VWS. An old friend of SolderSmoke. Urged us to launch a blog back in 2008. We announced his daughter’s birth - - now Ram is getting ready to build a DC receiver with her.

Sunday, February 26, 2023

First QSO with the High-School Receiver -- 100 mW to Dipole. (with videos) -- Homebrew to Homebrew!

  
Alan W4AMV in Raleigh NC

Dean KK4DAS and I have been working with a local high school.  The students are building a direct conversion receiver for 40 meters.  

We've been giving out prizes for the first team to complete each stage.   I wanted to give one of the teams a little oscillator that could b heard with their receiver.  So this morning, using a 7040 crystal from the AF4K (SK) company, I threw together a one transistor oscillator.  It has just 8 parts, including the key:
I had a low pass filter in the antenna tuner.  The antenna was a low-to-the-ground 40 meter dipole.  The transmitter was putting out around 100 milliwatts.   

N2CQR's Ten Minute Transmitter

The Reverse Beacon Network showed that I was getting out quite well: 


Then I thought, wait a second, let's make a contact with the prototype high-school direct conversion receiver.  

With the receiver hooked up, I again called CQ on 40 CW.  BOOM!   Very quickly Alan W4AMV in Raleigh NC  came back to my call.  Wow!  That's 222 miles.  And a quick check of QRZ.com revealed that Alan is a homebrewer.  Then Google reminded me that his work has been featured on the SolderSmoke blog.    TRGHS. 

I was so excited during this contact that I almost forgot to film it.  But I did manage to get some short clips of the QSO in progress.   You have to listen carefully, but you can hear our calls in there while Alan is transmitting (listen for the lower tone): 


And in this clip you can watch me transmit using the 10 Minute Transmitter: 


UPDATE (Feb 27 2023):  I asked Alan about the rig he was using:  "A PLL EXCITER DRIVING A PAIR OF FETS PUSH PULL ABT 50 w to an inverted L at 55 feet. The Rx a single conversion 9 MHz IF and it is connected to an active antenna in the trees out in the woods abt 25 feet up. Uses an automotive whip antenna about 3 feet long. "

Alan's Rig

This little contact is a reminder of the fun that can come from using simple, homebrew, QRP gear.  It is really amazing that the very first contact with this receiver was with another homebrew station.   This all reminds Dean and me of something we have been telling the students:  the little DC receiver they are building is not a toy -- it is capable of being used in real, long-distance contacts.

Thanks Alan!    

Saturday, February 25, 2023

Video by KK4DAS on Progress in High-School Direct Conversion Project


More info in blog post below. 

Progress Report: High-School Students Build Diode Ring Mixers (Board #2 of 4). Hyderabad Soul Added to the New Machines

Dean KK4DAS works with students

A team from the Vienna Wireless Society was back in the local high school Thursday and Friday of this week, helping the students finish their variable frequency oscillators and build their diode ring mixers.  Club President Dean KK4DAS was in the lead, and did an amazing job working with the school and procuring all the needed parts.  Mike KD4MM  and Don KM4UDX provided patient and understanding help to the students. 

Students at work on the receiver

On the oscillators, the students  had to add about six parts to install a buffer circuit built around a J310 FET.  They also had to replace some of the 3D printed coil forms for the main-tuning variable inductor. (Dean KK4DAS made some really nice forms -- see below.)   Several teams of students experiences were very pleased to get their oscillators running. 

Manhattan Mixer Pads

Then it was on to the diode ring mixer.  We had planned on having the students wind their own trifilar toroids, but we realized that this might be too much -- it would add a lot of time to the build, and would introduce a lot opportunity for error.  

One of Farhan's transformers

I remembered that Farhan had given me a big supply of FT-37-43 trifilar toroids that had been assembled in Hyderabad.  We decided to use these transformers.  We reasoned that this was not a big deviation from our DIY ethos -- after all, we didn't ask the student to wind their audio transformers, nor did they wind the RF choke in the VFO buffer.  But we faced a problem:   the Hyderabad transformers were all wound with the same color wire on all three turns.  This would make it hard for the students to figure out which wire went where (there were 12 such wires on each mixer board!).   I figured out how to do this:  The night before, I soldered together the center tap wires, and I twisted together the input coil wires.  We told the students to first solder the center taps in place, then solder the two free wires to the diode ring, and finally untwist the input coil wires, soldering in these connections.  This worked.  

How the transformers were prepped

Before we started, I gave the students a quick class on the essentials of mixers. And I pointed out that we were using transformers made in Hyderabad India and donated by our friend Farhan.  I told the students that whenever we include parts given to us by a ham radio friend we are adding "soul to the new machine." Indeed, Farhan's toroids added a lot of soul. 


We have been insisting that the students have each stage tested before moving on to the next.  This week we used signal generators to put RF and VFO energy into the mixers, and oscilloscopes to make sure that audio was coming out.  

One of the test set-ups for the mixers

The students are making good progress.  After today's session we did an estimate of where each of the projects stand at this point: 

We are building 15 receivers. 
Oscillation without the buffer:   11
Oscillation with the buffer: 5 
Mixer built and tested (but no diplexer yet):  5 
Mixer working, diplexer built  2

During the next month or so the students will build the bandpass filter and the audio amplifier, and put all the boards together to complete the receiver. 

Saturday, February 18, 2023

Progress Report: High-School Students Melt Solder and Successfully Build Oscillators

Dean KK4DAS and I were at the high school on Thursday and Friday of this week for the construction (by the students) of the variable frequency oscillator stage of their analog, discrete, direct-conversion receivers for 40 meters.  Most of the students have already obtained their Technician Class licenses, so they are already radio amateurs.  Both the licensing classes and the receiver build are being done with the assistance of the Vienna Wireless Society. 

A week earlier Dean and I had demonstrated how to build the oscillator stage using the Manhattan technique (isolation pads super-glued to copper clad boards), but this week was the first time these students were actually building anything like this themselves. 


We deliberately did not "spoon feed" the students.  We told them that while we would be on-hand to help, THEY would have to do the building.  They would have to layout the pads on the PC board, select the parts (from a table set up by Dean), and do the gluing and soldering.  We did not hand the students bags of parts, or prepared PC boards.   This was not going to be a kit building session.  We wanted this to be real homebrewing. 

We had parts for 15 receivers.   But on the first day there were more than 60 students.  So four students per project.   On the first day we actually ran out of soldering stations.  

We cautioned the students against dawdling.  We told them to get on with it, and to "make haste slowly." We also injected an element of competition into the build by announcing that the first team to achieve oscillation would win.  (Prize still TBD).   

By the end of the Thursday session, many boards had been built but there were not yet any oscillations. We reconvened on Friday afternoon -- Dean and I set up support/troubleshooting stations. 

Right off the bat, one of the students came up with a board that he wanted to test.  After one quick correction (enamel still on the oscillator coil leads), my frequency counter showed that it was oscillating.  I fired up my DX-390 receiver and we heard the loud tone.   We had a winner! 

In the following hour or so, Dean and I did troubleshooting on about 10 more boards.   We found some of the problems that we would all expect (because we have all made these mistakes ourselves!): 

-- There were cold soldering joints.  We showed the students how to properly solder -- usually they just had to re-heat some cold-looking connections. 

-- A few of the Zener diodes and transistors were wired in backwards (been there, done that).  

-- A few of the feedback capacitors were of the wrong values.  Dean and I had brought some good caps, so the students were able to quickly swap out the parts.  This was another good lesson. 

-- There were a few wiring errors -- these were quickly corrected. 

It was exciting.  One-by-one we would hear the whoop-whoop as the DX-390 confirmed that another oscillator was OSCILLATING!  The students really liked to HEAR the oscillations that they had created.  We reminded them at the beginning that they would be taking DC from a little square 9 volt battery and turning it into RF that could (if connected to an antenna) be heard around the world, or in our case be used to receive signals from around the world.  

We got eight of the oscillators going.  We think the students will be able -- without much help from us -- to get the remaining seven oscillators going.  

They learned a lot.  They learned about the ease, flexibility, and usefulness of the Manhattan technique, and we think they could see how this represents a basic kind of PC board design.  Their soldering skills improved a lot. And they learned how to troubleshoot:  Is the layout correct?  Are any parts wired in backwards.  Is the soldering OK?   Are any of the parts bad (or of incorrect values)?  Most importantly, they learned that they CAN build circuits themselves, and actually get them working. 

The real payoff came each time oscillation was achieved. The students were really amazed and pleased.  I could tell that some of them weren't really sure their little device was actually creating the signal they were hearing.  So while we listened to the DX-390, I asked them to disconnect and reconnect the battery.  Confirmed.  Oscillation!  Smiles.   It was really great.  

Soon, after finishing up some PTO odds and ends,  we will move on to the other stages.  We'll probably do the bandpass filter or the mixer next.   Then the AF amp.  Then put it all together into a full receiver.  We think each stage will get easier and easier to build as the students learn and improve their homebrewing skills and their self-confidence. 

We've often reminded the students that what they are doing is NOT easy.  This is hard.  As new radio amateurs, they are taking on a project that most older hams never dare to take on.  They like the challenge.  They are homebrewing a real receiver. 

Tuesday, January 24, 2023

Update on High School Direct Conversion Receiver Project + .asc File


So far, in response to my recent request for testing,  no one has stepped up to build the DC receiver Dean KK4DAS and I are testing out.  We did get a couple of comments explaining why guys are opting not to help, but so far no other builders are actually melting solder in response to our recent request. 

So Dean and I decided to each build second versions of the receiver.   That will bring the total finished build population to 4.  I finished my second version yesterday.  Picture above.   It works great.  

One change:  The emitter resistor on the final AF amp was too low in value.   The transistor and the transformer were getting hot.  I switched from 10 ohms to 100 ohms and the problem disappeared.  I have made the change on the LTSpice Schematic.   Here is the .asc file (I hope!) : 

http://soldersmoke.com/DCRX.asc

Dean posted the .asc file (and some other info) here: 

http://bit.ly/3WAFfLI

If you have trouble accessing that file, please let me know and I will try to e-mail it to you.   In any case the schematic appears here: 

https://soldersmoke.blogspot.com/2023/01/a-call-for-builders-please-help-us-test.html

You will notice that this Spice schematic actually works!  The PTO turns on, and I put a simulated RF signal at the antenna port.  Audio appears at the output.  

Time is getting very tight.  Dean and I will begin presenting this project to the high school students on February 2.  So it is not too late to help. But helping is, of course, strictly voluntary -- if you are reluctant to build this thing, DON'T!   

Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column