Been There, Done That: "...he begged his oscillator to osc and his amplifiers to amp."

This ad is from the December 1931 issue of QST.   This copy has a LOT of mileage on it.   In 1993 or 1994, David Cowhig (now WA1LBP) was living in Okinawa Japan and was operating as 7J6CBQ.   I was living in the Dominican Republic and operating as N2CQR/HI8.   We were both contributing to a 73 magazine column (as "Hambassadors"!) and we were both in the Foreign Service.   I wrote to David -- he wrote back, sending me some old QSTs, including the one from which the above ad is taken.

This ad shows that many of the homebrew/troubleshooting woes that we face today are very old.  And that having access to good technical books is very important when you are trying to overcome these difficulties.  

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

Peter Parker Reviews a DSB Kit and Presents Cool Mods (3 Videos). Also: Why DC Receivers Don't Work with DSB sigs. (It doesn't seem fair!)

I found Peter's recording of the DSB signal being received by a DC receiver to be very interesting.  We've long been warned about the very ironic incompatibility of DSB rigs and DC receivers. 

In "W1FB's Design Notebook," Doug DeMaw wrote (p 171):  It is important to be aware that two DSSC (DSB) transmitters and two DC receivers in a single communication channel are unsatisfactory.  Either one is suitable, however, when used with a station that is equipped for SSB transmissions or reception. The lack of compatibility between two DSSC (DSB) transmitters and two DC receivers results from the transmitter producing both USB and LSB energy while the DC receiver responds to or copies both sidebands at the same time."     Bummer.

In essence, we've been warned that the simple DSB/DC rigs we've put on the air cannot communicate satisfactorily with similar rigs.  We are, it seems, doomed to only speak with SSB/Superhet rigs.

The later portion of Peter's second video allows us to hear just what happens when we try to listen to a DSB signal with a DC receiver:  It sounds, well, unsatisfactory.   I was trying to figure out why.  Here are some ideas:

Simplify things by assuming we are transmitting only a single audio tone of 1000 Hz through our DSB transmitter.  The rig's VFO  is at 7100 kHz.  The 1 kHz tone results in signals at 7101 and 7099 kHz.  Along comes somebody with a Direct Conversion receiver. If he were able to put (and keep) his receiver oscillator on EXACTLY 7100 kHz,  he would end up (by taking the difference products from the product detector) with  a 1 kHz tone resulting from the 7099 kHz signal AND a 1 kHz tone from the 7100 kHz signal.  But there would be phase differences between these two signals, so you would end up with a less than pure 1kHz tone. (Did I get that right?)  And if -- as is likely -- your local oscillator is a bit off frequency you'd get a real mess.  If for example the local oscillator was at 7100.1 kHz, you'd have tones at   900 Hz (7100.1 - 7101) and 1.1 kHz (7100.1 - 7099).      Yuck.  

You might think you could just use the local oscillator in your DC receiver to replace the carrier in the DC receiver, turning it into an AM signal, then use an envelope detector as you would with any AM signal.  But not so fast!  For this to work your local oscillator would have to be not only at the same frequency as the original carrier, but also in the same phase.  That is hard to do. (Hard, but possible -- that is what they do with synchronous detectors using phase locked loops.)

I think you can actually hear many of the DC-DSB problems as Peter tries to tune in the DSB signal of VK7HKN using the DC receiver in the MDT transceiver.  It is indeed unsatisfactory.    But don't worry.  It is highly unlikely that when using a DSB rig you will encounter another DSB rig.  I speak from experience on this.  Pity.



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

Tonight is the "Night of Nights"

 

 

From "The SWLing Post" we learn that tonight may be the last opportunity for us to listen to CW from U.S. Coast Guard stations:

 

http://swling.com/blog/2015/07/night-of-nights-xvi-july-12-2015/  

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

Interview in China with Arduino's Massimo Banzi: "Be nice!"

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

KC2THY's Mighty Mite - A Thing of Beauty

Bill,

I have been a listener of the Soldersmoke Podcasts for several years now and I have worked my way through most of the back episodes of the podcast. It is terrific production and has taught me so much about radio electronics. I have also read all of your books. Thanks for what you do for this hobby.

Attached is a photo of my recently completed Michigan Mighty Mite.  The FFT function in my scope confirms a good clean signal and it sounds great when I listen to it on another radio. I am sure that the photo depicts one of the worst looking MMMs to date. I built it on a solderless breadboard as I have never built anything using Manhattan or ugly construction techniques. It was a great introduction to very basic homebrew electronics.

Thanks again,

John Stockman, KC2THY

Morristown, NJ

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 Dreams (and Nightmares)

 

 

 

Bill,

I've just listened to Solder Smoke episodes 168-170 and I'm following your advice.  My Michigan Mighty Mite sits on my desk only lacking the variable capacitor.  I was amazed that I had everything needed in my junk box!  Including a 3.575611 crystal.  

Last night I dreamt that the incomplete breadboarded Mighty Mite was beckoning me.  I walked over to the desk and I had the palpable sense that the Mighty Mite itself wanted to oscillate, as if by arranging the components in this way I created something alive.  I touched the tank and it began oscillating by itself without the variable cap.  The universe seemed complete in that sweet moment.  

When I awoke I attempted to replicate the event unsuccessfully.  haha.  I definitely need a variable capacitor....  

Regards,

Bryan 

KV4ZS

 

 

Bryan:   You might be able to make your dream come true with a fixed value cap.  Do you have something of about 150 picofards?    Try that.   It might work.   Or do you have an old transistor radio that could sacrifice its tuning cap?   
 

I have had similar homebrew dreams.   Well, nightmares mostly.   I dreamed that in a fit of frustration I took ALL the parts off the BITX 17 board.   That was a scary one.   I'll cc Steve Silverman to see if he could help with the variable cap.  

73  Bill

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

The Wizard of Warrenton: Jerry KI4IO

 

That's Jerry KI4IO of Warrenton Virginia sitting in front of truly impressive collection of homebrew gear.  The cream-colored box above the Vibroplex is Jerry's new 7 MHz phasing transceiver.   He has a wonderful write-up of this rig in the qrp-tech group files section:

https://groups.yahoo.com/neo/groups/qrp-tech/files/KI4IO/

You may have to join the yahoo group to access it, but believe me, it is worth it.  Jerry took a very eclectic approach to circuit selection and came up with a very cool rig.  Lots of soul in that new machine!  Here it is in breadboard form:

 

 

Jerry worked in U.S. Embassies as a communications officer and is obviously a member of the International Brotherhood of Electronic Wizards.  From his QRZ page:

 

While in India I was licensed at VU2LHO and worked a lot of US hams with a 135' flat-top and open-wire feed. I had the antenna strung between two bamboo towers atop the embassy housing 2ND-story roof-top. I also put up a 3/8 wave vertical on the roof for 10 meters. That little antenna had 110 radials stapled into the roof scree and worked very well! The rig was a HW-101. I was in Kathmandu, Nepal from early 1980 to late 1982. I could not obtain a license there, but became good friends with Father Moran, 9N1MM, and would often spend time up at his place putting his Drake station on CW. Pretty cool being real DX!

 

Warrenton, Virginia is not far from my QTH (it is the birthplace of Cappuccio the wonder-dog). 

 

FB Jerry. 

 

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

Pete Shrinks the Transceiver (Video)

Pete writes:  This video shows the LBS XCVR shrunk down to a mainboard that is 2.5 Inches by 4.5 inches. The board contains the 20 Meter Band Pass Filter, the RxTx Mixer, a TUF-3, two bilateral amplifier stages a 5.185 MHz Homebrew Filter. a TUF-3 PD/BM. The Audio amp stage and the microphone amp. Not built as yet is the bi-directional stage that on receive is the RF amp and on transmit the Tx pre-driver stage. Extensive use of SMD components makes the size reduction possible. The transmit final stages will be on a 2nd board that is stacked on top of the mainboard. An Arduino Pro-Mini does all of the control for the Si5351 VFO/BFO. The final size will be 4X6X2. Oh it also has a color display! http://www.n6qw.com/.

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

Bob Crane's Interviews at Four Days in May 2015

Once again our correspondent in Dayton, Bob Crane W8SX, has done an excellent job in interviewing the presenters at the Four Days in May event.  Through Bob's interviews we hear from:

-- George Dobbs, G3RJV. George puts the "L" back in solder and is asked to comment on his recent (richly deserved) awards. 

-- G4GXL talks of his new duties as President of QRP ARCI.

-- K8IKE  Talked about looking at the amateur radio station as a system.

-- KC3BRA talks about coming to ham radio from the Hacker/Maker world.

-- KW5GP  talks about his new book on Arduinos in ham radio.

-- W1RFI talks about the work of the ARRL lab.

-- M0XPD talks about new trends in  ham radio involving microcontrollers.  Paul also talks about Pete Juliano N6QW.  Pete had asked Paul to accept on his behalf the QRP Hall of Fame induction plaque. Well done Paul.

You can listen to or download the podcast here:

http://soldersmoke.com/SolderSmokeSpecial FDIM 2015.mp3

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 Really Interesing Interview with Elecraft's Wayne Burdick, N6KR

http://www.qsotoday.com/podcasts/n6kr
 
Eric 4Z1UG does a podcast called QSO Today.   He interviews interesting hams.   A few days ago I listened to his talk with Wayne Burdick, N6KR, as I worked on my Tuna Tin 2/Herring Aid 5 rig.   It was the  perfect accompaniment, but the interview was so good that I intend to listen to it again, this time with no distractions from melting solder.  Thanks Eric.  Thanks Wayne.   Here it is.  Just click on the "Listen to podcast"" button:

http://www.qsotoday.com/podcasts/n6kr
  
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

Two Party Balloons, an Arduino and an Si5351 FLY! ALOFT! UP IN THE AIR!

http://www.qrp-labs.com/ultimate3/balloon.html

Farhan alerted me to this.  This is clearly the coolest use so far of the Dynamic Duo (Arduino+Si5351).

It took me a moment to get my head around this.  It is so fantastic.  Let me break it down for you:

You take two party balloons.  You build a little payload consisting of an Arduino Nano, an Si5351 board, a GPS module and a battery.  You load the Nano with firmware that will take the GPS info and transmit it via WSPR and JT9.   Then you release the whole thing and sit back to receive the telemetry packets that tell you where the thing is.  Very cool.  Very cool indeed.  

THE Si5351 SERVES AS THE WHOLE TRANSMITTER.  It connects to the antenna.  (Steve Smith will, I'm sure,  insists on a low pass filter, even here!)

Here is a similar project: 

http://picospace.net/

And be sure to stop by the QRP Labs online store.  Lots of good stuff there:

https://shop.qrp-labs.com/

I've been interested in balloons for a long time.  A few years ago Billy, Maria and I released a party balloon over Northern Virginia with a note requesting that the finder send us an e-mail (It landed about 10 miles away, across the Potomac river, in Washington D.C.).   Here is a picture of a paper-mache hot-air  balloon that we built and flew near Lavallette, New Jersey (Ocean Beach Unit III) sometime around 1969.  Many of the kids in the picture are my cousins:

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

Farhan's ATU (and his new blog!)

Farhan has built a very cool antenna tuner.   More important, it is the subject of the first of what we hope will be many postings on his new VU2ESE blog.   I really like the re-purposed Sony meter, and the homebrew feedline for the multi-band (80-6 meters) doublet.  This is clearly a suitable antenna and tuner for the multiband Minima.  I have been inspired!  I hope to brew up some feedline soon!  No more store-bought transmission line for me! 

VU2ESE Blog:  http://hfsignals.blogspot.com/p/about.html

VU2ESE Tuner Article:  http://hfsignals.blogspot.com/2015/06/a-balanced-tuner.html


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