SolderSmoke Podcast #251 Aurora! CBLA, Winterfest, Legal Action Against SolderSmoke, HB sBITX, SDR, Raspberry Pi, Rounded Passbands, MAILBAG

Aurora Picture by Dean KK4DAS

SolderSmoke Podcast #251  4-1-2024

Audio: http://soldersmoke.com/soldersmoke251.mp3

Videos: Podcast 251 Aurora! CBLA, Winterfest, Legal Threat, sBITX, SDR, RaspPi, Rounded Passbands, MAILBAG (youtube.com)

Travelouge:  Dean goes to the North Pole to see Aurora. 

A CBLA Call to Arms! 

Winterfest.  Lots of goodies.  MXM Industries 40 meter transceiver. 1 dollar. 

Jean Shepherd. Recording of Bill talking to Shep in 1976.

Legal Trouble: Could put us out of operation for a while.  We need listener input. 

November 2023

December 2023

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Pete's Bench

Homebrew SDR (based on Zl2CTM’s original design) and how good it sounds.

Raspberry Pi Zero W is now working on FT-8 with digital adapter.

Ferrite Cores at Digi-Key (a replacement for the FT-37-43 where  you buy 100 and the price is 21 cents/each)

ADE-6 –great specs in HF but more expensive than the ADE-1

For Pete's recent blog posts, go to this site and click on "Archive" in the right column: 

https://n6qw.blogspot.com/2024/03/march-31-2924-happy-easter-to-those-who.html

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Dean's Bench 

sBITX progress, McGyver-ing a lifted pad, replacing crystal on the CODEC board, sBITX success! See: 

https://kk4das.blogspot.com/2024/03/homebrew-sbitx-tx-modules-pa-lpf-and-mic.html

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Shameless Commerce Division:  Please use the Amazon link on the blog to start your Amazon purchases. And please consider using Patreon to support the podcast and blog.  We try to send extra content to our Patreon supporters. Mostly DIY RF --  Boards, Kits and Pete's PSSST

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Bill's Bench

More trouble with the 15-10 rig.  Rounded passbands in 25 MHz filter. See figure 4 in both links: 

https://www.arrl.org/files/file/QEX_Next_Issue/Nov-Dec_2009/QEX_Nov-Dec_09_Feature.pdf

https://www.networksciences.com/pdfs/tutorial.pdf

Experimenting with Balanced Mixers and Product Detectors. Paul VK3HN  Suggests the MC1496 chip; Walter KA4KXX points to SSDRA circuits

But it is on the air!  Using the PA from a BITX40 module and an RD06.  

Put an OLD dial from Pericles HI8P on 15-10 version 1.  Soul in the new machine.

Pericles' Dial on the 15-10 Rig 

Mailbag: 

Grayson KJ7UM's Hollowstate video. 

Mike WU2D's amazing 10 meter DSB transceiver. 

Jack AI4SV (Dhaka Jack) liked video of recent QSO with AzoresDSB rig

Mike AA1TJ and Dave AA7EE on backwaves and 100 uW QRPpppp

Dave G3UUR  on my curved passband problem

Alan W2AEW heard my only QSO with the MXM indsutries SupeRX/TX40

Wes W7ZOI, Mike WN2A, Walter KA4KXX. Farhan VU2ESE on passband, 

Ramakrishnan sent article about Charles Proteus Steinmetz.  Beautiful. 

Justin AC8LV built a receiver!  FB. 

San Francisco QRP:   KDOFNR TouCans Rig, and N6ASD Zinc-Oxide TX

Frank KC8JJL -- Another guy who heard first ham sigs from a homebrew rig. 

Nate KA1MUQ's homebrew thermatron superhet

Dino KL0S sent info on the PAL CB VFO I picked up at Winterfest. Airborne! 

Bob W8SX will be once again doing SolderSmoke interviews at Dayton.  Thanks Bob

Peter VK2EMU  Always good to hear from him.

Tobias Feltus -- Wisdom teeth removed, wondering if he will get sBITX hallucinations...

Rick WD5L continues to work on his Herring Aid 5

Ciprian YO6DXE wants to learn CW. No alerts from his FB Blog!

Todd K7TFC -- Likes CW, says it eliminates the Blah-Blah-Blah 

F1BFU's Amazing PSSST VFO

How to Feel Bad about Carrier Suppression (and How to Get Over It)

Version 2 of the 15-10 rig continues to give me trouble.  But I guess it is "good trouble" because I am learning from it. 

You see, after you build an SSB rig, one of the critical alignment steps is the placement of the carrier oscillator/BFO frequency in relation to the filter passband.  (The IMSAI Guy has a good video on this -- see above.)  You want to place this oscillator somewhere on the downward skirt of the passband curve.  This will add to the carrier suppression already done by your balanced modulator.  There will always be some carrier remaining from the balanced modulator -- putting the oscillator frequency on the downward skirt of the filter passband adds to the suppression the carrier remnant.  

But you can't overdo it.   If you place that carrier oscillator frequency too far down on the skirt, you will start to cutoff the low audio frequencies in your transmit and received signals.  You will notice that your once beautiful sounding receiver suddenly sounds tinny and high pitched.  Yuck. 

So you go back to the books and the websites.  You look at the passband promissed by the Dishal software you used to design the filter.  See below:  

Click on the image for a better view

Surely with a passband as nice as that one, you will be able to find the sweet spot where the carrier is suppressed and your audio remains pristine.  

But I couldn't do this with the 15-10 rig.  I was forced to compromise: I had to accept less than optimal carrier suppression for less than optimal low frequency passband coverage.  And here is why:

Click on the image for a better view

The curve above is a much more realistic picture of what my filter passband actually looks like (see NanoVNA picture below).  The curve above is from the AADE software.  I found out that the Dishal software DOES NOT factor in important things like Q or ESR.  Dishal treats all crystals as "loss-less radiators."  So when you get up to 25 MHz where Q is important, AADE and other programs will show you that your passband has become curved.  And you can see how this curvature makes it difficult to get the kind of carrier suppression and audio response we want.  

What my filter looked like in a Nano VNA

Click for a better view

Look, the rigs work OK.  The receivers sound good to me.  The carrier is so far down that no one can hear it.  I have to remind myself that we are using 'SSB-SC" -- suppressed carrier, not eliminated carrier.  I've worked a lot of DX with these rigs.  But still,  I would like to improve the situation.  It kind of bothers me.  Homebrewers will understand. 

I have been experimenting with different balanced modulators.  I started with the simple two diode, single transformer, singly balanced design from Farhan's BITX20.  It works fine.  But I think I get a bit better suppresson from a doubly balanced diode ring.  I may try an NE602 Gilbert Cell.   I may also try to build a higher Q 25 MHz filter using low-ESR surface mount crystals from Mouser.  Stay tuned.  

Thanks to W7ZOI, VU2ESE, WN2A, KA4KXX, KK4DAS, N6QW, W2AEW, and G3UUR for all the good advice and encouragement.  Please put any additional ideas in the comments below.  

SolderSmoke Podcast #248 -- Back from the Summer -- Spurs and Filters, S-meters, 6BA6 mania, Shirtpocket rigs, MAILBAG

The PsssT Kit, coming soon from Mostly DIY RF

SolderSmoke Podcast #248 is available for download: 

Audio: http://soldersmoke.com/soldersmoke248.mp3

Video: (800) SolderSmoke Podcast #238 -- Spurs and Filters, S-meters, 6BA6 mania, Shirt-pocket rigs, Mailbag - YouTube

Travelogue:  Trip to the Dominican Republic 3-9 August.  Thinking about the M0NTV video on mixers...  

Solder Smoke Shack South is almost done.   I am thinking about workbenches, operating tables and antennas.  How high should an electronics workbench be?   Table height?  Or workbench (woodwork) height?  

My son and I went to see "Oppenheimer"  Trinity test scene very cool.  They wanted to see if the gadget would work! 

Is the SolderSmoke blog completely archived on the WayBack Machine?  Please check and let me know.  Thanks. 

Bill's Bench: 

-- I've been working a lot of DX with the homebrew rigs:  Indonesia, Australia, Japan, Hawaii.  Lots of fun.  15 meters has been especially good. But the rigs still need work: 

-- M0NTV's video got me to put TinySA to work.  I found that output from dual banders could be improved.  Spurs and harmonics. Yuck.  I need more TinySA -- ordered the TinySA Ultra. 

-- Allison KB1GMX helped a lot.  EB63A amp was unstable, especially on 10 meters.  Higher frequencies are harder!  Tightened up shielding, negative feedback, and bypassing.  This all helped, but I found that I needed to take the higher frequency LP filters out of the amplifier box.  W3NQN filters are better, with steeper skirts and better 2nd harmonic rejections. NanoVNA proving very useful. https://www.gqrp.com/Datasheet_W3NQN.pdf

-- Also worked on the Bandpass filters for these rigs.  Farhan's comments on skirts of different filter configurations.  Some are "LSB" filters (with steeper skirt at the highest freq) and some are "USB" filters (with the steeper skirt at the lower frequency)  See diagrams on the blog page. So I built USB new filters for 12 meters and for 10 meters. 

-- Danger that my unshielded wooden box rigs might be inviting feedback.  So I shielded the 1510 rig with copper guitar amp tape (conductive adhesive).  Good stuff.  

-- Phase Noise rears its ugly head again.  See blog posts. 

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SHAMELESS COMMERCE DIVISION:  

Mostly DIY RF getting ready to release PsssT kits.  Target date:  December 18, 2023 (E Howard Armstrong's birthday).  https://mostlydiyrf.com/

Amazon Search box seems to have died.  I can't get it back.  Can anyone tell me what happened?  (There seems to be "explanations" from Amazon about this, but they are written in a strange language that I cannot follow.)  Something similar happened with the Google Ads on this blog page.  Apparently you can't have ads both on YouTube and blogger.  

But hey, there is Patreon for those who want to support the podcast and blog. 

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Pete's Bench

An S-meter for Bill? 

6BA6 Mania! 

QRP SSB with 6BA6

Shirtpocket rig re-build

Mailbag: 

Walter KA4KXX has a great article about homebrewing in the September 2023 QCWA Journal.  

 Steve KC1QAY -- Has joined the CBLA.  I sent him a 3579 crystal.  He built a MMM and experienced JOO.  And Allison KB1GMX is in his local radio club.  TRGHS. 

Ajay VU2TGG in Pune, India -- launching a high school receiver effort. 

Denny VU2DGR The Wizard of Kerala: https://soldersmoke.blogspot.com/2023/08/the-wizard-of-kerala-india-denny-vu2dgr.html

Joe VK4BYER working with kids a remote Australian community.  FB. 

Todd K7ZF -- Wants to get into homebrewing. Advised him to start small. 

Dean KK4DAS:  Fixing Hallicrafters Worldwide RX. Ciudad Trujillo!  Got question from Mark in the VWS Makers Group:  HOW DOES Michigan Mighty Mite REALLY Work.  See blog. 

Trevor Woods -- Info on Super Islander Mark IV made in Cuba from old CFL bulbs.  FB. 

Bob KD4EBM sent me some great stuff:  Sony SW receiver,  QCX Mini.  Made a CW contact with the QCX.  Felt virtuous -- it is going to the DR.  Thanks Bob. 

Peter KD2OMV:    One of the guys I worked with the ET-2 transceiver.  Great to hear from him. 

Armand WA1UQO   Richmond area radio museum? https://www.youtube.com/watch?v=BSCmljje1p8

Mike WN2A -- Sent me a great care package with lots of toroids.  A lifetime supply!  Thanks Mike!

Nate KA1MUQ got his Doug DeMaw receiver going after 38 years!  FB.  Been there, done that! 

Tony: G4WIF Liked Valveman video about Gerald Wells.  He visited him! https://soldersmoke.blogspot.com/2023/08/valveman-story-of-gerald-wells.html 

Dean KL7MA  Bill talked to him on 15 SSB.  He had worked Wes W7ZOI!  FB! 

SolderSmoke Podcast #247 -- Hating on the IC-7300, Pete Goes FT-8 with a KWM-1, Bill's 15-10 Rig, MAILBAG

Bill's 15-10 Rig -- Click on image 

SolderSmoke Podcast #247 is available: 

Audio Podcast:  http://soldersmoke.com/soldersmoke247.mp3

Video:  (482) SolderSmoke 247 -- Hating on the IC-7300, Pete goes FT8 (with a KWM-1), Bill's 15-10 rig, Mailbag - YouTube

Bill’s Bench:

The 15-10 Dual Bander.

n  10 pole crystal filter at 25 MHz.

n  G3UUR, Dishal, AADE and all that..

n  Testing woes.  Looked bad.  But it was a bad test cable. Duh.

n  VFO (Colpitts) at around 3.5 MHz.

n  Buffer blues:  Bad J-310s.  Beware!  

n  Variable cap from a Heath Q Multiplier

n  A bit of a black art – competing goals. Freq coverage, etc.

n  BFO needed an amp to turn on the diodes in the balanced modulator

n  TIA amps.   SIX dual direction TIAs.  18 transistors.

n  On a pine board (like Frank Jones)

n  Will use the N6QW all discrete AF amp.

n  Maybe an RD16 in the final?

n  Will build a second one for the DR.

 Shameless Commerce:  Mostly DIY RF and the PSSST kit.  Todd K7TFC reports:  “The P3ST is on track for Lee Deforest's birthday release (August 26th). I'm going to send out another newsletter on July 4th, and I'll give some details on P3ST development.” Results of Todd’s Survey.

Pete’s Bench

n  FT-8 on the KWM-1!

n  Presentation to the ham club.

n  Why the Icom 7300 is the anti-thesis of homebrew.

MMAILBAG:

-- SPRAT 195  Summer 2023, in the mailbox.  A happy day at N2CQR

-- Armand WA1UQO sent a wonderful book about Faraday and Maxwell… And told me Jim K8OI was heading to our area.  I met Jim at the VWS Field Day event.  FB.  Thanks Armand.

-- Tony G4WIF sent Father’s Day greetings.

-- Alvin N5VZH asking about electrolytics for his 2-B.  Hayseed Hamfest!

-- John AC2RL replacements for the IBEW.  We need to start over!

-- Steve “Snort Rosin” Smith WB6TNL was in the area.  Sorry I missed him.

-- Joh DL6ID helping us to track down origins of a homebrew receiver Grayson saw in Berlin.

-- Grayson KJ7UM was in Europe visiting his wife’s relatives.  But I think he is back in the USA.

-- Walter KA4KXX sent a QRP HB family portrait. 

-- Wouter ZS1KE sent info on surface mount soldering.

-- George Zaff KJ6VU Ham Radio Workbench – re-runs! Recommended audio processor.  Let me know how it sounds. 

-- Michael AA1TJ   Great to hear from him. 

-- Alan Wolke W2AEW on the toroids  he used in Diode Ring video.  Thanks Alan!

-- Dean KK4DAS, AI and SWR meter project  And new lexicon word:  Hamsplaining. 

-- Bob N7SUR --  Let me know we are semifinalists in the Hack-A-Day prize!  

The 15 - 10 rig from above -- Click on image

Nine Homebrew Transceivers by Walter KA4KXX (and some QRP and QRO RC planes)

 

Our friend Walter KA4KXX in Orlando recently sent us this really cool "family photo" of his homebrew rigs.  Be sure to see the key that explains the photo (below) FB Walter.  Thanks too for the model airplane pictures. (Click on the images for better viewing.) 

Walter wrote: 

I recently realized that I am now operating nine homebrew transceivers, which would fit nicely in an “aerial” photograph, so I grabbed my stepladder and everything did fit well in the frame.  Six of them come from the BITX side of the family, with #1 and #7 direct conversion and #9 a single conversion superhet but using the NE602.  More basic information is included in the sketch.

I tried a Si5351 VFO once in the dual-band rig #4, but by the time I built the QRP Labs kit with so much closely-spaced soldering, and then added sufficient filtering and amplification to properly drive a 50 ohm load, I was exhausted!

These nine were created during the past eight years, and were preceded by eight more transceivers that I can document, but those have all been disassembled, with many of the parts being used in these later rigs.  I build my transceivers to be operated often, and since 20 Meters has been hot lately, for example, my POTA Hunter log shows over 300 CW and SSB contacts in 2023 alone, so rig numbers 7 - 9 have been earning their keep lately.

In summary I have created a lifetime total of seventeen transceivers so far, and although I am nowhere near the fifty-plus tally of Pete N6QW, I did spend a lot of years instead homebrewing many radio-controlled model airplanes of my own design.  Two photos show one example that I flew in the 2011 Blue Max Scale R/C Contest at the Fantasy of Flight Museum in Polk City, Florida against some stiff QRO competition.

—Walter KA4KXX

High-School Students Successfully Avoid THE SHELF OF SHAME -- Update on the Direct Conversion Receiver Project

One of the first finished receivers

Dean KK4DAS, Mike KD4MM, and I had a good day at the local high school yesterday, even after a month of spring break and other absences.  We thought this might have been our last session at the school this year, so we strongly encouraged the students to GET THE RECEIVERS DONE.  We told them about the Shelf of Shame, and warned them not to half-way finish something that would gather dust at the bottom their parents' closet.  They were close to success!  It was time to finish the project. 

We warned them not to be perturbed if the receiver doesn't work the first time they power it up.  This is not "plug and play."  The receiver would likely need some trouble shooting, or at least some peaking and tweaking.  We noted that we often have to sort of coax a signal out of a newly built receiver. 

We soon had the students come forward with two projects that were ready for final testing.  Sure enough we found problems with both.  The solutions provided a lot of educational fun. 

The first group had not yet built the diplexer -- we advised them to skip over the diplexer for the moment -- just connect the output of the mixer to the input of the AF amplifier.  We can't let the perfect be the enemy of the good!  Build the diplexer later, but for now, get the receiver going.  They did, and a few minutes later they were receiving signals from Mike KD4MM's transmitter (on the other side of the lab). 

Then a second group came forward.  We put a San Jian frequency counter on the PTO output.  Uh oh.  Trouble.  Gibberish!  A wonderful troubleshooting session ensued.  With the student, we found that the signal was good at the output of the oscillator transistor, but NOT at the output of the buffer.  At first we suspected that the buffer was bad, but it was not.  Then we lifted the connection to the mixer and suddenly the buffer output was good.  So the problem was in the mixer!  When we disconnected the input transformer of the mixer from the diode ring, THE PROBLEM WAS STILL THERE.  So the problem was clearly in the input transformer.  Dean gave us a replacement transformer.  Soon all was right with the rig, and this group joined the ranks of the successfully completed receivers.   

I think that seeing that two groups had finished helped motivate the others.  Our announcement that successful completion would lead to a "Certificate of Completion" also helped.  But most of all, I think the natural desire to finish the job and avoid the "Shelf of Shame"  was pushing the students forward. 

Other news: 

-- Our stage-by-stage award program continued.  Last time we awarded "The Torry"  for the first successful bandpass filter;  this time we awarded "The Audy" for the first successful audio transformers. 

The Audies

-- We told the students that their work has been entered in a Hack-A-Day contest.  Most of the info and files on the project can be found on the Hack-A-Day site.  Check it out:  

https://hackaday.io/project/190327-high-schoolers-build-a-radio-receiver

-- We also told the students about Walter KA4KXX's very generous offer of a reward for the first students to check into the Florida Sunrise net.  (We had to make it clear that this offer is completely extracurricular and unconnected in any way from the school .)  The students were clearly intrigued.  Sunrise Net may get some new check-ins! 

-- We provided instructions on how to build a simple 1/4 wave reception antenna.  We also did a video.  

We had thought that this would be our last session at the school,  but at the students' request we will be back with them next week for another session.  We think there are at least five more receivers approaching the finish line. 

SolderSmoke Podcast #244 PETE IS BACK! TR-7, CK722, BFR106, HP8640B, High-School Receiver, 10 Min TX, MAILBAG

SolderSmoke Podcast #244 Is available:

http://soldersmoke.com/soldersmoke244.mp3

Video version at:

(118) SolderSmoke - YouTube

HE’S BACK! HOORAY! PETE JULIANO N6QW IS BACK! SOLDERSMOKE COMMUNITY WAS SENT INTO A COLLECTIVE FUNK BY PETE’S ABSENCE. ---------------- Pete’s TR-7 (SEE VIDEO ABOVE) CK722 The BFR106

Pete's new blog: https://hamradiogenius.blogspot.com/ ---- Update on the high school project: Mixers made. Harder than they seemed. First QSO with the DC RX. Allan W4AMV Homebrewer TRGHS Ten Minute Transmitter – Better than the MMM! AF4K (SK) crystals. Other supporting projects: Farhan in Hyderabad. Rick N3FJZ, Walter KA4KXX, Andreas DL1AJG Electronics for Biologists. Peter Marks VK3TPM (fighting the siren call of the Si5351) . Steven VK2BLQ built a beautiful one. Daniel VE5DLD will build three of them with his students. Orlando PY2ANE is building one in Brazil. This week: The Bandpass Filter. (Thank you Hans Summers) --- SHAMELESS COMMERCE DIVISION: BECOME A PATRON VIA PATREON. I am posting some fun stuff for the Patrons. AMAZON SHOPPING ADS Now on both the left and right columns. CHECK OUT Mostly DIY RF in the right hand column. ---- My HP8640B Lives to Fight another day. Two new DMMs A low-end Fluke and a AstroAI 6000 Electrolytic Replacement Controversy Continues

Mailbag: -- Dave AA7EE is blogging again! Yea! -- Mike Rainey AA1TJ back in the Hobbit Hole Building a WWVB receiver. -- Farhan is coming to FDIM. -- Tony G4WIF reminds us that 39 bucks for JUST a 60 MHz counter would be great! -- Dave VE3EAC again helped me fix my HP8640B. -- Dean KK4DAS finalizing 10 meter DSB rig. FB. Upgraded my NanoVNA. -- Mike KD4MM giving me a Nano VNA for the SolderSmoke Shack South. -- Ian VK3LA asked what happened to Chuck Adams content. Good question. -- Don ND6T and I have been discussing envelope detection. -- Nick M0NTV working on AM modulators. He has a new video. -- Ciprian YO6DXE built a Ten Minute Transmitter. -- Steve EI5DD Connacht Regional News: https://www.docdroid.net/YJAV800/crnews0223-pdf

Hyderabad DC RX Workshop

Farhan explaining the receiver in Hyderabad

https://soldersmoke.blogspot.com/2023/03/pictures-from-farhans-hyderabad-high.html

SolderSmoke Podcast #243 -- HI7/N2CQR, uBITX mods for 10 meters, High-School Direct Conversion Receiver Project Launched (Success!) Mailbag

 

DC RX and one of the PTO boards we built as demos last night. 

February 10, 2023

SolderSmoke Podcast #224 is available. 

http://soldersmoke.com/soldersmoke243.mp3

Video here: (32) SolderSmoke Podcast 243 (video) Hi7/N2CQR, uBITX, Success with High School Receiver Project - YouTube

Pete N6QW had technical difficulties this morning.  He insisted that the show must go on.  Pete will be back for the next episode. 

 

Travelogue: 

Bill in the Dominican Republic for all of January.  

HI7/N2CQR  Eastern tip of the island. uBITX and dipoles. 

20, 17, 10.  CW and SSB.  SSB was tough and I had reports of RF getting into the signal.

Went to CW. 

Worked VWS Mike KA4CDN, and Walter KA4KXX on 20CW.

Finally moved up to 10 CW.  Lots of contacts. Even though uBITX very QRP on ten.

I am modifying the uBITX now.  

Copper tape shielding to keep RF out.

 Low power out not the fault of the IRF-510s.  The problem is the 2N3904s.

Will replace with 2N2222 in To-18 cans.

Dean KK4DAS putting KD8CEC software into Arduino.  I gave up.

Who sent me this orphan uBITX?

SolderSmoke Shack South in final phase of construction.

 

SHAMELESS COMMERCE DIVISION:

Patreon!

Bezos Shopping!

 

DC Receiver Project

Local High School radio club. 

Simple:  Like Herring Aid 5 and Wes’s original.

Farhan’s four stages:

BP Filter, Diode Ring, PTO, AF amp. 

Simple Colpitts PTO SURPRISINGLY STABLE.

Simple and easy.  No chips.  No complicated circuits.

Guys have helped test out the design:  Rick N3FJZ, Walter KA4KXX,

Daniel VE5DLD, Stephen VK2BLQ and others. 

First session last night:  We demonstrated build of the PTOs.  

They worked (thank God).

 

Open Circuits book.

Envelope Detection Controversy

Save the Antenna – Book “Losing the Nobel Prize” K1JT

 

MAILBAG

--Dean KK4DAS 10 meter DSB!  Tiny SA ULTRA! FB

--John AC2RL on Elmer W3PHL DSB guy

--AC3K reports inventor of Fender Stratocaster guitar was a ham: W6DOE

--AF8E was doing POTA.  I worked him. He said my rig had presence. FB

--Alain F4IET FB DSB rig with mic in Cigar can!

--Daryl N0DP worked him on SSB.  He is homebrewing

--Steve N8NM was in for repairs but is on the mend.

--Rick G6AKG working with sub-harmonic mixers and logic chips

--Paul HS0ZLQ Built DC receiver but looking for something else to build. No DSB!

--Steve AB4I – Coherer, Jagadish Chandra Bose, and Marconi

--Eldon KC5U    Worked VK5QD right after me and mentioned SolderSmoke FB

--Todd K7TFC is building the DC RX.

--Tony G4WIF and Ian G3ROO using automotive relays for antenna switching. FB.

--Dave WA1LBP Great to hear from my fellow Hambassador (Okinawa)

Older post comments:

--Scott VO1DR was also in CF Rockey’s class! (Blog comment)

--Aurora Aug 4, 1972: Twelve people shared memories.  (Blog comment)

--Will WN1SLG Googled novice call and was led to my Novice log.(Blog comment)

A Call for Builders! Please help us Test this Receiver! Please Build this Receiver!

 

This is the Direct Conversion receiver that Dean and I have built.  We plan to have students at a local high school build it, starting in early February.   We would like to have some others build it, to make sure that the design is re-producible without problems.  

Please build this receiver!  But we ask that you build it exactly as per the schematic above and below. Innovation can come later -- for now we just want to make sure this thing works, that there are no errors in the schematic, and that it can be built by the students with minimum woe.  Thanks in advance! 

Dean or others with 3D printers may be able to supply the plastic form for the PTO inductor.  

We know of one other builder, but he is having some trouble.  We would like to confirm that this design is sound.  

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

Above is the screenshot of the LTSpice model of the 40 meter Direct Conversion receiver that Dean KK4DAS and I have been working on.  I will post a larger scale version of the picture below.  Click on the images for a better view.  Comments welcome.  Please let us know if you find any errors or mistakes.  Realize that we wanted to keep this all simple, discrete, and entirely analog. 

Here (I hope!) is the net list for the LTSpice model: 

http://soldersmoke.com/DCRXLTSPICE.net  

First, one of the surprising things about the LTSpice model: IT IS ALIVE!  I never had a VFO or PTO actually turn on for me in LTSpice.  This one did!  So I just connected the PTO to the Mixer and the receiver works in LTSpice.   I just put an RF signal at the receiver input, and you can see the resulting AF across the 8 ohm resistor at the audio amp output.  I was even able to calculate the precise frequency of the PTO:  7078 kHz.  As in the real world, in an effort to stabilize the frequency, I changed the capacitors to NP0 in LTSpice.  Very cool.  Dean joked that all we need is a way to get RF in and audio out and we will have made an SDR receiver.  

About the receiver:  

--  Four stages that will be built by students Manhattan-style on four copper clad boards: Bandpass filter, diode ring mixer, Permeability Tuned Oscillator (PTO),  AF Amplifier.  

-- The bandpass filter is a simple dual-tuned circuit device based on the info on the QRP Labs site.  (Thanks Hans!)  We out a 10k pot as an RF gain control between the antenna and the filter. 

-- The mixer is a standard diode ring.  We included a diplexer at the output using a circuit from the famous W7EL  Optimized transceiver. (Thanks Roy!) 

-- The Permeability Tuned Oscillator is a very simple and very stable Colpitts design developed by Farhan VU2ESE.  We added a simple FET buffer using the circuit in Farhan's Daylight Again rig.  (Thanks Farhan!) 

-- The AF amp is a very simple three transistor amplifier based loosely on designs from Forrest Mims and from the Herring Aid 5 receiver. Both these designs use just two stages -- we added a third and put an AF gain pot between the first and the second stages. There is an impedance mismatch between the diode ring and the AF amp, but we found that most of the proposed solutions were more trouble than they were worth, so we left it as is.  

--Thanks to Wes W7ZOI for his November 1968 QST article on the solid-state DC receiver. Wes's article inspired our efforts.  

Dean and I have both built these receivers.  They work very well.  Dean has even decoded FT-8 with his. We used Radio Marti at 7355 kHz to test for AM breakthrough -- with the diode ring, the diplexer, and the RF gain control we were able to bring the AM breakthrough down to acceptable levels. You can see many videos of my receiver in action over on my YouTube channel:  (355) SolderSmoke - YouTube

Here is a larger image of the schematic (click for a full view): 

And here is a nicer schematic done by our friend Walter KA4KXX: 

Working Walter KA4KXX from Hispaniola

 Walter KA4KXX in Orlando has been a prolific builder of rigs for many years, and has been a great friend of SolderSmoke:  Here are some of the SolderSmoke podcasts and blog posts in which Walter's solder melting was mentioned: https://soldersmoke.blogspot.com/search?q=KA4KXX

As we approach the end of our current stay in the Dominican Republic, I could not miss out on the chance to work Walter with his homebrew rigs.  Even though the space weather was stormy, and my dipole was droopy, we arranged to meet up on the high end of the 20 meter CW band this morning.   See the results in the video above.  A solid QSO with Walter.  He says it is HB2HB, but truth be told I was on a uBITX that was built more by Farhan than by me.  But this was a great contact.  Walter started with a 50W rig, then switched to his 3 watt rig with a DC receiver.  FB

Here is the e-mail I received from Walter after the QSO: 

Dear Bill:

Many thanks for the great video, and when

you return to Virginia look for your mailman

to bring a postcard from me!

Just after your phone call this morning I scanned

the band from 14.025 to 14.300 and heard only one

SSB QSO at 14.347, and even now I only hear

a half dozen SSB signals, so that makes what

we did even more amazing. 

The first photo below is my 3.5 watt NE602 direct conversion 

rig which is about 2 years old.  The transmit signal is created

by putting a 3 MHz VFO signal into an NE602 mixer with an 

11 MHz crystal, so the rig can receive CW and SSB from 

14.025 to 14.300 and can transmit CW anywhere in that range

with good frequency stability. 

The bottom photo is my new full break-in CW 50W rig which 

I just put on the air about a week ago and is still in the finalization stage.  

I am not yet happy with it, but then again I am more particular

now than I used to be.  It is really a trans-receiver with a single 

conversion superhet receiver at the bottom of the board using 

an NE602 pair with a 3-crystal 4 MHz 900 Hz bandwidth filter, 

and a single 10.080 crystal VFO which is tuned with a polyvaricon

for operating between 14.061 and 14.068 MHz.  

At the top is the VXO transmit section using a pair of 14.070 

crystals pulled down into the operating range.  This signal

is buffered and amplified to about 500 mW which is all that 

the MRF101 RF Power Amplifier needs.  Visible behind the

board is an AC-powered 24 VDC switching power supply which 

is connected in series with the 12 VDC battery to 

power the final stage with about 36 VDC.  The main 12 VDC is 

provided by a bench power supply which is not in the photo.

In both rigs the morse code key is the microswitch 

at the lower right corner.  (Way more handy and elegant 

than your key, I might say?)

This morning each of these rigs was connected to its own

end fed half wave antenna, one in my backyard 

and the other on the side of my house.  My antenna analyzer

shows them to be essentially equal, but my 50W rig does

not like one of them at all.

Making our international homebrew-to-homebrew contact 

today was a terrific ham radio experience, so thanks for all 

you do!

73,

Walter 

KA4KXX

Orlando, FL