A Filter for The Mighty Midget's Mate

The story of my 80/40 meter three tube (all 6U8) superhet receiver is recounted here:  http://www.gadgeteer.us/erart.htm

I've been playing with this RX on and off for many years now.  Somewhere along the line I picked up a 455 kHz filter for it (I couldn't find the 455 kc crystals that Lew McCoy used).  Yesterday I finally got around to putting the filter into the receiver.

There is almost no info on this filter on the internet.  Here are the details"
Toyo Communications Equipment Company Ltd.  CM FILTER
Type: 455 -- 2.4 -- C     Date:  8- 69

On the bottom, there are four terminals.  They are marked "P" "B" "E" and "G".   Does anyone know what these letters signify?  

 I experimented and it seemed like putting a 455 kc signal into P and B, and taking the output from E was the way to go.   I've left G floating. It works, and the improved selectivity is very evident.   But I'm operating with no specs on the filter, so I may have it in there upside down and backwards. And of course, I am operating with my usual disregard for impedance matching issues.

Here's how I've placed it in the circuit: 

Ideas, suggestions and even admonitions would be appreciated.

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Rich Arland's Global Adventures in Wireless Electronics

Rich Arland's SKN Station

Hi Bill:

I am writing to tell you what a GREAT book "Solder Smoke" is. I really enjoyed it and I am amazed at how similar our paths are regarding electronics, ham radio and our journeys around the world. 

Although I am 16 years older than you I, too, got my start in radio at an early age: about 10, after I got nailed by my dad's console SW/AM radio prior to a Cub Scout meeting one evening. I just had to figure out how I received a shock from that big old receiver, which led me to a life long pursuit of the elusive electron, an interesting 50 year career in ham radio, a 20 year career in the USAF (Tech Controller, AFSC: 307), and ultimately teaching vocational electronics in the State Correctional Institution at Dallas, Pa. 

During my AF career I spent almost 17 years overseas: two tours in Japan (KA2AA--this was prior to recip licensing as we had the Far East Amateur Radio League in the SOFA), a three year tour at Lajes Field, Terceira Island, the Azores (CT2BH--this was prior to the Azores receiving independence from Portugal in 1976), a five and a half year tour at RAF Mildenhall, UK (G5CSU), and a brief stint in W.Germany (DA2NE) while working with 10th SF Group at Bad Tolz and SOTFE in Patch Barracks. Had 18 months in the 3rd Mobil Comm Gp in Tinker AFB, OK, and a twilight tour at Langley AFB, VA. 

The three years in the Azores was from 1970-73....it was extremely difficult to obtain a ham license at that time and there were only 9 of us licensed in the entire archipelago, as I recall. I was attached to the 1936 Comm SQ, and all we had for comms to support theUS Forces Azores mission were three HF ISB shots: one to Andrews AFB, MD, one to Rota, Spain and the other to RAF Croughton, UK. During that three year period I REALLY learned about HF comm and propagation. I was on duty the day, in 1973, when "the ionosphere turned off"! WE had a SID of such magnitude that it blotted out everything, and I DO MEAN EVERYTHING! We were lucky to hear AFRTS on the hill by the MARS station! During that tour we also performed comm support for the US Navy's Sea Lab project on Sao Maria, which was part of the SOSUS system. Ultra cool stuff!!! On more than one occasion during a mid shift, the Comm SQ chief of maintenance, CT2BC, would snag me from tech control, and we'd go intoLajes Airways (right down the hall) and grab a Scope Control Level, point the two HUGE LPAs toward the states and work a little DX on 20M !! Definitely NOT QRP! All this under the guise of "quality control"! It pays to have friends in low places!

During my UK tour, we initially lived off-base at Bury St. Edmunds. I had a Ten-Tec PM-2B and a tuner which I loaded into a chain link fence behind our house. I quickly worked Collin Turner, G3VTT, and soon became a card carrying member of the G-QRP-Club (#622) in 1979. To celebrate my 34th birthday, my wife Pat (KB3MCT) and Jo Dobbs, wife of George Dobbs, G3RJV, put together a surprise party for me after a Saturday at the RSGB convention near Birmingham. George Burt, GM3OXX along with Ronny, GM3JJG, furnished the haggis....and the single malt....needless to say we did have fun; all 25 of us packed into RJV's home! 

Hey, sorry for being long winded. Our backgrounds and travels are uniquely intertwined. Thanks for writing "Solder Smoke". I am procuring a hard copy (I read it on my Kindle) for my wife, as your insight into the "why things work the way they do" are perfect for her to help her with obtaining her Extra. I only wish I had it when I was teaching my electronics classes in prison. It would have made my job easier, that is for sure. 

Stay well, and I hope we can meet one of these days. In the mean time, I have to pull my Meade ETX out of storage and start watching the sky, and finish building about four model rockets for an upcoming launch weekend here in North Georgia. 

Rich Arland, K7SZ
Dacula, GA

Author: "The ARRL's Low Power Communications, the Art and Science of QRP (all four editions)

ReplyReply All

Move...book editors

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The Raspberry e-Bay Multi-Mode Beacon of M0XPD

From: Paul Darlington 
Subject: Multi-mode QRSS beacon on the Raspberry Pi
To: "Bill Meara" 
Date: Sunday, January 20, 2013, 8:32 AM

Hi Bill

Inspired by recent comment on your SolderSmoke blog, I got myself a DDS module from eBay.

Today I lashed it up to my new Raspberry Pi and now have CW and Hellschreiber pumping out on 40m.

I hope others will forgive my greedy use of the spectrum in transmitting "m0xpd :- Raspberry Pi" in Hellschreiber.

The story is here: http://m0xpd.blogspot.co.uk/2013/01/multi-mode-beacon-on-rpi.html

73 de Paul, m0xpd

http://m0xpd.blogspot.co.uk/2013/01/multi-mode-beacon-on-rpi.html

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Drake 2B Filter Madness!

Wow, WB4HFN has ALL the details here: 

http://www.wb4hfn.com/DRAKE/DrakeArticles/HenryFilter01.htm

--------------------------------------------
Grayson:  Good to hear from you on this snowy morning in DC.   Wow, that's a bit of 2B history I hadn't heard of. Seems like a bit of overkill to me.  Maybe it was aimed at people who were unconvinced of the effectiveness of the LC filters?   Somehow, to me, it just doesn't seem right.  If you want more selectivity from a 2B, the thing to do is Q multiply using that socket on the back.  73  Bill 

--- On Wed, 1/23/13, Grayson Evans wrote:

From: Grayson Evans 
Subject: New info on the Drake 2B
To: "Bill Meara" 
Date: Wednesday, January 23, 2013, 1:43 PM

HI Bill, 

I was looking through the Dec. 1963 issue of 73 and came across an ad for a "New Mechanical Filter Modification Kit" for the 2A and 2B.  IT says "like magic the Drake becomes a truly superlative SSB receiver"  Model DMF-2 $29..  Says sold exclusively by Henry Radio, but does not say if they made it or not.  

Has a photo showing a module that plugs in (maybe a tube socket?) right behind the VFO.  Module has a mechanical filter (Collins I presume), two IF transformers and a tube (probably the tube it substitutes for).   I have been looking through a bunch of old CQ's and 73's, early 60's, and I only saw this one ad.  Probably a rare accessory, but how knows.

Thought you might be interested.  

Take care,

Grayson

TA2ZGE - Ankara, Turkey

KJ7UM

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Swamping or Q-Killing

Sounds like some new TV series on the Discover Channel, doesn't it? Actually it refers to efforts to stabilize oscillators by reducing the Q of components that may be helping to turn the amplifier into an oscillator.   A 300 ohm resistor across the primary of the output transformer on my most recent version of the JBOT amplifier recently solved my instability problem.  As part of an effort to understand how and why I came across a CQ magazine article by Doug DeMaw.  The relevant passage appears above.  

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An SSB kit from Spain

The ILER-20 and ILER-40 SSB transceiver kits of Javier Solans,
EA3GCY, look very interesting.

For more info: http://www.qsl.net/ea3gcy/


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DSB Audio -- Why Worry?

In a recent post I mentioned my concern about shaping the audio frequency response of my DSB transmitters.   This concern was sparked by an article in the May 1993 issue of "Electric Radio" magazine.   John Staples, W6BM,  had an article (the first in a three part series) entitled "Good Audio." The article (like most of ER) was focused on AM rigs and, it seems to me, contains a lot of technical wisdom.  Here is the part I found most relevant: 

"Good hamband AM audio is not the same as hi-fi audio. A broadcast-quality transmitter fed with a broadcast quality mike would sound flabby and under modulated. The highs would be lost in the narrow bandwidth of the receiver. The low frequency component would dominate the modulation power, but would be lost to the low frequency roll-off in the receiver.  What's left of the mid-range would sound weak, and the signal would lack punch.  Proper response shaping results in audio that sounds powerful, natural and undistorted." 

This seems to apply to DSB (suppressed carrier) audio just as well. 

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How to shape audio in simple DSB gear?

How should we handle the need for frequency response shaping in simple DSB transmitters?  If we don't roll off the lows and the highs, we risk wasting a lot of energy on RF that will be outside the passband of the SSB rigs on the other end.  This is especially worrisome if we use those cheap electret mic's that seem to have response curves from DC to daylight (well, maybe not that high, but you know what I mean). 

This is not a real concern with SSB rigs, because that crystal filter keeps our signals on the straight and narrow (!) but with DSB rigs, what is the best SIMPLE way to keep the audio between 300 and 2500 hz?    Is there an alternative to the 741 op amp configured as an audio bandpass filter?  

73  Bill N2CQROur book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Il Fido -- A Simple Receiver from Italy

As part of a refresher course in Italian, I am reading a bunch of old radio magazines from Italy sent to me by Stephen.   There are some really wonderful projects in these magazines and I feel compelled to share them with the SolderSmoke community.  No full translations yet, but perhaps that would provide a good language learning opportunity.  For now, just schematics and drawings (aren't they beautiful?).   

This one is a simple crystal receiver with one stage of AF amplification.  It covers the AM broadcast band, the HF bands, and (apparently) VHF using a switch and three different coil/capacitor combinations.  You could make it a lot simpler by just building it for one band.  Looks to me like a nice rig for an Altoid tin. 

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C.F. Rockey, W9SCH, Homebrew Hero, SK

In podcast # 148 I recounted how I had turned to one of his articles, "Prolegomena for QRP Transmitters" for inspiration.   Just Monday Brian,  N1FIY,  e-mailed asking for info on how to find the article.  Today, Mikey,  WB8ICN,  let me know that on December 23, 2012,  QRP Hall of Famer C.F. Rockey,  W9SCH, had become a Silent Key.  

I've been a big fan of Rockey's writing and projects for a long time.  I was sad to hear that he had passed away, but I know that through his writing his influence will be felt in workshops and on the airwaves for a long time to come.  

Here's a sample of Rockey's writing:  http://n4trb.com/AmateurRadio/QRPp_Vol01_No03.pdf

Here's Rockey's obit:


Charles Franklin "Rock" Rockey, Jr.,
Whitewater, WI (1918 - 2012)
June 21, 1918 - December 23,2012
Charles Franklin Rockey, Jr., known as "Rock", age 94, of Whitewater, died on Sunday,
Dec. 23, 2012, at Fairhaven in Whitewater. Rock was born in Oak Park, IL, on June 21,
1918, the son of Dr. Charles F. and Ada (Nichols) Rockey. At an early age, he became
interested in ham radio, earning his amateur radio license at age 16. Operating as W9SCH
for more than seventy years, he made contact with ham radio operators all around the world. In 1996, he
was inducted into the QRP Hall of Fame. Rock graduated from Oak Park-River Forest High School in
1937. He enrolled in Elmhurst College, but interrupted his studies in 1942 by enlisting in the U. S.
Navy. He served as an aviation electronic technician in Port Lyautey, French Morocco, and in Naples,
Italy. After World War II, he returned to Elmhurst College, graduating in 1947.
Rock worked at Walhenius Institute instructing brew masters, then in the early 1950's, taught at
Milwaukee School of Engineering. From 1955-1979, he taught chemistry, physics and electronics at
New Trier High School in Wilmette, IL. He was also the faculty sponsor of the student radio station
WNTH.
On retirement, Rock and his wife (the late Frances) moved from Deerfield, IL, to Albany WI. Rock
became friends with the local farmers in Green County as a milk tester for the Wisconsin Dairy Herd
Improvement Association. In addition to contributing many articles to radio and scientific magazines,
Rock wrote two books: "Electrons, Atoms, and the World: Chemistry for the Young in Heart" and
"Secrets of Homebuilt Regenerative Receivers." He greatly enjoyed playing polkas on the accordion.
Rock is survived by his son, Joseph (Jane) of Highwood, IL; and two grandsons, Jonathan (Meghan) of
New York City, and William (Alexandria) of Esparto, CA.
A Memorial Service was held at Fairhaven in Whitewater. Memorial contributions are requested to
Fairhaven Senior Community, 435 Starin Road, Whitewater, WI 53190.



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Knack Story: Ryan's Rig

Bill,
      
... [I know] a young ham locally who suffers terribly from the
affliction of the "knack". Ryan, KJ6HBY, is 17, and an Extra class,
who earned his DXCC in a year. He is a great builder, starting out
building his first antenna a couple years ago by breaking apart an old
washing machine motor and unwinding it for the wire. Along the way he
has restored various rigs, i.e. HR10, S-38, IC707, etc and built a
BTX17 (17 meter version of the BTX20). Enclosed is a couple photos of
his latest creations. First, he hand carved a wood morse code key. It
actually feels and works well. Now he has build a single tube xmtr,
and after fussing with it, is pumping out 4 watts. Both of the kid's
folks are hams as well as his sister. I had an opportunity to visit
his shack the other day. It's a teenage ham's dream and a mother's
nightmare. Racks floor to ceiling with radios! If anybody has the
knack, Ryan does. Makes me think there is a future, we can sleep well
tonight.
73
Mike Herr
WA6ARA
DM-15dp
Home of The QRP Ranch

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But Why Did Swamping Resistors Cure JBOT Oscillations?

OK,  so as I mentioned in SolderSmoke 148 (apprently with screeching in the background -- sorry) I managed to tame a bad JBOT oscillation problem by placing 680 ohm resistors across the primaries of the broadband transfomers in the JBOT.  Now I'm wondering how/why this worked, and what we could do to make this kludge unnecessary.  

Am I correct in suspecting that at the problematic frequency of 250 kHz, the one or more of the tranformers are self resonant, and that the resistors just bring down the Q of the -- in effect -- tuned circuit?  This lowering of Q makes feedback and oscillation more difficult, right?  

Here is the background.   Read from the bottom up.   

There is an old saying in Spanish:  "No hay mal que por bien no venga."   More or less this is the same idea as: "Every dark cloud has a silver lining."  Well, the dark cloud was my techno-agony with the parasitic oscillations (see my plea for h elp from yesterday).  The silver lining was the e-mail from Edgardo, LU1AR, in Buenos Aires that helped me get rid of them.    Edgardo advised putting a resistor across the primaries of the JBOT amplifier stages.  This is an old "lower the Q" trick, the idea being that lowering the Q might help prevent the amp from self-oscillating.     I used 680 ohm resistors.   First I put one across the primary of Q1.  No joy. Then Q2.  No luck.  Then I put one right across the primary of that big output transformer.  That did it!  The parasitics disappeared.   And I still get a nice 4 watts of output.  Thanks Edgardo.  I hope to make a contact with this rig today. 

The real silver lining in this story comes, however, in the form of Edgardo's blog site.  Wow, what an inspiring example of Argentinian Knack.  Radios, telescopes, auto-giros.  This guy is also into homebrew DSB rigs.  Wonderful stuff.  Check it out.  (Google will translate it for you, if necessary, but even if you don't read Spanish, the pictures tell most of the story.) 

http://www.lu1ar.blogspot.com.ar/

I put this URL blog up on the SolderSmoke blog.  

Thanks to all who sent advice and encouragement.  Merry Christmas! 

--- On Sun, 12/23/12, lu1ar  wrote:

From: lu1ar
Subject: [BITX20] Re: JBOT taking off at 250 kHz
To: BITX20@yahoogroups.com
Date: Sunday, December 23, 2012, 9:56 PM

First. You must secure the RF decoupling of +B line. Use a bunch of small capacitors in paralell 1n and 100 nF with 22 uF electrolitic.
Second: Use 1Kohm resistor in paralell with primary of the transformers. Begin with the driver, then the 1st amplifier and then the output transformer.
Let us know results.
Regards.
Edgardo Maffia LU1AR
Buenos Aires - Argentina

--- In BITX20@yahoogroups.com, "iam74@..." wrote:
>
> 
> 
> --- In BITX20@yahoogroups.com, Bill Meara wrote:
> >
> > I'm building my FOURTH JBOT and this one is giving me more trouble than all the others combined.   I seek the help of the group. 
> > Here are the details of my tale of woe:
> > 20 meter rig.  Double Sideband.   The JBOT is fed by a simple two-diode, trifilar toroid singly balanced modulator.  NO DIPLEXER TO SPEAK OF.  At the output of the balanced modulator there is a 1000 uH choke to ground and a .001 uF cap to the input of the JBOT.  AF amp is an LM-386.  VXO is a very simple MPF-102 one stage ceramic resonator VXO with no buffer stage.  7 element low pass filter (three coils, four caps). 
> > All the transformers are wound on FT-37-43 cores.  T3 is four such cores stacked 2X2.
> >  
> > The arrangement works beautifully into a 50 ohm dummy load.  But as soon as I connect it to an antenna (a dipole out in the yard, fed with 50 ohm coax) the output signal gets ugly.  
> > Looking at it on the scope, instead of the nice figure eight pattern (similar to the two tone test pattern of SSB) I get ugly fuzzy outcroppings from the peaks.  Looking at the signal more closely I can see that in addition to the 14.2 Mhz signal, there is another LF oscillation at around 250 kHz. 
> > I've been struggling with this.  I can't get rid of the LF oscillations. The leads are all short and the inputs are far from the outputs.   I've beefed up shielding, and decoupling.  I've sacrificed a chicken to Papa Legba. Nothing seems to help.  
> > I THINK the feedback/oscillation is taking place in the JBOT itself -- not through the
> > audio amp or the balanced modulator or the VXO.
> > I watch the RF and the AF inputs to the balanced modulator to see if there is any difference between the stable situation (with the 50 ohm dummy load) and the unstable situation (with the antenna),  I don't see any differences. 
> > I even put an antenna tuner between the final and the antenna anb made sure that the antenna looks like 50 ohms non reactive.  This seems to help a bit, but the ugly instability is still there. 
> > Help me! 
> > 73  Bill N2CQR    
> >
> 

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Move over Altoids Tins! Legos for Raspberry Pi Case

Too bad the Raspberry Pi board is a bit too big for our beloved Altoids tins.  It would have been a very fitting match:  British board in a British box.   A twelve year-old has solved the problem with Legos:  http://blog.makezine.com/2012/06/11/lego-raspberry-pi-enclosure/
Will this lead to raids on the toy boxes of the grandchildren of SolderSmoke fans? 
Billy's RasPi is running nicely (but no Legos for him).   

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Signal Generator Ideas

Hi, Bill

Howzabout a generator that goes from 1 Hz to 40 MHz with 1 Hz resolution, adjustable cursor so you can step any of the 8 digits, presettable offsets for if frequency, repeater offset, or r.i.t., directly synthesized output so almost no phase noise and 12 bit waveform accuracy? How about a price tag of less than $20 for all the major parts? Start by Googling dd_synth.asm for control software, and rather than buying the PCB recommended in the notes at the head of the program, search for AD9850 on Ebay for the synthesizer board and LCD 16x2 for the display. A 16f628a PIC is a couple bucks. Both the display pinout and the synthesizer pinout match standard perfboard. For a little more than $10 more get the AD9851 board and the upper frequency limit is 60 MHz.

A better way to transistorize the old tube-type generator is to use a dual-gate RF mosfet for the oscillator. You can trim the gain for waveform purity by adjusting the bias on gate 2. Once you find the optimum bias on each band, diode-switch the bias level with the bandswitch. Since gate 2 has an extremely high impedance you can use resistors in excess of a megohm, so it won't affect the Q of the tank coil.

Jim Daldry
Raleigh NC

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Opening Scene of Contact (CQ at the end)

Mike Herr's video on his use of an Arduino to call CQ SKN made it onto Hack-A-Day 
yesterday and provoked some discussion there of the meaning of CQ.  One fellow posted 
this opening scene from the movie Contact.   I thought you guys would like it. 

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Arduino Does Straight Key Night

Bill,
     Hope a good Christmas and excellent New Year. Here at WA6ARA we had a blast for Straight Key night . In the past I have used new keys, old keys and multiple keys. This year we celebrated SKN with a little twist. At Pacificon I purchased a hugh CW key, all made out of wood, about 3 times the normal size J-38. This isn't a QLF key but a piece of beautiful wood working, and fully functional. This was my main key for SKN.
But SKN can require the sending of CQ SKN for a considerable amount of time. Normally a programed keyer would do the job fine. But this is not in the true spirit of SKN, the use of the straight key. So, using a trusty Arduino board and a few lines of programming,  I solved the practical and ethical problem. The Arduino drives a model airplane servo. The servo is positioned such that it's arm presses down on a miniature J-38 key, thus sending the "CQ SKN". Also the miniature J-38, about half size, sort of balances out the larger size of the
hand key, and keeps the universe in check. I've enclosed a short youtube for your viewing enjoyment

http://youtu.be/Rn7Ky9Ib7ug

73
-- 
Mike Herr
WA6ARA
DM-15dp
Home of The QRP Ranch

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Like a Hamfest, but kind of EVIL

For a look at how the hackers do their version of the Dayton ham-vention, check out this video on DEFCON:   http://vimeo.com/56234900

Looks sort of like "Four Days in Hell" to me!  Finally, a group that makes hams seem normal and well-balanced! 

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A Nice Hallicrafters S38-E Knack Story

Bill - 

It was Christmas of 1958 (5th Grade)that my parents bought me the Hallicrafters S38-E that I still have.  I was recovering from multiple surgeries the previous summer to correct for the effects of Polio when I was 3.  I came down with Polio in the last year before the vaccine was released to the public.  

A bit of bio - because of my physical limitations as a child, I spent a lot of time indoors reading and listening to the radio.  Broadcast AM here at that time was still playing dramas like "The Lone Ranger" and "Big John and Little Sparky".  I really enjoyed them.  Then, on that fateful day I asked my mother why, since our radio plugged into the wall electric outlet and we could hear people talking, weren't other people able to hear us talking on their radio if we spoke into the loudspeaker.  She said, 'I don't know, but the library ( 2 blocks away) will have books about radio that you can read."  The Knack bit early and it bit hard.  

By the time I was in 5th grade I had discovered short wave radio.  I dearly wanted a short wave radio and I wanted a Hallicrafters.  Somewhere I had found a catalog and wow! nothing else would do.  What I didn't realize until I was in my teens was just how hard times were for my folks.  Most families then did not have medical and hospitalization insurance.  My dad was paying off the hospital and the doctors every month almost until I graduated from high school.

But, anyway, I did get the S38-E for Christmas.  At $69.95, it was the least expensive Hallicrafters available.  In reality, it is just an All-American - 5 with extended tuning range.  Tuning was as broad as a barn door, and above 15 MHz it is as deaf as a post.  But it was mine and I loved it.  The short wave bands were still hot in those days as we were just peaking through one of the most celebrated Solar Maxima of the last century.  Many the hours I listened to HCJB - Quito, and Radio Moscow, and Voice of America....   I also found people talking to each other - Wow!  Ham Radio.  And just look at me now.... And those strange beeping sounds - that was actually people talking? And what was that strange Donald-Duck sounding talk all about?

Yes - I still have that same S38-E.  It went to college with me, and has been with me for over half a Century, now.  Yes, it still works. (Needs a replacement IF transformer),  Yes, it will shock the bejeebers out of you if you plug it in wrong.   {I use two filament transformers back-to-back to prevent that.)  Yes, the Knack still has me, but that's another chapter.

72's 
Bruce  KK0S

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

High Pitched Audio QRM in SS #148

Two listeners blessed with good high frequency hearing alerted me to the fact that the latest podcast had some annoying high pitched noise in the background.   Peter, VK2TPM was the first to report it -- he sent along the above spectral analysis of a gap between words.  Steve,  W1KF,  also heard it, and provided a clue that I think solved the mystery.  

Steve noted that the noise was not present during the sponsor ads that were included in this episode. 
That let me figure it out.   On Saturday when I was recording this,  I got through about half the show when the power went out (that happens a lot here).  The battery in the laptop I was using to record the podcast saved the day and no data was lost.  The power came back on within a few minutes, but the outage had turned off the main PC in the shack.  That PC (AND ITS FAN) remained off when I was recording the ads.   I did the same kind of noise removal processing that I always do, but this time the noise sample that I used was taken from the mic with the main PC (AND ITS FAN) turned off.  My guess is that the whine from the fan (which I can't hear due to tinnitus) didn't make it into the noise sample, and thus didn't get removed from the podcast audio.    I went back and did a couple of rounds of noise removal and low pass filtering.  I think (I HOPE) I got rid of the offending noise. 
I have uploaded a new and hopefully improved version of the podcasts.  Audio reports will be appreciated.   

One of my New Years resolutions is to improve the technical and substantive quality of the podcast. 

Thanks Peter, Thanks Steve. 

Happy New Year to all! 
  
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SolderSmoke Podcast #148

SolderSmoke Podcast #148 is available:
http://soldersmoke.com/soldersmoke148.mp3
December 30, 2012

SPONSORED BY usedradiomall.com

-- Hurricane Follow-up
-- Subliminal Mind Control to Encourage Homebrewing (beep-beep)
-- The Shortcomings of the All American Five Receiver
-- Solid-Stating a Heath SG-6 (with Farhan's circuit)
-- VK3YE's Beach DSB Rig
-- Tek 'scope connection to frequency counter
-- Mod to W7ZOI/W7PUA power meter
-- JBOTing my 20 meter DSB Rig -- A Tale of Woe
-- LU1AR "The Most Interesting Ham in the World"
-- Billy's Raspberry Pi
-- Latest QST, SPRAT, Hot Iron
-- Videos: Landfillharmonica,  Knack in Sierra Leone
-- Santa delivered a Soldering Station
-- MAILBAG

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

He Should Have Used a Low Pass Filter!

http://www.sun-sentinel.com/news/broward/hollywood/fl-pirate-radio-hollywood-20121229,0,5142922.story

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

A Christmas Present from Argentina

There is an old saying in Spanish:  "No hay mal que por bien no venga."   More or less this is the same idea as: "Every dark cloud has a silver lining."  Well, the dark cloud was my techno-agony with the parasitic oscillations (see below).  The silver lining was the e-mail from Edgardo, LU1AR, in Buenos Aires that helped me get rid of them.    Edgardo advised putting a resistor across the primaries of the JBOT amplifier stages.  This is an old "lower the Q" trick, the idea being that lowering the Q might help prevent the amp from self-oscillating.     I used 680 ohm resistors.   First I put one across the primary of Q1.  No joy. Then Q2.  No luck.  Then I put one right across the primary of that big output transformer.  That did it!  The parasitics disappeared.   And I still get a nice 4 watts of output.  Thanks Edgardo.  I hope to make a contact with this rig today. 

The real silver lining in this story comes, however, in the form of Edgardo's blog site.  Wow, what an inspiring example of Argentinian Knack.  Radios, telescopes, auto-giros.  This guy is also into homebrew DSB rigs.  Wonderful stuff.  Check it out.  (Google will translate it for you, if necessary, but even if you don't read Spanish, the pictures tell most of the story.) 
http://www.lu1ar.blogspot.com.ar/
Thanks to all who sent advice and encouragement.  Merry Christmas! 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Woe is me! Why Podcast is Late: Parasitic Oscillations!

I'm building my FOURTH JBOT and this one is giving me more trouble than all the others combined.  
Here are the details of my tale of woe:
20 meter rig.  Double Sideband.   The JBOT is fed by a simple two-diode, trifilar toroid singly balanced modulator.  NO DIPLEXER TO SPEAK OF.  At the output of the balanced modulator there is a 1000 uH choke to ground and a .001 uF cap to the input of the JBOT.  AF amp is an LM-386.  VXO is a very simple MPF-102 one stage ceramic resonator VXO with no buffer stage.  7 element low pass filter (three coils, four caps). 
All the transformers are wound on FT-37-43 cores.  T3 is four such cores stacked 2X2.
 
The arrangement works beautifully into a 50 ohm dummy load.  But as soon as I connect it to an antenna (a dipole out in the yard, fed with 50 ohm coax) the output signal gets ugly.  
Looking at it on the scope, instead of the nice figure eight pattern (similar to the two tone test pattern of SSB) I get ugly fuzzy outcroppings from the peaks.  Looking at the signal more closely I can see that in addition to the 14.2 Mhz signal, there is another LF oscillation at around 250 kHz. 
I've been struggling with this.  I can't get rid of the LF oscillations. The leads are all short and the inputs are far from the outputs.   I've beefed up shielding, and decoupling.  I've sacrificed a chicken to Papa Legba. Nothing seems to help.  
I THINK the feedback/oscillation is taking place in the JBOT itself -- not through the
audio amp or the balanced modulator or the VXO.
I watch the RF and the AF inputs to the balanced modulator to see if there is any difference between the stable situation (with the 50 ohm dummy load) and the unstable situation (with the antenna),  I don't see any differences. 
I even put an antenna tuner between the final and the antenna anb made sure that the antenna looks like 50 ohms non reactive.  This seems to help a bit, but the ugly instability is still there. 
Help me! 
\

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

LadyAda Named Entrepreneur of 2012

Watch this video and you will see that Limor Fried has The Knack!
She and her company have brought homebrew electronics back to lower Manhattan.
Some kind listener sent me a gift certificate for Ada Fruit.  We will put it to good use, probably
with Raspberry Pi and Arduino gear.
Three cheers for Lady Ada!

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Roadkill Violins! LandfillHarmonic

Landfill Harmonic film teaser from Landfill Harmonic on Vimeo.

Wow, this is a really inspiring video about being inventive, overcoming obstacles, using what you find and putting junk to good use.  I thought you guys would like this (ESPECIALLY ROBERTO!).

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

FITSAT-1 Flashing Morse With LEDs from Orbit

Very cool:  Japanese students sent up a small satellite.  One of its capabilities is to flash Morse code messages in the visible light range using LEDs.   Prepare to peg your geek meter: 
http://www.fit.ac.jp/~tanaka/fitsat.shtml 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

PE1JXI's BITX-20 Handheld

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20