Mike KA4CDN's Engraved SolderSmoke Direct Conversion Receiver -- Another VWS RX!

Mike KA4CDN is an experienced homebrewer and a member of the Vienna Wireless Society.  He took the SolderSmoke challenge and built the direct conversion receiver.  Congratulations Mike, and welcome to the Hall of Fame!  

Mike writes:

The goal of the project was mainly to test my conversion of my Ender3 3D printer into an engraver for making PC boards. Thank you Bill and Dean for leading the project. It had been a while since my soldering iron was hot on an RF electronics project. It is amazing how fast I get rusty and forget stuff. Now I'm going to pick back up on my crystal filter that I started I think two years ago

 ;-(  Awesome! 

For more information on how you too can build the receiver: 

Join the discussion - SolderSmoke Discord Server:

https://discord.gg/Fu6B7yGxx2

 

Documentation on Hackaday:

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

 

SolderSmoke YouTube channel:

https://www.youtube.com/@soldersmoke

Wes W4JYK's FB SolderSmoke Direct Conversion Receiver by a Vienna Wireless Society Makers Group Member

I was very glad to see Wes W4JYK finish this reciever.  Wes is a member of our local radio club -- the Vienna Wireless Society, and is part of the club's Makers Group.  

Wes writes: 

The DCR is up and running.  Listened to East Cars Net along with a few other stations.  Very cool! and good project.

Thanks Wes and congratulations on entering the Hall of Fame!

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

For more information on how you too can build the receiver: 

Join the discussion - SolderSmoke Discord Server:

https://discord.gg/Fu6B7yGxx2

 

Documentation on Hackaday:

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

 

SolderSmoke YouTube channel:

https://www.youtube.com/@soldersmoke

Radio Items Picked-up at VWS Winterfest 2024 Hamfest

As always, click on image for a better view

Above you can see what I picked up at the Vienna Wireless Society's 2024 Winterfest Hamfest. 

-- On the left in the blue box is an MXM Industries SuperRX/TX 40 transceiver. It is a kit from a Texas company.   Superhet receiver with IF at 455 kHz.  Crystal controlled CW transmitter on 7040 kHz.  The oscillator works, but so far no receive signals.  I will have to troubleshoot.  Does anyone have a schematic? 

-- Behind the MXM there is a nice box marked "Diode Detector" I opened it up and there is just a solid state diode and a 50 ohm resistor to ground.   Box may be useful. 

-- I got a couple of books: "Weekend Projects" 1979 from ARRL, and "A History of QST -- Volume 1 Amateur Radio Technology 1915 - 2013" 2013 from ARRL. 

-- On top of the Weekend Projects book you see a "Crystal Holder" from Gross Radio of New York City.  W1UJR has some good history on this company:  https://w1ujr.com/written-word/gross-radio-company-circa-1931/  This device seem to be intended to hold in place a raw piece of quartz!  Cool. 

-- To the right of the books there is a serious-looking VFO.  One dollar!  Deal!  It is a CB VFO, but the markings say it puts out 5.44 to 5.99 MHz.  So it should be useful.  The dual speed dial is very nice.  

-- Above the VFO is a nice step attenuator from the "Arrow Antenna" company of Loveland Colorado. 

-- Further to the right are some Electric Radio and Antique Wireless Association magazines that Armand WA1UQO gave me.  Really nice.  The AWA mags have a very thoughtful piece (warts and all) on Jean Shepherd.  And the ER pile has an article by Scott WA9WFA that mentions my work on the Mate for the Mighty Midget receiver.  Thanks again Armand! 

-- I also got some ADE6+ surface mount mixers.  The price was right! 

Thanks to VWS for putting on this great hamfest! 

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! 

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. 

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)

Checking Into the Vienna Wireless Pow-Wow Net after 23 Years!

 

I used to check into this net with my HW-101 from 1996-2000.   Last night I fired up my uBITX, hookied it up to my CCI .1 kW amp, and tuned the 75 meter doublet for 10 meters.  Bill AF4LL (Mr. 10 Meters) was net control.   Mike AE4R was also on frequency -- he was there the last time I checked in too.   It was fun.   

The QSL card shows the transceiver with the LiPo battery that was powering it. 

My HI7/N2CQR QSL Card

My fellow Vienna Wireless Society Member Ron WA6YOU is a real expert collector of QSL cards.  He was rightly critical of a very crude homebrew QSL that I made a while ago.   So when I got back from the Dominican Republic I decided I had to clean up my act.  Some Googling, some printer ink, and some cardstock later, I came up with the above.   I kind of like it -- it looks better (believe me!) than my earlier effort, but it retains an element of homebrew (I kind of made it myself).  

The picture is of Juanillo Beach, the beach we use when in Cap Cana.  This one was filled out for Mike KA4CDN, who was the only Vienna Wireless Society member I contacted from HI7.  

I made about 38 contacts from HI7.  If anyone out there worked me and wants a card, my printer is at the ready!  

To make the card, I used:  https://www.radioqth.net/qslcards

Working Vienna Wireless Society member (KA4CDN) from Hispaniola

We'll be heading back to the States soon and I was feeling guilty about 

not having worked anyone from my home club (the Vienna Wireless Society). 

On Wednesday night I Zoomed in to the club's Maker group -- this made me want 

to make at least one contact with the club.  Plus Walter KA4KXX  in Orlando has 

been trying to set up a sked on 20... This morning I saw that the SFI was up above 200. 

I lengthened the dipole so it would resonate on 20 meters (on this trip it started on 20, went to 17, back to 20, down to 10 and now, back to 20!). I worked one station on SSB, then sent a text to the club's DX spotter group, saying that I would be calling CQ on 14.060 MHz.   Soon I got a call from club member (and Maker) Mike KA4CDN.  We had a nice QSO.  Thanks Mike (video of our QSO above). I will try with Walter tomorrow.  

 

Dhaka Jack Moves to France

Jack Welch AI4SV has been an important member of the SolderSmoke community for many years.  I remember fondly our Straight Key Night CW contact in which he told me that my HT-37 had "presence" even on CW.  His thoughtful (!) piece on time crystals was also quite memorable.  Jack has finally settled down (a bit) after a string of foreign assignments.  He has landed happily in France, in a villa, on a vineyard, surrounded by wild boar and hunters.  FB OM. 

Hi Bill & Pete,

I've packed up the shack and moved from Cyprus to France, so no more 5B4APL. To obtain a French callsign, you have to submit proof that you've lived in France for three months, so I'm F/AI4SV until December and then we'll see. 

I'm not sure how long we will be here, but probably a few years at least. Since we know next to nothing about French real estate, we are renting for the first couple years -- a château on the outskirts of Bordeaux. Before you think that I've come down with delusions of grandeur, I should point out that in that area, château means an old, stone house that is hard to heat in the winter -- and particularly difficult to run wiring around. Antennas and grounding are going to be particularly challenging. The selling point for the house was not so much my hobby as its location in wine country. In fact, there is a Sauterne my house's name on it (although I have nothing to do with production of the wine, that's in professional hands).

Back in the early days of Soldersmoke, Bill used to occasionally mention the dreaded Italian wild boar, the cinghiale. I didn't think that would ever be terribly relevant to me, but it is. A couple days after arriving in the Bordeaux suburbs, a sanglier (French cousin of the cinghiale) strolled across a road as I came around a bend. We almost had a month-long supply of bacon, but I managed to steer around him.

Since it will be a while before all our belongings arrive and even longer to set up a proper station, I have focused on operating QRP in the field and activating SOTA summits. That has gone well, but I aborted my most recent attempt when I ran into a bunch of orange-clad rifle-toting hunters who were combing the mountain in search of sanglier. Apparently it's a big thing here. I decided to survive to activate the peak on another day.

Finally, I have attached a journal article, which at first glance doesn't seem to have a lot to do with radio, but kind of does. It turns out that both the human ear and violins have non-linear characteristics that cause them to function as audio frequency mixers. Looking through the article, you'll find some familiar looking formulas about mixing products, harmonics and resonance. If Bill wants to get away from ICs, perhaps his next rig could include a 17th Century Italian violin as a mixing stage.

Cheers & 73,

Jack
F/AI4SV

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

Hello Jack:  

Great to hear from you.  Wow, France!  You are rivaling my string of nice-to-go assignments.  FB OM.  Have fun.  

Yes, the Cingales.   Hunting season was always a bit of an uneasy time.  We used to dress the kids up in reflective vests.   One time we found a very drunk Italian hunter wandering around with a shotgun (that was kind of scary).  We would know when hunting season started by the sound of gunfire in the morning.    Kind of reminded me of other places!  

In retirement I have gotten back into VWS.  We are having a lot of fun.  Just yesterday 30 students at the Thomas Jefferson High School got their Technician licenses. They will soon build Direct Conversion receivers. 

As for mixing, what you sent reminded me of my early confusion on this subject.  In the SS book I describe the "Terzo Suono"  -- it is really just an additive heterodyne.  I confused it 

with a true mixing product.  But it was an educational confusion. 

Please keep in touch and let us know how things are going at the Villa!  

73  Bill 

Putting a Real LC VFO in My Ceramic-Resonator, Direct Conversion 40 Meter Receiver. LC JOVO! (Video)

This is the DC receiver that I built back in 2017-2018. I had used a ceramic resonator in the VFO. That receiver was on the cover of SPRAT magazine. It may not have deserved the honor -- recently Dean KK4DAS and I discovered that the ceramic resonator VFO drifted rather badly. So Dean and I are now building real LC analog VFOs. This is kind of an aside to a Virginia Wireless Society -- Maker Group project. This video shows my receiver working yesterday on 40 using the VFO that was recently thrown together.

More details on the original project (that used the ceramic resonator) here: 

https://soldersmoke.blogspot.com/search/label/DC%20Receiver%20Build

 The VFO circuit comes largely from W1FB's Design Notebook page 36.  I followed most of the conventional tribal wisdom on VFOs:  NP0 caps, often many of them in parallel.  Air core coil (in my case wound on a cardboard coat hanger tube). 

For C1 I used a big variable cap (with anti-backlash gears) that Pete N6QW advised me to buy on e-bay. Thanks Pete.   L1 is on the cardboard tube.  I only built the oscillator and the buffer -- I did not need the Q3 amplifier.  (The water stain in the upper left is the result of a heavy rain in the Azores around 2002 -- water came pouting into the shack.)  

I think the VFO is more stable than the Ceramic Resonator circuit. But I want to go back and give the ceramic resonator circuit another chance...  Miguel PY2OHH has some really interesting ceramic resonator circuits on his site. Scroll down for the English translation: https://www.qsl.net/py2ohh/trx/vxo40e80/vxo40e80.htm

Dean KK4DAS commented that VFO construction is as much an art as a science.  I agree -- there is a lot of cut and try, a lot of fitting the components you have on hand into the device you want to end up with.  You have move both the frequency of the VFO AND the tuning range of the VFO.  Mechanics (in the form of reduction drives) is often involved.  And, of course you have to apply lots of tribal knowledge to get the thing stable. You could, of course, avoid all of this by using an Si5351, but I think that moves you away from the physics of the device, and is just less satisfying. 

So,  JOVO!  LC JOVO!  The Joy of VARIABLE Oscillation!