REPRIEVE! SolderSmoke Saved by a Loophole!

First, let me thank the many, many MANY, loyal listeners from around the world who wrote in with expressions of support and sympathy.  Special thanks to our UK listeners who were notable in their indignation for they saw as a blatant example of US litigiousness "gone mad."  One loyal British listener went so far as to pledge to immediately end his patronage of the Birmingham Vaping business known as SodderSmoke.  We found this quite, well, suprising.   But we were chuffed, nonetheless.  Thanks OM! 

The expressions of concern were really quite touching.  One listener asked if he should  -- in an effort to keep us out of hot water -- destroy his SolderSmoke coffee mug.  With fans like that, well, what can I say?  

In responding to the legal crisis, our listeners displayed ASTOUNDING creativity in their crafting of alternative names for the podcast.   

Buck seems to have a real "knack" for name-smithing. He wrote: 
The easiest would be Solder Haze - it's a simple scan & replace.  But

if the trademark trolls grabbed 'haze' too...

Some other ideas:

Eutectic Point

The Solder Wick Chronicles

Sixty-Forty

PbSn

The Joy of Soldering

Fahrenheit 368

John suggested the rather toxic  "LeadVapors," but we feared that that one might lead to even more trouble, perhaps even with the EPA.  (But, no, wait -- no worries there!) 

Gary suggested SolderSuckers.   I briefly thought of the many people who wrote in (see above) but concluded that that one just sucked.  No. 

A number of listeners suggested legal counterattacks and fund-raising effots.  (We did get one unsolicited donation!)   One fellow suggested fighting fire with fire by having us trademark the phrase "Chicks dig it" and then just letting the money roll in. 

One devoted radio amateur said that he "informed his club and launched a letter writing campaign."  Thanks OM!  Keep those cards and letters going... 

There were, unfortunately, many disparaging comments about California, and "pot-heads," and "California pot heads."  But hey, Dudes...  they don't mind.  They are not going to let you harsh their mellows. 

Stewart tried to claim that there is some sort of UK rule that says that things like this can't be carried on past noon local time in Britain.  Ha! I said.  We are no longer bound by Imperial edicts.  

Similarly, Peter in Australia complained that the story reached him on April 2, rendering it null and void.  Sorry Peter, these are UTC operations my friend.  Time to wake up and join the rest of the world!

Well, let me get to the point:   The beloved name of our podcast and blog has been saved by a loophole.  You see, any legal challenges of this nature launched and announced on April 1st of each year are HIGHLY likely to be found, on even casual examination, to be be null, void, and totally bogus. 

So no, 

-- PETE'S COMPUTER WAS NOT SEIZED BY A COURT ORDER. 

-- THE CALIFORNIA MARIJUANA INDUSTRY IS NOT PLANNING ON MARKETING SOLDER-SCENTED WEED. 

-- THERE IS NO BIRMINGHAM COMPANY CALLED "SodderSmoke" (JUST THINK OF THE TRANSLATION!) 

-- WE ARE NOT BEING SUED FOR TRADEMARK VIOLATION BY AN EVIL MARIJUANA-VAPING JUGGERNAUT.  

But we thank you for your support.  And, to make it official:  APRIL FOOL!  73  Bill 

NO MORE SMOKE: Lawsuit Leads to Podcast Changes

We mentioned on the last podcast that we had some difficulties that led to a long delay between Podcast #202 and #203.   We couldn't go into detail, and we are still somewhat limited as to what we can say, but we thought that today we should bring you all as up-to-speed as we can with what has been going on.  

First, an apology.  Some of what we told you was, in retrospect, kind of misleading.  Pete's computer didn't really crash.  Sure, he did have to reconstruct a lot of files, but his original computer was just fine.  The problem was that it had been taken by court order as part of the legal mess we find ourselves in.   

Here is the deal:  We got hit with a "violation of trademark" lawsuit.  It seems that one of the new agricultural industries that has sprung up recently in California has taken a very aggressive legal stance in protecting their "rights."  Part of this effort is a proactive filing for trademark protection for any product name that could in the future be related to their product.   So apparently anything with "smoke" in the name was scooped up by them.  They also claim to forsee the possibility of a "solder-scented recreational product." We also suspect they are in cohoots  with the new electronic cigarette "vaping" industry.   We  have heard that they are working with a "vaping" company in Birmingham, England that calls itself "SodderSmoke."  (As you may have heard, the word has a different connotation in the UK.)  They are using this British Vaping thing to bolster their claim that we are violating their trademark.  

Pete feels terrible about all of this.  The fact that he is located in California was what allowed the LA lawyers to take us to court in that state.  And we have been advised that we do not have much of a chance in this matter.  You see, marijuana has become a very important product in Pete's state. And "vaping" with e-cigarettes is also very big out there.  So there is big money and big cultural forces behind this effort.  We a tiny small fish caught in the net of big new industries.  

Pete wants to fight this (you know how he is) but I think we will have to just give in and move on.  Look, STARTING TODAY they are threatening to sue us for ONE MILLION DOLLARS every instance in which we use name of the podcast that you have all come to love so much.  I am scrambling to expunge the title from all the blog files.  Just look at the header on the top of this blog page. 

So at this point we find ourselves in search of a new name.  We turn to you, our loyal listeners, for ideas.  We hope to come up with something that will remind people of what we once were, of the good times we had under the old name.  Please send us your suggestion.  PLEASE DO NOT use the e-mail address that has the old name in it.  That would just make the lawyers and the "farmers" rich.   Instead, send your suggestions to n2cqr@yahoo.com

Bill and Pete

  

Yet Another Household Item Useful to Homebrewers: Toilet Bowl Cleaner for PC Board Fabrication

We have already been using Desitin ointment for heat sink compound, kitchen breadboards for radio breadboards, Scotchbrite pads for polishing, nail polish varnish for toroidal core coating and Olive oil as a field-expedient lubricant. (Am I forgetting anything?)   But I must say I was a bit taken aback by KV4QB's mention of his innovative use of the dilute hydrochloric acid in toilet bowl cleaners in his PC board fabrication process.   Good one DuWayne!   Eric Guth went the extra mile be suggesting a recycling of the liquid. 

This was a really interesting QSO Today interview.  Listen here: 

https://www.qsotoday.com/podcasts/KV4QB

SolderSmoke Podcast #203 Winter, Transceivers, Antennas, DC RX, uBITX, Mixers, 'fests, MAILBAG

N6QW in 1959. Building an SSB transceiver

SolderSmoke Pocast #203 is (FINALLY!) available: 

http://soldersmoke.com/soldersmoke203.mp3

24 March 2018

--The reasons for our delay. 
Winter, Computers, College, Family Trees, Lawyers....

-- Winterfest 2018 
-- Pete launches 2018    THE YEAR OF THE TRANSCEIVER
    http://n6qw.blogspot.com/
-- SDR -  Satan's Digital Radio?  
-- Direct Conversion Receiver Projects
-- Mixer Musings 
-- A Thailand Troubleshoot 
-- Nor'Easter knocks out Bill's Moxon -- An appliance replacement? 
-- Homebrew Electret Mics.  Seriously.  
-- uBITX Build with Rogier
-- Civilized Crystal Testing
-- Baofeng! 
-- DRAGNET

-- MAILBAG
KD4PBJ's REGEN 
N6ORS's SDR rig
Mike Rainey's DX-100

Haunted by Hallicrafters At Winterfest

I was on the verge of not going to the Vienna Wireless Society's Winterfest Hamfest this year.   We had just returned from a long trip.  I was tired.  Armand WA1UQO bailed due to a family obligation. But, since this is about the only hamfest that regularly attend, and because it is only about 5 miles down the road, I went.  

As soon as I got there I started wondering if I should have stayed home.  Here's why:  Hallicrafter S-38s.   Just about everywhere I turned, there were S-38s.  I had never seen so many of these EVIL  AC/DC trandformerless widow-makers.  I watched in horror as innocent hams reached into their wallets and bought these little monsters.  "Does it work?" asked one victim. "Well," said the seller, "it hums like crazy when you turn it on."  Yea, I'll bet it does.  (The guy bought it.) 

It was kind of a Hallicrafters day.  I even saw an Hallicrafters TV!  See above. 

Nothing big followed me home.   I got a couple of nice variable caps (one with a reduction drive).  A Radio Shack speaker.   Some coax.  A project box of BITX40 size.   A Weller soldering gun  slightly less beat up than the one I've had since age 13. 

I got to meet Richard Choy of Midway Electronics.  He has a business out in the Shenandoah Valley and is selling a neat little 2 watt CW transceiver kit.  Go to midwayelecrronics.us/qrp for more info. 

Oh yea, I got a kick out of this ENORMOUS BFO.  I almost bought it for Pete (who is so fond of tiny little oscillators).  This is a real Boatanchor BFO.  I wonder how many Si5351s you could put in that box? 

Thanks to VWS for putting on the 'fest.  In spite of the S-38s, I had fun.  

WA1UQO's Discrete Ceramic DC Receiver

Armand writes: 

The attached picture is your DC receiver. A little tweaking left to do as the range right now is ~ 7.44Mhz to 7.032Mhz. I used one of Farhan's trifillars and a couple of air coils that you gave me last year.  Listening to the Wisconsin QSO party as I type. 

FB Armand!  The receiver looks great.  I hope others will follow your lead and build this simple little receiver for 40. 

Homebrew Your Own Electret Microphones

Don't be such a microphone appliance operator.  Whip up some of your own electret material and turn it into a mic.  Imagine how the audio adjustment guys will react when you tell them you are using a special, tailor-made,  homebrew electret material that gives added PRESENCE and BRIGHTNESS and SPARKLE.  Wow.  Minds will be blown.  A cottage industry could be launched.  

I realize that I tried to fool you guys with a bogus story about making your own Rochelle Salt mics using Tartar sauce.   But on this one, I'm not kidding.  Check out Hack-A-Day's excellent article: 

https://hackaday.com/2018/03/07/a-bit-more-than-a-microphone-the-electret-story/

Great Video on Crystal Motional Parameter Measurement

Who out there can save us from further Dishal distress?  Who has one of these fantastic bits of old test gear and is willing to donate it to the cause of accurate filter building?  

Thanks to Tore LB4RG for alerting us to this gem.  

Moxon Destroyed

The north-east region of the U.S.  is experiencing a very strong winter storm.  These storms are called "Nor-Easters"- that describes their track up the coast.   Here, we had wind gusts at 71 mph -- that was around what we had with Hurricane Sandy.  But no rain or snow down here -- it is a different story in New England. 

I was on the air, having a nice chat with Ivo OP2A on 17 when suddenly my SWR went way up.  I knew immediately what had happened.  I stepped outside and saw what you see above. 

Oh well, we had a good run.  It went up there on July 20, 2014.  Not bad for some fiberglass poles from Amazon, some scrap lumber and some wire from Steve Silverman (thanks Steve).  

To tell you the truth I was kind of hoping this would happen.  I'll replace it with a Moxon or a Hex that covers at least 20 and 17.   

N6ORS and "Satan's Digital Radio"

Hey Bill,

I just finished testing the new rig.  Better sit down for this......
Its an SDR (Satan's Digital Radio). Actually its an estension of an
earlier experiment You might remember the 'Franken SDR". The Franken sdr

worked so well I thought I would make a companion for it and built a QSE 

(quadrature sampling exciter) and an amplifier chain to go with it. The rig
used G3PLX's fantastic SDRTX software for the transmit and DB0JBJ's
wonderful HDSDR software for receiving. The original idea was to make
a small rig for Digital comms, but I decided to add a Mic for voice, also
there is a 'Hardware" audio Phaser already in the building stages 

(you can calm down now).

A few specs. The RX is fantastic , -135 noise floor and the audio is
so clean that it copies wspr signals to -33db. The transmit is 

12 watts and the phasing audio sounds so nice that my wife says 

"thats your terrible voice exactly."So if you catch me on Sunday night

 and i dont sound 'yellowee' enough and you justdont like that 

no-crystal-filter sound just say  "Hey , Dont phase me bro"

See Ya on the bands,
73
Keith N6ORS

Dragnet Goes After TV Repairmen in 1951

Detective Friday goes after a vicious new kind of crime:  Crooked TV repairmen who overcharge their customers.  These monsters unnecessarily replace (or say they do!) transformers, when all that is needed is a new 5U4 tube.  Oh, the humanity!   

And the reporter they were working with pretended to be a salesman for a new company dealing in rosin-core solder!   

No kidding.  I really thought this was a joke.  They were serious.  Just click on the video above to listen.  

Or scroll forward to the 1:32:59 point on this link.  Lots of tube talk.  This one's for you Grayson!  https://wamu.org/story/18/02/20/big-broadcast-feb-25-2018/

Soldering Fingers (and SWR Bridges) in Norway

Tore Bonderudtåjet LB4RG tells us that he is a SolderSmoke listener, and that the old tradition of hams soldering their fingers together continues to be practiced in Norway.   Here are some pictures of his latest efforts.  This is an SWR bridge project.  Thanks Tore!  Careful with the fingers OM! 

N8NM's "20 Dollar Bill" DC Receiver

Steve N8NM wrote: 

I call it "The $20 Bill" because it contains about $20 in junkbox parts and complies with Bill's discreet component, hardware defined radio ethos.

73 - Steve N8NM

https://n8nmsteve.blogspot.com/2018/02/spontaneous-construction-20-bill-or-oh.html

I replied:  

Excellent Steve.   Very nice.   

Your post caused me to fire up my DC RX -- I was listening on 40 earlier today.  I think the world needs MORE 40 meter direct conversion receivers.  

Too bad about the regulator IC chip.  We need to get you an 8 volt Zener so that you can bring that receiver into a state of discrete component purity.  

DISCRETE HDR FOREVER!  

73  Bill N2CQR 

A Wonderful Troubleshooting Story -- Thailand, Mixers, a Simpson 260, Microwaves, and some Black Tape

My old friend was really fortunate to have had such a good Staff Sergeant instructor at Signal School, someone for whom the mixer trig was obviously not enough.  And our old friend obviously also benefitted greatly from having had a dad who set him up with a Simpson 260 and some handmade experimental glass diodes. Wow.  It all came together with some black tape in Thailand... 

Bill,

Enjoyed your latest blog. I remember your asking about mixers years 

ago.  I received much the same explanation from a Staff Sergeant 

instructor at Ft. Monmouth in 1967.  His example was a mixer with 

diodes, noting the need to have them forward biased by the LO supply.  

We worked out much the same waveforms as shown in your Blog and 

the concept became part of my 'intuitive' knowledge.

A few years later I was fighting 120hz hum on the baseband of an IWCS 

microwave system feeding USAF command at the Korat Air Base in

Thailand. The hum was pretty high level and causing inter-modulation 

problems on the 60 channels of signal sideband suppressed carrier 

being applied to the microwave system.

We ended up with a couple of DCA DoD employees being flown in to help, 

to their credit they were prior service and darn good at what they did.  

After three days of testing all parts of the microwave system with a 

very long distance and long duration phone call to the manufacture in 

Calif, they still had not found the trouble.

I had stayed working with the DCA guys all of the time, during the 

testing I noted the hum seem to lessen in strength with someone standing 

directly behind the radio bay.

I went around to the back and took a close look, Yep! the mixer diodes 

for the baseband order-wire were glass and exposed.

Put a length of black tape over them and the hum went away.  Not the 

power supply problem everyone was fixated on, it was diode photo 

sensitivity.  I guess we could have just turned off the florescent 

lights too.

When I was 10 years old my father showed me how to use a Simpson

260 to check diodes and early transistors*. We were on the floor of the 

living room with sunlight streaming in.  I saw the forward resistance change

a lot when the glass diode was in sun light vs shade. It was this memory 

that prompted me to try the black tape.

All the MW systems in SEA later received a MWO to change out the 

order-wire board and I found that the assembly was a non-standard part 

of the microwave system just for military use.  Civilian deployment of 

that microwave system had no need for the order-wire.

Thanks for the quick trip, for me anyway, down memory lane and the 

memory of being an electronics tech hero for all of two minutes. The DCA 

guys made me buy the first round at the club.

73  from an old friend....

HB2HB QSO with KC1FSZ and his Al Fresco Scratch-built BITX

I had some good luck on the ham bands last weekend.  First, I was called by Bruce KC1FSZ -- this time he was on his Al Fresco scratch-built BITX-on-a-board.  FB.  The next day, I called CQ on what seemed like an empty 17 meter band.  I heard someone come back -- it sounded like DX.  I had to swing the Moxon a bit -- oddly, I thought, to the south-east.  FR5FC was calling me from Reunion Island.   TRGHS. 

Here's a follow-up message from Bruce: 

Hi Bill:

Great to catch up with you on 40m yesterday.  I was using the Peppermint II which is a scratch-build of the BITX-40 for the most part, although I did my own digital VFO/BFO and made a few other modifications in order to be able to use it on 80m.  It took about 8 months of noodling to get the thing to work, but it was a great learning experience. 

As discussed, I’m working on a 24V power supply (LM723 + 2N3055) and a push-pull IRF510 final so that I can get some more power.  

I got a few more Williams-Sonoma Peppermint Bark tins off of EBay so I’m ready to start boxing things up as soon as the linear is working. 

73s,

Bruce KC1FSZ

KD4PBJ's Acorn AM Broadcast Band Regen

From Chris, KD4PBJ: 

This is my AM band regen I built during December and early January. 

It uses a 955 acorn tube and is a really hot performer! I can pick up dozens of stations with only a 20 ft piece of wire thrown out my shop window and tied to a nearby tree limb 5 ft off the ground. This is from rural Tennessee where we have no local AM’s. 

It uses a velvet vernier I bought off eBay back around 1999 or 2000 and had saved for a special project like this. 

I’m running filaments off a 6V lantern battery and plates off a type 415 45V battery. 

A nice ham/machinist I met on the Time Nuts list who lives in San Francisco made my insulated shaft couplings. I got the Delrin rod cheap off eBay. He cut them to length, center drilled for 1/4 inch and drilled each end for 2 setscrews.

Understanding Switching Mixers (as in the Ceramic DC RX)

W3JDR's Comment on my post about the DC RX mixer got me thinking.   He was right -- my explanation of the mixer action wasn't quite complete, especially as far as switching mixers are concerned.  I remembered that I had written about this in the SolderSmoke book.  Below you can see the part of the book in which I discuss switching mixers.  Realize that the two diodes in F5LVG's mixer play the same role as the two gates in Leon's circuit.  It will be worth your while to sit down with Leon's circuit diagram, his frequency chart,  and a ruler and really go through this so you can SEE and really understand how the two gates (or switching diodes) generate sum and difference frequencies.  

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

I guess I still yearned for clarity and intuitive understanding...  Time and time again, as I dug into old textbooks and ARRL Handbooks and promising web sites served up by Google, I was disappointed. 

Then I found it.

It was in the Summer 1999 issue of SPRAT, the quarterly journal of the G-QRP Club.  Leon Williams, VK2DOB, of Australia had written an article entitled “CMOS Mixer Experiments.”  In it he wrote, “Generally, mixer theory is explained with the use of complicated maths, but with switching type mixers it can be very intuitive to study them with simple waveform diagrams.” 

Eureka!  Finally I had found someone else who was dissatisfied with trigonometry, someone else who yearned for the clarity of diagrams.  Leon’s article had waveform diagrams that showed, clearly, BOTH sum and difference output frequencies.

Switching mixers apply the same principles used in other kinds of mixers. As the name implies, they switch the mixing device on and off.  This is non-linearity in the extreme.

Not all mixers operate this way.  In non-switching mixers the device is not switched on and off, instead one of the signals varies the amount of gain or attenuation that the other signal will face. And (as we will see) it does this in a non-linear way.  But the basic principles are the same in both switching and non-switching mixers, and as Leon points out, the switching circuits provide an opportunity for an intuitive understanding of how mixers work. 

Let’s take a look at Leon’s circuit.  On the left we have a signal coming in from the antenna.  It goes through a transformer and is then applied to two gate devices.  Pins 5 and 13 of these gates determine whether the signals at pins 4 and 1 will be passed on to pins 3 and 2 respectively. Whenever there is a positive signal on gate 5 or on gate 13, signals on those gaps can pass through the device.  If there is no positive signal on these gates, no signals pass.  Don’t worry about pins 6-12.

RF A is the signal going to pin 4, RF B is the “flip side” of the same signal going to pin 1.  VFO A is a square wave Variable Frequency Oscillator signal at Pin 5. It is going from zero to some positive voltage.  VFO B is the flip side.  It too goes from zero to some positive voltage. 

Look at the schematic.  Imagine pins 5 and 13 descending to bridge the gaps whenever they are given a positive voltage.  That square wave signal from the VFO is going to chop up that signal coming in from the antenna.  It is the result of this chopping that gives us the sum and difference frequencies.  Take a ruler, place it vertically across the waveforms, and follow the progress of the VFO and RF signals as they mix in the gates.  You will see that whenever pin 5 is positive, the RF signal that is on pin 4 at that moment will be passed to the output.  The same process takes place on the lower gate.  The results show up on the bottom “AUDIO OUTPUT” curve. 

Now, count up the number of cycles in the RF, and the number of cycles in the VFO.  Take a look at the output. You will find that that long lazy curve traces the overall rise and fall of the output signal.  You will notice that its frequency equals RF frequency minus VFO frequency.  Count up the number of peaks in the choppy wave form contained within that lazy curve.  You will find that that equals RF frequency plus VFO frequency. 

Thanks Leon!  

F5LVG's Glue-Built Mixer Transformer

One thing I forgot to mention:  In Olivier F5LVG's DC receiver article back in SPRAT 100, he casually mentioned building a transformer for his mixer by taking two inductors of the appropriate values and GLUING THEM TOGETHER.   What a great idea!  I had to try it.  I did.  Picture above.  It worked in my Ceramic DC receiver, but the trifilar transformer from Farhan in India worked better.  Perhaps the coupling was tighter.  But hey, it worked.  Three cheers for Olivier.    

Building the Ceramic Discrete Direct Conversion Receiver #4 -- The Mixer

I think the most important stage of a direct conversion receiver is the mixer.   This is the stage that takes the RF energy coming in from the antenna and -- in one fell swoop -- turns it into audio.

It is important to understand how this happens.  I go into this in some detail in the SolderSmoke book.  To summarize: 

1) You have two signals going into a non-linear device.  The way in which the smaller signal passes through the device -- how much it is amplified or attenuated -- depends on the instantaneous value of the larger signal.  We are not just adding the two signals together.

2) The waveform that comes out will be a complicated repeating waveform.  We know from Fourier that any complicated repeating waveform can be broken down into sine wave components.

3) When you analyze the complicated repeating waveforms coming out of the mixer, you will find that the sine wave components include a frequency that is the sum of the two inputs and another that is the difference between the two.

So lets suppose we have a non-linear device.  We send in a signal from our oscillator at 7061 kHz. Coming in from the antenna we have a signal at 7060 kHz.   The non-linear device will produce outputs at 14121 kHz (sum)  and at 1 kHz (difference).  We are interested in the difference frequency.  We can HEAR that one.  We feed it into our audio amplifiers and we can copy the Morse Code coming in.  It will sound like a 1 kHz tone going on and off as the operator at the distant station presses his code key.  (We don't really have to worry about the 14121 kHz signal -- it is easily eliminated by filters and would never make it through our audio amplifiers.  And in any case we could not hear it.)

What can we use as a non-linear device?  In this receiver we will use diodes.  Diodes are  extremely non-linear devices. They can be used as on-off switches, with one of the signals determining if they are on (conducting) or off (not conducting).  When used like this they are "switching mixers." In essence, a larger,  controlling signal from the VFO will be turning the diodes on and off. Thus the signal coming in from the antenna will be chopped up by the switching action of the diode being turned on and off.  This is non-linear mixing at its most extreme.  It will definitely produce the sum and difference products we are looking for.

We could build the mixer with just one diode. You could apply the VFO signal to the diode to turn it on and off, and then feed the signal from the antenna into the same diode.   You would get the sum and the difference product out the other end.   You will see very simple direct conversion receivers intended for use in software defined radio schemes using just one diode. But this kind of circuit has a couple of serious shortcomingsq: it is susceptible to "AM breakthrough" and it is "lossy."

The circuit we are using addresses these problems by using two diodes.  To reduce loss, one conducts during half of the oscillator signal's cycle, the other during the other half.  Here LTSpice is ueful. You can model this mixer and see in the simulator how each of the diodes handles half of the oscillator RF cycle, with both contributing to the AF signal we want at the output (the difference frequency).   (The schematic above is from LTSpice but it is not ready for simulation.  For this you should replace the variable resistor with two fixed 500 ohm resistors, and add two oscillators -- one with the weak incoming RF signal and the other the strong local oscillator signal.)

The AM breakthrough problem is also addressed by the use of two diodes.  Here's the problem:  If you are on 40 meters, there will be strong shortwave AM broadcast signals coming in from your antenna.  Some will be so strong that they will get past your front-end filtering.  If you were using just one diode, that diode might demodulate the AM signal -- the AM carrier would mix with the AM sidebands and you would have an undesired audio signal heading for your AF amplifiers. Many of us have experienced this -- you are trying to listen to ham radio SSB signals, but you can hear China Radio International playing in the background. 

The two diodes take care of this easily. Look at the way an AM signal would reach the diodes. The carrier (and its sidebands) going through the top diode will be 180 degrees our of phase with the signal going into the lower diode. But the output of the diodes are joined together.  They will cancel out.  We say that for the RF signal coming through from the antenna, the circuit is "balanced."  That signal -- in this case the undesired AM signal -- will cancel out at the junction of the two diodes.

But to understand this circuit you must see what is NOT cancelled out.  The signal from the VFO is hitting each diode with the SAME polarity at the same time.  Look at the 1k variable resistor. So the signal from the VFO will NOT be cancelled out at the output.  Nor will the mixing products produced in the diodes.  That last sentence is the key to all of this.  The sum and difference products that result from the mixing of the signal from the antenna and the signal from the VFO SURVIVE.  They are not cancelled out.

We can easily select the one we want.  An RF bypass capacitor connected from the output of the mixer to ground will get rid of most of the VFO signal (7061 kHz) and most of the sum product (14121 kHz) while passing the audio to the AF amplifiers. 

When I built this detector I used a trifilar toroid out of a box of them that Farhan left with me back in May. I used two of the windings  secondary and one of the windings for the primary.  You might want to make a more simple transformer using an FT-43 type core.  I recommend W8DIZ as a source. 

I hope this explanation helps, and I hope I got it right.  Let me know if you see any errors in my explanation.  Tinker with the circuit when you build it.  You should be able to get it going.       

Complete Schematic

Mike Rainey and Heavy Metal AM Phone

Michael Rainey AA1TJ wrote:  

I can tell you exactly what's going on here. I'd just received a license upgrade from "Novice" to "General." My new license granted radiotelephone privileges and I was eager to try them out.

In the early 1970's no self-respecting amateur radio operator would dream of using amplitude modulation (AM) on wavelengths above 10m. It wasn't illegal, rather, it was frowned upon due to bandwidth issues, among other things.

But in my excitement - and in the time-honored spirit of, "don't ask permission, ask forgiveness" - I tuned my clunky, Heathkit DX-100 to the 40m radiotelephone band and began calling CQ on AM. Everyone that I contacted was very polite, but to the man they all mentioned how "odd" it was to hear an AM signal on 40m. I eventually took the hint, but not before I'd figured out that yakking on a microphone wasn't my thing after all. Morse telegraphy was my first and enduring love.

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

I think Michael's next phone transmitter was that voice-powered rig that he used in an attempt to cross the Atlantic with the only power source being his vocal cords. But even there, he was using his voice to send Morse.  

C'mon back to radiotelephone Mike.  There is more to life than dots and dashes!

SolderSmoke Podcast #202 Cover-Rig, SKN, Pete's Vector Boards, uBITX, K1BQT rig, MAIL

http://n6qw.blogspot.com/

SolderSmoke Podcast #202 is available: 

http://soldersmoke.com/soldersmoke202.mp3

13 Jan 2018

Opening music from Shel Silverstein and Dr. Hook and the Medicine Show.  

On the Cover of the Rolling Stone or  On the Cover of SPRAT magazine.

Travelogue and Weather Report

-- Bill's trip to the Dominican Republic.  SWL on the beach.  Return to the ice box.  

-- Dramatic events in California. 

-- Reading Chinese Sci Fi with lots of radio in it.  "The Three Body Problem" by Cixin Liu

Straight Key Night.  IN QRP MODE THANK YOU.  With nephew Jeffrey.  Annual event -- worked Jim W1PID  friend of Mike Rainey.  

Steve Murphy and Jeff Damm on QSO Today.  FB. 

Oh your rig is homebrew?  "It must be propagation." 

ER Reading about G3UUR

Hams avoiding 60 meters due to 100 watt limit.  SAD. 

Bill's Bench:    Continuing series on the Ceramic Discrete DC receiver.   Described  the oscillator and the AF amp.  Next we will do the Mixer.   The most interesting stage. Nephew John Henry and niece Helena visiting today. 

Pete's bench.  uBITX adventures.   

The K1BQT IC transceiver. 

The Vector Board building technique.  See http://n6qw.blogspot.com/

MAILBAG

Paul KA5WPL  Looking for project with his son.  Sawdust.  Thanks again  Steve Silverman.

Chris Waldrup OM PBJ thanks for the gift

Pete in contact with Sven Johnson

Chuck KE5HPY sent us picture of fashion model with boatanchors in background  Grayson recalled 73 magazine covers...

Pete WB9FLW        Bilateral  SBE-33 ad  "with inherent stability"  That's the best kind!

Bruce KK0S experimenting with AF amps for the DC receiver

John KE5ETX Attempting CBLA

Towers and Antennas in Church Steeples and on Mt. Washington (VIDEO)

Steve Murphy N8NM on QSO Today

It was really nice to sit back and listen to Eric's talk with Steve Murphy. 
Don't miss this one.  Listen here: 

https://www.qsotoday.com/podcasts/N8NM  

My notes: 

-- On  a Stingray bicycle patrol on garbage night, looking for radio parts.  FB Steve! 
-- Started with SWL.  A fine radio pedigree. 
-- Had an R-390A at age 16.  
-- Uses an LC meter to check on toroid windings. 
-- Steve:  Thanks for the kind words about inspiration. 
-- Manhattan And Ugly.    Mugly!
-- Planker!  Better on a Board!
-- Form Factor First, but then it never fits! Al Fresco! 
-- Packages arrive from China faster than they go across Israel. 
- - E-bay as a really good source for parts. 
-- Oh god, not an S-38E.  Stop torturing yourself Steve. 
-- N8NM: Radio Renaissance Man:  Runs a 2 meter repeater network.  Thinking of 900 MHz. 
-- Papa Legba -- I got it from a W9SCH via SPRAT.  He got it from Voodoo.
N8NM is chickenkiller.com   FB. 
-- Moderation?  Ha!  Good luck with that! 
-- An Electromagnetic Playground where Failure has No Consequences.  Well put. 

-Happy New Year Eric and Steve!  Thanks to  both of you. 

Straight Key Night at N2CQR

I did my part for the retro-Luddite-CW-Straight Key cause.   My HT-37 was kind of wheezing.  I may have to go in there to striaghten it out.  At times I had it cranked back to less than 5W (to maintain some semblence of QRP street cred). 

A highlight was the QSO with Jim W1PID.  Jim is a well-known QRPer and a friend of QRP Hero Mike Rainey.  Jim and I talked last year -- same date, same event, same rig. Jim has a really nice web site: http://www.w1pid.com/

My nephew Jeffrey joined me for the last two contacts.   He got a real kick out of it, both the CW and the SSB. 

31 December 2017

17S  P49MR   Martin – Back in the islands!  Like an annual QSO.

40CW  Pre SKN   W1PID on 40 with my HT-37. An annual event!  Jim running 75 watts

40CW SKN KF5RBR Dan in AR.

1 January 2018

40CW SKN W8HOG SKCC 87750 Perry in Ohio

40CW SKN N1CGP Dave in Maine using J37 key

40CW SKN WB4JJJ Al in Fairfax

40CW SKN K8SRB  Stan  in Ohio (with nephew Jeffrey with me)

17SSB WJ2N Andy in Florida (with Jeffrey in the QSO)

Jeff Damm WA7MLH on QSO Today

Happy New Year!    

There was so much wisdom and tribal knowledge in Eric Guth's interview with Jeff Damm WA7MLH. It was almost overwhelming. 

You should all listen to it.  Twice. At least twice: 

https://www.qsotoday.com/podcasts/WA7MLH
  
My notes:

-- I sympathize with Jeff's decision to go solid state and give up on high voltage after an encounter with an undischarged 600 volt capacitor.  
-- I really like the 1700 kHz IF with a 5 MHz VFO for an 80 and 40 meter receiver. 
-- Interesting that EE degree didn't help much in his efforts to understand ham gear.  Better to read Wes's books and Doug's. 
-- Tek Spectrum Analyzers were specially made to fit down a submarine hatch.  
-- Building and measuring just as important as studying the theory.  Inked-up text books. 
-- Learned ugly from Wes as a teenager. 
--Searched for old commercial gear to gut and use as homes for homebrew solid state gear. The enclosures,  panels and controls are very useful.   Great way to avoid metal work.  These rigs are no longer boatanchors!  Again, I sympathize.  I've sacrificed many Heath Lunchboxes and QF-1s.  
-- Jeff Builds the VFO first.  My preference too. But he understands Pete's AF-first approach. 
-- Finger on the input of the AF amp!  Buzz!  Yea! Step your way back to the front end.
-- ALWAYS one stage at a time.  
-- Osh Park Boards for standard circuit modules.  Like Legos. 
-- Cubic Feet of air variables.   Jeff has a lifetime stash.   
--Thinking about what was and should have been his section of EMRFD. Go for it Jeff. PLEASE! 
-- Hesistant about chips. Analog guy.  Would have been a huge time sink.  Analog guy.  
-- Buying parts on e-bay.  Fewer and fewer RF parts at hamfests. 
-- People reading QST Tech Articles for entertainment. Editor apprach: "Nobody will build it anyway." Handbooks giving priority to entertainment and less to information and education.