Dean's Tiny Tia -- Hardcore Homebrewing

 

Hi guys,

I've been on kind of a building hiatus due to various issues, but after seeing the work being done with the termination insensitive amplifiers I had to start noodling again.....as Pete would say.  Well I have decided to build a TIA (ZIA according to Pete) SSB transceiver.  I've decided to homebrew everything including the DBM, crystal filter, and even the Si5351 module.  As I wait for more parts to come in, I wanted to show the 2 TIA amps and crystal filter assembly I've built.  I've included a screenshot of the pass band response through the amps and the crystal filter.  It looks the same in both directions and everything fits into an area of 2 x 2.5 inches.  With the space left on the board, I hope to be able to put my SBL-1 clones on as well.  I follow up as I get more completed.

73

Dean AC9JQ 

 

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's LBS II Transceiver

Look at that.  That is the work of a master homebrewer.  More info and more great pictures here:

http://www.n6qw.com/LBS2.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

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