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Wednesday, November 22, 2017

iPhone Direct Conversion Receiver with Variable Ceramic Oscillator

A while back Bob N7SUR got us talking about winter projects.  Receivers.  Of course, Pete and I quickly went down different paths.  Pete is making great progress with lots of interesting digital circuitry.  He is going over to the dark side. Check it out here: 

I went with simplicity.  Extreme simplicity.  Direct Conversion (thanks Wes!).  Discrete components.  No chips.  Analog Oscillator.  40 meters -- monoband.   

There it is.  You can click on the picture to make it larger. Here is an outline of the circuitry: 

-- Single tuned circuit bandpass filter preceded by a simple pot that serves as a gain control. 
-- JFET RF amp
-- Singly balanced passive mixer inspired by F5LVG's RX-20 in SPRAT 100.  For the coil I used one of the many trifilar toroids that Farhan gave me. 
-- The local oscillator is the coolest stage.  I used a 7.37 MHz ceramic resonator and a circuit inspired by Miguel PY2OHH. With a polivaricon I can tune the entire 40 meter band. I put a reduction drive int here to make tuning easier. 
-- The AF amp is an op-amp free design.  It works well into ear buds or into a computer speaker. 
-- Perhaps in an effort to catch the attention of the younger generation, I built it into an iPhone box.  

Please let me know if you spot any flaws in the circuit, or see any places where it might be improved. 

More to follow.   This prototype is now in the mail, en route to my nephew John Henry who will be testing it for me. 

Saturday, November 18, 2017

China and SETI: What Happens if China Makes First Contact?

Here is a really amazing article from The Atlantic.  It is very thought provoking.  Mind blowing.  Strongly recommended. 

You can read it here:

Or you can listen to a reading of it (like a podcast) here:

Thanks to Mike Rainey AA1TJ for alerting us to this. 

Friday, November 17, 2017

Jeff Murray's Grumpy Audio Guy from 40 meters

I've talked to this guy several times.  He usually waits until I'm testing a new rig.

I'm sure Pete has worked him too.  

Saturday, November 11, 2017

Amazing Homebrew/Boatanchors QSOs on 40 --Six solder melters in a row!

After a day of happy tinkering with the Direct Conversion receiver I've been working on, I turned off the soldering iron and got on 40 meter SSB with my BITX Digi-Tia. 

First -- Steve W4IJ came back to my CQ.  Steve is a boatanchor enthusiast and has written for Electric Radio magazine.  FB. 
W4IJ Boatanchors
When Steve signed off, I got into a contact with Pete W8NBO.  We had spoken before and he had told me of a homebrew transmitter he'd built as a kid.  This time I asked for details: It was a 6AG7 oscillator to a 6L6 amplifier.  He ran it with an S38 (brave man!).  He described what must have been a very painful effort to hack (literally) the needed holes in the transmitter chassis using just a spike, a hammer and a file.  I told him this brought back my memories of similarly painful chassis work (mine was for a power supply for a Heath HW-32A).

At this point we were joined by Arnie, W2HDI.   Arnie's rig is in Stowe Vermont, but he was running it remote from the South of France where he and his wife were celebrating their 50th wedding anniversary.  Arnie shared with us memories of similar chassis pain -- his were related to an external modulator that he built for a DX-40. I think he said that all he had was a hole punch and a file.  Oh, the humanity! 

Then Al W8VR joined the conversation.  Al said that he's been in the game so long that his early rigs were built using cigar boxes as chassis.  I pointed to a connection:  I noted that my BITX rigs are enclosed in what could be considered cigar boxes.  Al's QRZ page picture has a magnificent AM rack rig that he said was actually built twice.  There is also an HRO-60 in the picture.  FB. Check it all out at Al's web site.  Click on the mic for the write ups, the key for the pictures.

Then Dennis K0EOO called in.  Holy Cow!   Dennis and I spoke not long ago.  You may recall my enthusiastic write up of his beautiful 1974 SSB rig: 

This was almost too much.  Rarely will you spontaneously come across so many hams who have melted so much solder.  FB. 

Icing on the cake:   When I returned to the bench, I fired up the DC receiver and heard Mike KN4EAR talking about his BITX40.  I switched to the Digi-Tia and gave Mike a call.  He reports making many contacts with his rig. FB. 


Wednesday, November 8, 2017

Beautiful QSL by Jeff Murray K1NSS

Here's a reminder of the amazing art work of Jeff Murray K1NSS. 
You can have him draw a QSL for you:   Go here:

Jeff writes: 
Well, I got as far as high school intermediate algebra and then I saw a squirrel.
Thank goodness others like Ken N2WWD were paying attention and went on to surf gravity's rainbow of flight dynamics, all in a day's work and play for rocket scientists. Tandem surfing and professional activities somewhat aside, Ken is also actively involved with ARISS, i.e. Amateur Radio on the International Space Station, the group guiding ham radio operations aboard ISS. So Kelvin cool to work with Ken on this New One, with Ken cooking up a special Easter Egg for all you galactic hitchhikers!

What might I draw with you?

Monday, November 6, 2017

Jan's FB Slovakian SMD TIA Boards


I have put up my SMD version of the TIA amplifier boards online, in case
someone wants it. The files are here:

and direct OSHPark order link:

73!, Jan

Saturday, November 4, 2017

Termination Insensitive Amp Boards from VU3ZMV -- Eagle Files


Here are the eagle file data for the TIA, that I love to use as incorporated in Farhan's ubitx.

The TIA , I tried to realise two such on a double sided pcb measuring less than an inch.
 It mounts one TIA on each side.  I suppose one could simply homebrew.
It has provision for 5 pin berg (male right angle) and would be easy to plug into the main board. We may not need PTH except the connector. We can use bare pins soldering on either side.
Here are the eagle files I created.

Sarma's TIA Board

Sarma's TIA schematic


The Ham-Radio Thermatron Roots of Silicon Valley

Hack-A-Day had an excellent piece on tubes and Silicon Valley this week.  Makes me want to get the book "Secret History of Silicon Valley." 

Note above the Klystron prototype mounted on a wooden board.   These guys clearly had THE KNACK. 

Friday, November 3, 2017

Another Source for BITX Amp Boards - AG4ZP

Thanks for sharing (the infor on the modular BITX boards). I actually had a similar idea a number of years ago and designed a small PCB for the ubiquitous BITX amplifier design. I have the project shared on OSH Park and you can get three of them shipped for $5.

The project is shared here.
Ryan AG4ZP

Tuesday, October 31, 2017

Cliff Stoll on Software, Snake Oil, and the Creation of Real Things

"I guess today's experimenters build things in software, without ever touching a soldering iron. The hocus pocus is inside the program.  It's cleaner this way -- nothing to burn or zap, and you don't need a voltmeter... What happened to home-brewed and breadboarded circuitry? Where's the joy of mechanics and electricity, the creation of real things?  Who are the tinkerers with a lust for electronics?"   

From "Silicon Snake Oil"  1995 by Cliff Stoll  

Monday, October 30, 2017

Modular BITX Boards

Sunday, October 29, 2017

Ron Gang, 4X1MK on "QSO Today" Podcast: Knack Story, Satellites, Quads, Philosophy

Wow, Eric Guth's interview with Ron Gang 4X1MK really resonated with me: 

-- Asked about how he got is start in radio, Ron went back further than many of us do in response to this question.  He cited his early experiments with "two tin cans and a string." Yes, of course!  I'd forgotten all about it, but in retrospect this might have been a very early indication of THE KNACK.  (I'll bet many of our readers were also active on the String and Can band.) 

-- Ron used a DX-100.  FB. 

-- Ron was active on the satellites.  In his voice you can hear the joy and the burst of enthusiasm that resulted from those early satellite contacts.  He also mentions the untimely demise of Oscar 13.  Bummer. 

-- Ron was the Israel correspondent for 73 Magazine.  I held a similar position in Dominican Republic.  My friend David Cowhig was at the same time correspondent from Okinawa, Japan.  We should have a reunion of "73 Magazine Hambassadors."

-- Ron mentions John Tait EI7BA.  John was a regular contact of mine when I was in the Azores.  He appears in the SolderSmoke book.  He was the one who introduced me to an important Irish accolade:  John told me that WD-40 is "the Pope's pee." 

-- Toward the end, Ron discusses the wonder of ham radio conversations, and provides a good suggestion on how to get beyond the all-to-common "hello-59-goodbye" contacts. 

Ron's comments on the spiritual or philosophical aspects of the hobby were just the thing for a quiet Sunday morning. 

Thanks to Eric and to Ron for a great interview.   
Listen here:

Saturday, October 28, 2017

BITX40 Featured in "Nuts and Volts"

Congratulations to Steve Jackson and to "Nuts and Volts" for putting out a very nice article on the BITX40 transceiver.   Steve did a great job in describing the origins of the BITX, and in explaining that Farhan's intent is to encourage experimentation and tinkering.  Pete and I had pitched a similar article to a major ham radio magazine  but sadly they were not interested.  Three cheers for "Nuts and Volts."  I'm thinking about subscribing. 

I know many of you will wince when you see Steve's unshielded mic cord lying right next to the front panel antenna connector, but please don't freak out about this -- in the article you will see that Steve acknowledges that the antenna connector would have been better placed on the back of the box.  That's an example of the educational value of the BITX40 -- live and learn.  Even with the connector like this, Steve was making many contacts. 

The "Nuts and Volts" website very kindly let me read the entire article without a subscription. 

Try here and click on the blue "digital edition" box:

Or try going directly here:

Thursday, October 26, 2017

Pete's Simple-ceiver -- Al Fresco Success

N6QW's Simple-ceiver design is being replicated far and wide.  Above you can see PA3GUP's beautiful rig in its "Al Fresco" stage of development.  For much more of this -- including a cool video of Pete's rig in action -- go to Pete's blog: 

Tuesday, October 24, 2017

630 Meter DX from Wasilla, Alaska

Kl7L's 600m Part 5 station
Hi Bill - It's been a few years and I'm sort of glad my global wanderings have been curtailed to a point and I'm now based out of Alaska and via a couple of call signs (KL1X KL7UK etc) have ended up with KL7L. I still travel with the Oil Company but no China on the horizon.

I had a chuckle when you and Pete mentioned the new 630 and 2200m bands - and the real estate requirements - Well, I've been active with the experimental callsigns since 2003 and very glad we have finally got the bands - so a small form to fill out on the UTC web site and a 30 days wait to check you are not within 1Km radii of the co channel PLC on Trunk power lines, if no "disapprove" away we go - and I and many have! 

Just turn off all those nasty dimmers, LED lights and SMPSU wallwarts - plonk your radio on 474.2kHz USB and decode using WSPR or JT9 and I think youll be surprised on what you can hear even on a short typical 80m or topband wire or so.  There a lot of activity all around you

The station for both band is homebrew soldersmoke heaven - transverter/PA and filters/Couplers/Phase meters etc with only my ol' TS850 doing the prime driving, or a Hans  Summers U3S.

Size does matter - but my best RX for both bands is a 2ft long active probe up a pine tree, that's all - and some 300ft of RG6, and the Tx antenna is a 60ft high  Marconi or more over an inverted L with a 3 wire top cap all nested in the Birch forest - loads or radials but still very lossy in the Summer - nothing special here - Of course with the QRP per se we have to use CW or digital modes mostly but DX can be done - after all my closest active neighbor on 2200/630m is over 2000Kms away!

So, for the first time I sparked up on JT9 on 630m this early morning and first blood to QSO with VK4YB @ 5W EIRP!

 Not bad for a first qso on what is a fairly typical back yard antenna - so, there is hope and many people appear to be putting transcontinental signals out this power, so everyone is on the same playing field - just the ground and location and latitude will change things! It tends to be more flaky, lossy and geo/solar events tend to hit us hard up here compared with say Seattle.

On 2200m TX its a loop of thick wire hanging in the trees - literally 500ft circumference and a beefy coupler to deal with the 50A or so of antenna current to make the 1W ERP or so - still its getting out OK and again should be putting signals over the Pole to EU and across the Pacific as it becomes more and more dark up here.

I'm now caught up with past Soldersmoke pod casts and thanks to you and Pete for making me smile

Take care

Laurence KL7L  aka G4DMA et al
Wasilla Alaska 23rd Oct 2017

Monday, October 23, 2017

Woz with Soldering Iron; Wooden Enclosures for Electronics (Video)

The Woz scared me for a second -- I tought he was going to leave a hot iron on the desk amidst paper and other flamable items.  But no -- he put the soldering iron in its holder. 

Later we hear Woz talking about the need to update schematic diagrams.  And I was esepcially taken by the use of wooden enclosures for electronic projects.  My BITX rigs have followed the Apple example. 

Sunday, October 22, 2017

Cliff Stoll -- K7TA -- Has THE KNACK. And a GREAT NOVA Video

Hack-A-Day had a piece on Cliff Stoll of  "The Cuckoo's Egg" and "Silicon Snake Oil" fame.  I read these books years ago.  I included a quote from Cliff on page 45 of the SolderSmoke book (the quote seemed to foreshadow my aversion to SDR). 

I didn't know that NOVA produced an hour-long program on Stoll's Cuckoo's Egg adventures.  It is really good.  Many of those involved play themselves in the video.  Very cool. See above. 

I checked Cliff's page.   We wrote several years ago that Cliff has THE KNACK.  Note below his preference for thermatrons and the affection for Heathkits.  Diagnosis confirmed. 


   Hi gang!   This is Cliff Stoll, K7TA
   Way back in the Jurassic, I was licensed as WN2PSX, in Buffalo NY.  Got my general ticket around 1967 as WB2PSX, and helped build ham radio stations at Hutch-Tech high school, University/Buffalo, and University of Arizona.   When I went to Tucson for grad school, I passed my extra ticket and snagged the call K7TA (back when this meant 20wpm cw).  I held a first-class commercial ticket, which let me engineer at WBFO radio, but I don't know if commercial licenses even exist anymore.
   I now live in Oakland California, and occasionally get on the cw lowbands with old heathkit gear ... just rebuilt my novice NC-270 receiver with filaments that glow in the dark.  Gotta restring my 40 meter dipole that came down in a windstorm.  
   You can guess that I'm pretty much retired.  Along the way, I've worked in FM radio, planetary physics, computing, writing, speaking, teaching, and math.  Best way to reach me is through my website
   Warm wishes to all -- 73's,

Info on Cliff's latest gig: 

Saturday, October 21, 2017

The First "Transistor Radio"

I'm a few days behind on this.  On October 18 Bob Crane pointed out that Garrison Keillor marked the anniversary of the broadcast band "transistor radio."   I had mine (a 1970s version), and it did indeed allow me to listen to that seditious rock music without parental interference. Looking around the shack, I still have items in use that have "Transistorized" as part of their product name (like my Lafayette Radio Electronics Transistorized DC Power Supply." 

Garrison (on October 18, 2017): 

It was on this day in 1954 that the first transistor radio appeared on the market.
Transistors were a big breakthrough in electronics — a new way to amplify signals. They replaced vacuum tubes, which were fragile, slow to warm up, and unreliable. During World War II, there was a big funding push to try to update vacuum tubes, since they were used in radio-controlled bombs but didn't work very well. A team of scientists at Bell Laboratories invented the first transistor technology in 1947. But the announcement didn't make much of an impact because transistors had limited use for everyday consumers — they were used mainly in military technology, telephone switching equipment, and hearing aids.
Several companies bought licenses from Bell, including Texas Instruments, who was bent on being the first to market with a transistor radio. Radios were mostly big, bulky devices that stayed in one place — usually in the living room — while the whole family gathered around to listen to programming. There were some portable radios made with vacuum tubes, but they were about the size of lunch boxes, they used heavy nonrechargeable batteries, they took a long time to start working while the tubes warmed up, and they were fragile. Texas Instruments was determined to create a radio that was small and portable, and to get it out for the Christmas shopping season. They produced the transistors, and they partnered with the Regency Division of Industrial Development Engineering Associates, who manufactured the actual radios. Their new radio, the Regency TR-1, turned on immediately, weighed half a pound, and could fit in your pocket. It cost $49.95, and more than 100,000 were sold.
Texas Instruments went on to pursue other projects, but a Japanese company called Tokyo Tsushin Kogyo decided to make transistor radios their main enterprise. They were concerned that their name was too difficult for an American audience to pronounce, so they decided to rebrand themselves with something simpler. They looked up the Latin word for sound, which was sonus. And they liked the term sonny boys — English slang that was used in Japan for exceptionally bright, promising boys. And so the company Sony was born. Soon transistor radios were cheap and prevalent.
With transistor radios, teenagers were able to listen to music out of their parents' earshot. This made possible the explosion of a new genre of American music: rock and roll.

Friday, October 20, 2017

The Quantum Indians

Beautiful video.  Strongly  recommended.

Thursday, October 19, 2017

Ham Radio, Dilbert, Dating, and the Baofeng Breakup

Was the young lady turned off by his obvious "appliance op" status? Was it the Baofeng?  Would he have fared better with a homebrew rig? 

Dilbert addressed the relationship between ham radio and success in the dating game: 

I blame Peter VK2EMU for this digression. 

Saturday, October 14, 2017

SolderSmoke Podcast #200! 17, Knack Nobel, QCX, 630, UHF, Fessenden, TROUBLESHOOTING

DL3AO 1950
SolderSmoke Podcast #200 -- TWO HUNDRED!!!!-- Is available

-- Old friends on 17 meters.  

-- Another Knack Nobel in Physics.  

-- Hans Summers' QCX transceiver:  $50 IS THE NEW 10 GRAND! 

-- New Bands!  630 and 2200 Meters.  BIG ANTENNAS! 

-- Nuke Powered QRP.  No joke! 

-- The Challenge of UHF.  Not for the faint of heart. 

-- Reginald Fessenden, Father of Phone. 

PETE'S BENCH REPORT:   The New Simple-ceiver.  Soon to be a Transceiver. 

BILL's BENCH REPORT:  Discrete, Direct Conversion, Ceramic Receiver in iPhone Box.  



DL3AO 1950

Tuesday, October 10, 2017

SPRAT -- The 007 Connection

The eagle eye of Brent KD0GLS spotted this frame in the 007 movie "Casino Royale."  
Wow -- I just knew those GQRP guys had to be much cooler than they seemed.  I guess there were some indications: They do seem to talk quite a bit about "Q".  There is that weird fondness for Parasets. I understand that several of the senior GQRPers drive Aston Martins.  And that Dobbs guy -- a kindly retired Anglican minister you say?  Really?  I can just hear him saying it:  "Dobbs, George Dobbs."  

Monday, October 9, 2017

DL1YC's Flat Moxon with Armstrong Rotation

DL1YC Moxon
I had a very nice contact on 17 meters yesterday with Jan DL1YC.  It was a rare Moxon-to-Moxon contact, with homebrew 17 meter Moxons on either end.  Jan's is a bit cooler than mine:   His is flat, without the "blownout umbrella" support that we see in mine (below) and in the Hex Beams.  Jans told me that he achieved this flatness by starting out with very long telescoping fishing poles -- he discarded the the thin portions of the pole and used only the more rigid pieces.  (I used 16 foot, 5 piece Shakespeare Wonderpoles from Amazon.) I think he also used thin wire for the elements.  The crossbar that you see in the picture above is there to support a balun at the feed point -- without the cross bar the balun and the feedline would cause the balun to droop. 

I couldn't resist a little front to back testing.   Jan's antenna does not have a rotator -- he used the "Armstrong" method of antenna pointing.  I didn't want to make him go outside to spin the thing around by hand, so I just turned mine and asked him to take note of the difference front to back.  He saw 3 S units.  18 db.  Not bad.   

Jan said his antenna weighs about 8 pounds -- mine is very similar at 9 pounds.  Jan expressed some concern about UV deterioration of the fishing pole fiberglass.  Mine has been up there three years without any problems.  

Like me, Jan had considered "nesting" an element for another ban (perhaps 20 or 12) but -- like me-- had concluded that this would be too difficult. 

N2CQR Moxon

Sunday, October 8, 2017

A Direct Conversion iPhone!

Well, really a DC receiver in an iPhone box.

I think the Apple iPhone boxes have great potential as project enclosures.  They are cardboard, but they are very rigid and solid.   I decided to use them for a Direct Conversion receiver project I've had in mind.  

This is a 40 meter DC receiver.  No chips.  Ceramic resonator VXO tuned by a varactor diode. 9V battery as the power source.  Ear buds as the transducer.  Passive, two diode, singly balanced detector.  It sounds great -- so great that I may have to add a gain control. 

The nice fit is no coincidence -- I cut the board so it would fit in the iPhone box.  

Take a look at that top cover.  It is all, well, empty.   I could put another board in there, right?  Maybe a balanced modulator,  a mic amp and an RF amplifier.  Then this thing would be a Double Sideband transceiver.  We could even make use of the little microphone that comes with most of the ear buds.  

I'm thinking that this might be the kind of project that people would like to take on this winter.  Build the VXO first.  Then the AF amp.  Then the product detector and front end. At that point you've built a receiver.  For extra credit you could go on to the transmitter.  No need to use Apple boxes (but they are cool...)  I will try to get the schematic done soon.  My nephew John Henry will test the prototype. 

Saturday, October 7, 2017

IZ7VHF's Video on on Hans Summers' QCX Rig, and a Video from Hans

Thanks to W8SX for alerting me to this. 

There is a lot of good stuff on Roberto's site.  He obviously has THE KNACK.

Hans himself has a less detailed video on the rig:

Friday, October 6, 2017

VE3BOF's Regens and DC Receivers

Hi Bill:

This is Clark, VE3BOF, in Hensall, Ontario, Canada.
Hensall is located in southwestern Ontario, north of London and a 2  
hour drive west of Toronto.

Last Sunday night, 2017-10-01, I tuned in to 7277 kHz to listen to  
the BitX40 net. I heard you and 2 or 3 others.
Your signal was 5-7, perfectly readable.

The receiver I was using is a modified version of the WBR receiver.
It is still on the piece of chipboard that I mounted all the modules  
onto.  It's an excellent little regenerative receiver.

In the same state of incompleteness, is a modified version of the  
Easy Receiver (QRP Kits) direct-conversion receiver,
I use this receiver for the CW end of the 40M band.

Both receivers have been fitted with 10-turn pots for easy tuning,  
and also lcd frequency counters for displays.

I'm a former Motorola Communications tech, and used to maintain the  
radio systems of District 6 of the Ontario Provincial Police and our Ministry 
of Health emergency services radio system.

Being retired now, I have more time to check Soldersmoke every day  
and listen to your
conversations with Pete, N6QW.

Thank you for very interesting and worthwhile QRP information and  

Clark Forrest, VE3BOF

Wednesday, October 4, 2017

ANOTHER Nobel Prize Winner with THE KNACK

When I heard that the guys who ran the LIGO gravitation wave experiment won this year's Nobel Prize for physics, something told me that at least one of those involved in this historic detection of weak distant signals would have THE KNACK.  It did not take me long to confirm this.  Rainer Weiss (above) definitely has had the THE KNACK all his life. And what an interesting life it is.  Check it out:

Knackish excerpts: 

The family soon had to flee again, when U.K. Prime Minister Neville Chamberlain signed an accord ceding parts of Czechoslovakia to Germany. They heard the news on the night of 30 September 1938, while on vacation in the Tatra Mountains in Slovakia. As Chamberlain’s address blared from the hotel’s massive radio, 6-year-old Rainer stared in fascination at the glowing array of vacuum tubes inside the cabinet. The hotel emptied overnight as people fled to Prague.

As a teenager, Weiss developed two passions: classical music and electronics. Snapping up army surplus parts, he repaired radios out of his bedroom. He even made a deal with the local toughs: If they left him alone as he lugged radios to and from the subway, he’d fix theirs for free. “They would steal things and I would have to fix them,” he says. “It wasn’t a good deal.”

Weiss was drawn to tinkering partly as a reaction to his family’s cerebral atmosphere. “This is a German-refugee kid with very self-consciously cultured parents, and he’s rebelling against them by doing things with his hands,” Benjamin says. “But he’s surely not rejecting doing things with his head.”

He applied to MIT to study electrical engineering so that he could solve a problem in hi-fi—how to suppress the hiss made by the shellac records of the day. But electrical engineering courses disappointed him, as they focused more on power plants than on hi-fi. So Weiss switched to physics—the major that had, he says, the fewest requirements.

Tuesday, October 3, 2017

The Homebrew Receivers of F5LVG

I came across OM F5LVG's work in SPRAT.  He has a wonderful website -- it is in French, but Google Chrome translates is quite nicely.

From the site's introduction: 

This site is dedicated to the construction and understanding of radio receivers. If you have dreamed of hearing a radio station with a receiver that you have built yourself, this site is for you.  These are essentially direct conversion receivers and modern feedback detectors using only semiconductors, except for retrofitting. The described stations will accommodate amplitude modulation, single sideband (SSB) and telegraphy.
Besides these receivers several articles are devoted to LC oscillators. In particular, an extremely simple original stabilizing device is described.
Similarly, a simple frequency meter is described.
The joy of reception using a homebrew receiver is intense. May this site help you find this joy. Do not hesitate to join the amateur community.

Monday, October 2, 2017

TRGHS: I Can Hear the Roosters of Boa Vista

At the instigation of  Bob N7SUR I've been working on a simple, easy-to-reproduce Direct Conversion receiver for 40 meters. I'm building this for my nephew John Henry,  and I'm hoping this will be a circuit that others can use to break into the ELITE corp of successful ham receiver builders. Coincidentally Joh in Freiburg Germany is working on a very similar project -- we have been comparing notes. 

At first I used an FET detector described by Miguel PY2OHH.  It worked, but at night the AM detection of powerful shortwave broadcast stations drowned out the amateur signals.  So Joh and I started to explore detectors that would eliminate this problem.  I went with a version of one described in SPRAT by F5LVG ( "The RX-20 Receiver"- see below).  Very simple:  A transformer to two back-to-back diodes with a 1K pot to balance the signal from the VFO.  OM Olivier used a very, very cool transformer: he took two small, molded chokes and simply glued them together!  22uH choke as the primary, 100uH choke as the secondary. I went with one of the toroidal transformers that Farhan left me when he visited in May. 

 I'm using a varactor-controlled ceramic resonator VXO  (no Si5351 in this one!) and a non-IC AF amp designed for use with ear buds (the world is awash in ear buds).  It is a "singly balanced" design with the incoming RF signal being the one "balanced out" in the detector.  

Last night the receiver passed the AM breakthrough test.  The SW broadcast monsters were balanced out and kept at bay. 

This morning the receiver passed The Boa Vista Rooster Detection Test.   I fired up the receiver and heard an operator speaking Spanish with a Brazilian accent.   When I heard the rooster crowing in the background I knew it was Helio PV8AL from Boa Vista Brazil.  TRGHS -- this little receiver is a winner.  

I'll try to post a schematic soon.  

And hey -- look at what wonderful IBEW (International Brotherhood of Electronic Wizards) project this is:   Instigation and inspiration from Oregon.  Some design ideas from Brazil.  A French detector circuit described in a British QRP magazine. A transformer from India.   A collaborator in Germany.    And finally, the rooster of Boa Vista.    

Let's not forget Wes Hayward W7ZOI for bringing back (in 1968!) the neglected Direct Conversion idea.
Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column