Voltage Regulators as Audio Amplifiers - Who Knew!?

Mike KC7IT pointed out that the AF amplifier chip in my Sawdust regen receiver is actually a TL431 voltage regulator. Mike writes: "It's using the voltage reference input as audio in, and the voltage being regulated as the audio out."  It works great as an audio amplifier, and with just three terminals it is a lot easier to use than our normal LM386 or 741 chips. I'd never seen a regulator used this way.

Here's the data sheet:  http://www.ti.com/lit/gpn/tl431

And here are a couple of sites that discuss this very interesting repurposing:

http://theradioboard.com/rb/viewtopic.php?t=6733

http://techlib.com/electronics/audioamps.html#TL431

A Regen that is NOT Evil

Look at that thing.  It is already painted Juliello -- this is a very good sign.  Steve Silverman sent me one of these Sawdust Regen kits a few years ago.  I put it together this week for my nephew John Henry who is very interested in Morse and ham radio.   

This is a regen that even I can love. It is simple, small and stable.  40 meters comes booming in.

Look at the schematic.  Why haven't we used that simple three-terminal AF amp IC before?   

Get your Sawdust Gear here: https://breadboardradio.com/breadboardradio/Products.html

International Brotherhood and the BITX Rigs

Bore and Heriberto's uBITX board

Nowhere is the International Brotherhood of Electronic Wizards more evident than in the work on the rigs designed by Farhan.  With the BITXs we see rigs designed in India that are now being built and modified all over the planet. Here are just a few examples of the global collaboration currently underway:

In Italy, Giuseppe is putting a BTX40 on 20 meters and making it a dual bander: 

Hi everyone, I just completed some tests on a Bitx40 running in 20 meters band. I addes the 20 as secondary band activate when needed. I apply some mods to switch to secondary QRPLab BPF filter centered to 20 meters and removed the C91 and C92 caps to work in USB. I done some RX tests in the weekend of iaru hf contest to listen some stations Active.
Here the issues registered:
1) the 20 RX sensitivity was a bit weak compared to 40 meters. I need to increase volume. ( To receive the 20 meters the vfo run to 26 MHZ, mybe some stage suffers of poor performance in this High frequency?)
I also tryed to increase the vfo over maximum allowed by raduino, using external buffer, but no results.
Please read the issues as: work but could work better!

2) the RX was not very clean: voice acceptable, but RX of Digital mode not very stable ( probably the cause could be the vfo shift for poor tuning control. I need to add lock function in firmware ...) Or interferences for free wire of connection.

3) Sometimes when switch on or change vfo to other band or mode, the bf amplifier start a self oscillation ...Resulting in my wife's screaming (the tests were also performed during the night!)

No tests was performed at the moment in TX because i need to install the LPF for the new band.
The firmware to make the test was a modified version of 1.17.1, few temporary mods to preset the vfo b to 14 MHz USB and correct the freq. Display.

These my tests.
Giuseppe Callipo IK8YFW.

Pavel is a young fellow in Cuba who is doing great things with the Raduino software: 



Hi to all.

The code was updated, the change log is this:

v1.4Update to catch up with the features added in the Raduino v1.17.1 from Allard's code (CW SPOT and bug fixes)

• Upgraded the operations instructions
  • More user friendly version with embedded images.
  • Add instructions for the S-meter, AGC and TX-power mods details and tricks.
• Moved all images to its own folder "images".

As usual tips/bugs/comments/suggestions are welcomed, you can reach the code here: https://github.com/pavelmc/bitx40/

There is a inoffensive bug in the calibrate process, in which the actual calibrate value is not correctly showed in the LCD until you move the pot to adjust it, I'm working on it.

I'm slowly working in this direction now:

• Bug removal in the calibrate function.
• Finish the upgrade of the Si5351mcu lib with some improvements.
• Adding CAT support via ft857d lib (https://github.com/pavelmc/ft857d):
• Full compliance needs get rid of all the blocking delay() sentences and that need a structural/paradigm code change and a lot of testing (I have Fldigi/MixW/Hamlib to test, I think if that 3 works the rest will do it)
• Moving to a library (yatuli: https://github.com/pavelmc/yatuli) for the pot usage, that will ease the process of implementing the CAT as almost all delay() calls are related to pot/clicks, so I'm on it.
• Maybe implement a multiclick lib to optimize the code and make it more easy to understand.

 Any thoughts or whishes related to that?

I plan to make the CAT operation optional via a #define declaration as not all of us will/want-to use that.
73 Pavel CO7WT

Here we see Bore in Montenegro working on a uBITX designed in Cuba by OM Heriberto

Hi Colleagues

Bore Lezaic from Montenegro is working on the uBitx PCB designed by Heriberto -CM2KMK- from Havana, Cuba

Here some pictures he(Bore Lezaic) have posted in my FB wall.

Any question regarding uBitx PCB please send to Heriberto Gonzalez Mendoza at cl2kmk@frcuba.cu (please take care with the email address it is slight different to his actual call sign).
Qrv's
73's Jc

Bore and Heriberto's Board

Hidehiko in Japan was struggling with some LCD noise in his experimental BITX40.  I passed along the active filter circuit that I'd first seen in Roy Lewallen's Optimized QRP rig. 

To

BITX20@groups.io Jul 29 2017 at 4:22 AM I've finished the Bitx40 experimental project today. I added the AF-AGC and LM386 POP limitter with raduino v1.20.1 (Thanks Allard). And I also added the DuinoVOX for Digital Mode operation. It's a great radio but the problem is only the "LCD noise" when increasing the AF volume. hi... Can I reduce this noise? Or I have to use the analog VFO? Any suggestions welcome.
ja9mat Hidehiko

To Hidehiko JA9MAT: 

Very simple.  Just three parts.   NPN transistor (like a 2N3904) and a 47k resistor (collector to base) 100 uF cap (base to ground).   Vcc the collector. Emitter goes to the DC power input of the AF amplifier.  You can see my use of this circuit in the schematic in this blog post:
Look in the lower right, near the LM386 AF amplifier.  Click on the schematic to enlarge.  73  Bill N2CQR 

My Organic Chip Rig with an LTSpice Schematic

Thanks Bill,
Well I added "3-parts"(2N3904+47kohm+100uF) between the D18(1N4148) and the junction of R111(100ohm) and R1113(220ohm). The noise has absolutely gone!
ja9mat Hidehiko.

_._,_._,_

ZL2CTM's Homebrew Transceiver Project

Wow, Charlie has a lot of very cool ideas in this initial video.   Some suggestions: 

-- With the IRF-510 in the final, beef up the heatsink, and follow Farhan's lead by including an option for 24 volts on the drain.  That would take you  up to 20 watts or so (for those who are so inclined). 

-- Could that Teensy SDR board work at the IF frequency?  If so, consider putting it ahead of the crystal filter.  This would enable us all to join the Waterfall Signal Purity Police Force. 

-- I love the OLEDs too, but I found them to be noisy.  I minimized the noise with shielding around the OLED and active decoupling on the power line to the AF amplifiers.

More of Charlie's work here: 

https://plus.google.com/107506245856154702088

Audio Clips from N2CQR/HI8 Contacts with MIR Space Station (now in mp3)

Back in 1995 I was in the Dominican Republic.  I used an old 2 meter rig and a homebrew 5 element quad (see below) to talk to U.S. Astronaut Norm Thagard on the MIR space station.  (You may have heard me bragging about this before.) I made a bunch of audio clips from the contacts.  They'd been in the now defunct RealAudio format, but I have been able to convert them to mp3.  You can listen here: 

http://www.gadgeteer.us/CLIPS.HTM

Real-Time 3D on an OLED Display

Oh man, I thought I was so cool when I got the OLED to display 7215 kHz and other frequencies.  Then I see this.  What next?  Real-time 3D SDR Waterfalls?  On an OLED?  Holograms?  

From: 
http://hackaday.com/2017/08/08/atmega328-3d/#more-267887

Alaskan Road-Kill Microphone

I got a kick out of Paul's message from Alaska -- on my bench I have an almost identical project, including the sink strainer (see below).  And of course the now-iconic SolderSmoke podcast mic is just an electret element inside what used to be an IKEA floor lamp. 

N2CQR Lamp Mic 

Hi Bill and Pete,

I have been following your and Pete’s adventures on Soldersmoke for a while and want to say that each episode always brings some of my past experiences to the surface.  I have been fiddling with radios and electronics for over 60 years, licensed since 1964.

I needed a mic for Bitx40 build and started thinking about this as I was working on other projects. Every day I walk a mile and a half to my mailbox. Wednesday’s and Friday’s happen to be the days of trash pickup and people put the trash bins out next to the road for pickup.  Last week I spotted a little desk lamp sitting on top of one of the trash bins with the cord cutoff so on my return from the mailbox it was still there and it followed me home.  (fig1)

Removing the shade left a flexible vertical support for a mic, (fig 2).

Your recent podcast you mentioned your D-104 microphone, that was my first mic once I had phone privileges back in ’65.  Scrounging through my treasure box I came across a 1 ¼” to 2” PVC pipe coupling that looked just like the basis for a mic. A few hours of mediation and a couple hours at the lathe and mill produced a mic with stand and a PTT switch (fig 3).

Some scrap bin aluminum and a free lamp from the trash and another hour at the lathe, (fig 4 & fig 5). And yes, it has some heft as the base has a large hunk of cast iron in it. Will admit I spent $1.24 for the sink strainer that sacrificed itself to become the grill ala D-104.

The self-satisfaction of building your own gear and accessories is one of the rewards of this hobby, can’t buy that in a store. And repurposing someone’s trash into something useful is a plus.

Keep the soldering iron hot.

73’s

Paul KL7FLR

Wasilla, Alaska

PS JoAnn’s is one of my favorite places for finding useful materials.

Please Help This Guy

From time to time we use the SolderSmoke blog and podcast to try to help those in need.  We have close ties to the Dominican Republic and often become aware of people who are in real trouble in that country.  Here is case of a man who really needs some assistance.  Please take a look and consider helping him out.
https://www.gofundme.com/ramons-medical-treatment

More on K0EOO's Amazing Homebrew SSB Rig

Hello Bill,

The rig was my own design based on an article by Guy Gillet, ON5FE, published in QST, Jan 1970. (Editor's Note:  ON5FE's article also appears in the 1970 edition of the ARRL's book "Single Sideband for the Radio Amateur.") His article had some features I wanted and became the guts of the transceiver I finally came up with…  The rig took me some 2-4 years to complete mainly because I keep changing circuits and improving performance.  For example, I started with a 4 digit counter using nixie tubes and ended up with 7 digit 7 segment LED counter summing the BFO, VFO and HFO.  I also later added the keyer and CW audio filter and so on…..

Other than the outer cabinet from LMB, I did all the metal work complements of the metal shop at our lab at CDC’s advanced design lab.

Pictures show bottom with RF bottom plate installed and bottom view of RF section with plate removed.  Front panel and picture of top cover open showing the plugin PCB’s.  Cannot see the digital counter display board in any of the pictures.

Here are a couple pictures of the old girl.  I’ve added a description of the rigs features:

Features:

• Dual conversion, first IF tunable, second IF fixed
• RF clipping
• 7 digit readout of exact operating frequency (digital summation of BFO, VFO and HFO)
• All solid state except for 6146 and 12BY7 driver.
• RF gain is 0-60dB step attenuator on input
• Dual VFO’s for separate receive/transmit or transceiver A/B
• Modes are USB/LSB/CW
• Auto zeroing S-Meter
• Built in VOX and PTT
• Built in CW keyer and sidetone generator
• Built in CW audio bandwidth filter
• Built in Tune mode
• Built in RF Clipping lever control
• Built in keying to PTT external amplifier
• Output signals for SB-610 scope receive signal monitoring
• Output signal for SB-620 Scanalyzer panadapter
• Diode T/R switching through out the radio, no relays, totally silent TR switching

Well Bill, you opened Pandora’s box when you asked me for more details, hi, hi…  You can almost see the buttons popping off my vest as I reminisced the feature list…

Regards, Dennis, K0EOO

K0EOO: Homebrew SSB in 1974

It is not everyday that you get on 40 meters and run into a guy who has actually built a single sideband transceiver.  But that is what happened to me today.   I spoke to Dennis, K0EOO.  He  showed an unusual interest in my BITX DIGI-TIA.  He went on to explain that he had done some homebewing himself.  In the picture (from 1974), right next to his Vibroplex bug we see his homebrew,  80-10 meter,  dual conversion,  solid state (except for the 6146 final) SSB transceiver with digital readout.  Wow.  That's a beautiful rig.  

Off his right shoulder is a homebrew 700 watt amplifier using dual 4CX250s. And behind his left shoulder we see a homebrew tube-type receiver.

Note the look of pride and determination in OM's eyes.  You can just hear him saying it: "Rig here is homebrew."

More pictures of Dennis and his rigs (including some amazing vintage gear)  here:

https://qrz.com/db/K0EOO

http://www.isquare.com/millen/members/k0eoo.htm

http://www.vintagessb.net/k0eoo.htm

Thermatrons Al Fresco: W4GON's FB HB AM Rig

I was listening to 7290 kHz with my BITX this morning and I heard W4GON say his AM rig is homebrew.  So of course I fired up the DX-100 and the HQ-100 and gave Joel a call.  Conditions were terrible but we had some support from the radio gods.  

From Joel's QRZ.com page: "It uses a pair of 6L6s in Push-Pull Class AB1 high level plate and screen modulating a 6146. I still have a lot of work to do on this rig, like building an enclosure, but it works and I just couldn't help but getting on the air with it!"  

I think it is a thing of beauty. 

Let's Give Jason NT7S Some Support!

Most of us are using Jason's code and his Arduino Si5351 libraries.   We now have an opportunity to help him continue to come up with the innovations that keep things moving forward on our workbenches.  

Consider becoming a patron.   Learn more here:  

https://www.patreon.com/NT7S

Thanks for all you do Jason!  

"So You Want To Build?" Words of Wisdom from Pete Juliano

Everything on Pete's blog is worth reading, but this article was so good that I could not resist posting a link to it here. 

Tribal knowledge from a leader of the homebrew tribe: 

http://n6qw.blogspot.com/2017/08/a-new-line-of-transceivers-difx.html

AE7KI (VK2APG), FT8, and WAS on a BITX20

I've had several very nice conversations with Gerry AE7KI (aka VK2APG).  His Australian accent sets him apart from the other Tennessee stations.  Last time we talked Gerry mentioned having competed Worked All States with his BITX20 (below). Very cool.

Gerry also alerted me to a new digital mode created by Joe Taylor.  This one is called FT8.  Gerry is using it to good effect on the 6 meter band. Here is Peter Marks' initial reaction to FT8:

http://blog.marxy.org/2017/07/new-weak-signal-mode-ft8.html

As I type, there are 252 stations monitoring 6 meters for FT8 signals.   You can see a map displaying these stations here: 

https://pskreporter.info/pskmap.html

Yellow Fever! The Cold War Origins of Juliello

How could you miss them?  That yellow was bright!  Apparently you needed high visibility to cope with the looming danger of nuclear annihilation.  The operator in the ad is obviously calm in the face of Armageddon -- note the cigarette dangling from his lips. In this 1956 Gonset ad we can see the inspiration behind what -- many decades later -- has emerged as the avant-garde ham radio color scheme known as Juliello.  The roots of this aesthetic are clearly not in the psychedelic "Mellow Yellow" hippie era.  No, this color has harder, more flinty origins.

Pete Juliano is not the only one to embrace this look.   Podcast #198 elicited this response from our friend Armand WA1UQO: 

Pete:
Don't let that Meara guy give you a hard time over the yellow Rigs.  The last three of mine have been yellow and I'm happy to see I'm not the only one with good taste.  In the picture they are from top to bottom a 30M One Watter, a 20M One Watter and of course the BITX 40.  The 20M does have a Juliano Blue cover though to give it an extra bit of class!  As always, enjoyed the podcast.
Bill,  see you at Berryville?
73, Armand WA1UQO

SolderSmoke Podcast #198 - D-104, HW-8, Juliello, DIFX, Dishal, Baofeng, MAILBAG

Bill Breshears WC3K (SK)

SolderSmoke Podcast #198 is available. 

http://soldersmoke.com/soldersmoke198.mp3

29 July 2017

Sign on a beach store:  SHACK-TACULAR! 

Noticed that EB63 amp was getting hot. Why?  

TT2, Herring Aid5, Farhan's Key:  QRPp and CW!  See?

D-104 lore -- Reading from Bill Breshear's (WC3K) ER article

Astatic  crystal/ceramic element -- disappointingly flimsy

Electret-ing it.  The G-Spot (see picture above)

Walery KB2FIV sent crystal mic element and piezo buzzer (reverse for mic!) FB

HW-8 AF filter Center Frequency Problem.  IT'S TRUE!  Fixed!  Finally. 

Shack re-org at N2CQR

Got Steve Silverman's HP 8640B Sig gen on the bench.  Required reinforcement

Pete's new DIFX

LM373 rigs.  Perhaps with that CA3020 Pete sent me. Chips Ahoy! 

Juliano Yellow? Origins of Blue?  Juliello? Julionyx? 

HB Crystal Filter Capitulation? Don't give up Pete --  just dish the Dishal!

Ceramic VXOs?  K.P.S. Kang

Crystal testers by G7WKE and Dino KL0S.  Impressive. 

Antennas and BITX40 modules.  Antennas are important.

Bill's new Baofeng HT on 440.

Fixing my Sony SW7600GR

MAILBAG

Steve Silverman alerts us to NYC radio row now in the Bronx.

Tony G4WIF on the cover of SPRAT -- Getting the Don Cameron award. FB 

Armand WA1UQO points out that the Berryville hamfest is coming up... 

Thomas KK6AHT F4HDQ writes in. 

On the air with W8NSA

Juliello.  No. 

Ralph Baer -- Video Game Inventor

Thanks to Stephen G7VFY for alerting us to this very nice video.   Ralph Baer did pioneering work in video games.   It is fun to see him in his workshop. He obviously has a variant of The Knack.  Stephen hinted at a reference to "noodling" but I didn't hear it -- perhaps Stephen meant that the whole thing was about what we'd call noodling.  I found the box on his bench labeled "Wire Wrap Materials" kind of ominous -- remember our April 1 announcement about the launch of the new "Wire Wrap Rap" podcast?

I liked Ralph's summary comment about how these days he just has fun building things.

KC8WBK's Cakepan BITX40

I talked to Paul KC8WBK last night during the regular 7277 kHz Sunday night BITX gathering (7 pm local). I like his BITX enclosure.  Very practical and economical.  It provides ready access to the circuitry.  He also has nice enclosure for the microphone and push-to-talk switch. He has more info on his QRZ.com page. 

Einstein's Knack (for Refrigeration)

https://www.wired.com/story/einsteins-little-known-passion-project-a-refrigerator?google_editors_picks=true

Intuitive Repair of a Sony Shortwave Portable

A few years ago my wife got me this nice little Sony ICF-SW7600GR receiver.   On the front it proclaims that it is "AM DUAL CONVERSION" and "PLL SYNTHESIZED."   It has a BFO, and a filter of suitable width for SSB.  It also has a synchronous detector -- it generates an internal carrier that matches the frequency and phase of the carrier being transmitted by the SW broadcast (or ham AM) transmitter.  This helps overcome the selective fading that often plagues AM signals.  Sony advises switching to USB or LSB once the synchronous generator locks onto the carrier.  Pretty cool. 

The BFO is the reason I wanted this receiver. And wouldn't you know, when I dropped it,  it landed EXACTLY on the little BFO fine tune control pot.  It was as if the Radio Gods disliked all the fancy digi PLL synchronous IC circuitry.   

I tried without success to find the value of the destroyed pot.  Finally, last week I just decided to have a look in there to see if I could just figure it out. 

On the board I could see that the pot only connected at two places, so I figured it would be a varactor circuit on the BFO with one end of the pot to DC and the wiper to the varactor diode.  I figured I'd try a 10K pot. 

This seems to have been some good radio intuition.  It works.  I went with a small trimmer because it is less obtrusive and because once I set the BFO in the right spot, I think the de facto channelization of the 40 meter ham band will keep most of the SSB sigs in tune. And the Sony only tunes in 1 kHz increments. If necessary I can move the BFO a bit with a small screwdriver.  I just glued the trimmer pot onto the back of the receiver -- two wires covered by heat shrink run back into the circuitry. 

10k might be a bit too small.  Maybe 100k would be better?  As it is, I can move the BFO above and below the "zero beat" point, and I don't need more range. Mouser has a small trimmer pot with a tuning wheel that looks like it might fit, so I may try for a proper repair.