OOPS! Why the AD9850 DDS Boards are So Inexpensive

N3ZI has a very plausible explanation for the low price (about 9 bucks!):

My guess is that this is a liquidation due to a design build error, since they are being sold for a price of about 1/2 the price of the DDS chip alone. The modules are assembled and tested. The design error I noticed is that the wrong output filter is used. These boards use the 9850 running at 125MHz. A 125MHz DDS should have a 50MHz LPF, but it seems that these modules have the 75MHz LPF the chip maker recommends for the AD9851 running at 180MHz. My guess is, someone just copied the wrong filter from the wrong data sheet, and it wasn't caught until they went into production.
But for amateur radio applications they work fine up to about 40MHz. You can push them to 50MHz by adding a correcting filter, which is included in my controller PCB, but the output level is low in the 40-50MHz range.

N3ZI continues to offer some really interesting microcontroller products.  He has a controller board that allows you to simultaneously control TWO AD9850 boards.  This might be exactly what we need when we have a separate receiver and transmitter with different intermediate frequencies: Set up one board with the VFO freq for the receiver and the other for the transmitter with the resulting operating freq displayed on the LCD.  Viola! No more "Spot" or "net" and zero-beat by ear! (But I may be one of the last people on the planet still doing this!)   

N3ZI's site:  http://www.pongrance.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

R-390A and Homebrew TX put in Transceive Mode (VIDEO)

N8ZRY has a very nice video on his recent adventures with the legendary R-390A receiver (want one!) and his homebrew 20 meter SSB transmitter.  He manages to essentially put the receiver and transmitter into "transceiver" mode.  Very nice.  I wonder if he had previously used the old standard "spot" or "net" "zero beat by ear" method?  This video has me thinking about ways to bring my many separate receivers and transmitters closer together. The problem is that they all use different IF frequencies (the crystal filters are at different frequencies).  But using my Arduino-based DDS VFO, I guess it wouldn't be too difficult to program the thing to generate one VFO freq for transmit, and a different VFO freq on receive, in effect putting the transmitter and receiver on the same frequency. 

Both the R-390A and the homebrew transmitter look great.   Thanks Greg!


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

Dutch Knack During WWII

 

 

There is a very nice article on the MAKE blog this morning: 
http://blog.makezine.com/2013/06/06/an-early-maker-story-from-holland/
 
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

Quote of the Day: On Tinkering

Finally, some justification for my "build first, design later" method:

"Contraptions, machines, wildly mismatched objects working in harmony -- this is the stuff of tinkering.  Tinkering is, at its most basic, a process that marries play and inquiry."

from www.exploratorium.edu/tinkering   Quoted in Massimo Banzi's book "Getting Started with Arduino."

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

Alan Yates, VK2ZAY, is back in the knack!

I was getting kind of worried.  I hadn't seen any new articles on Alan's excellent web site.  But on my last visit I learned that he has moved to Seattle and is going to Maker Faires:  http://www.vk2zay.net/article/268

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

Save 20% on Knack Books

Codeword: GLOW.   Very appropriate for Grayson's Thermatron book: 



http://www.lulu.com/shop/grayson-evans/hollow-state-design/paperback/product-20987562.html


And also for mine (tubes, QRP fireflies and all that):



http://www.lulu.com/spotlight/soldersmoke

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

1-29 MHz In One Small Box

 

This weekend I put the Arduino/AD9850 Direct Digital Synthesis device into a box this weekend.  It is sort of evolving into a general purpose HF signal generator and/or VFO.  It is really kind of neat that this little collection of boards can generate RF across that range, with accurate digital readout.  Thanks again to Richard Visokey, AD7C, for the circuit and the code.  As you can see, my cabinet making skills will never land me a job on the Discovery Channel,  but I'm kind of pleased with the box.  I picked up the wood panels from a hobby/craft shop. 



 

 

I left a lot of space in the box.  I envision an amplifier taking the output from its current .4 milliwatts up to around 10 milliwatts, followed by step attenuators (pads).

 

Here is the other end.  Of course, I could have just taken the ATMega chip out and avoided putting the whole Arduino board inside the box, but I'll leave that exciting digital adventure for a future project.


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

Simple Homebrew SDR

I know that "simple" and "homebrew" aren't the words that come to mind when we think of Software Defined Radios, but minimalist guru Peter Parker, VK3YE, reminds us that with little more than an antenna, a diode, a crystal oscillator and a connection to the computer soundcard, you can dive into the world of SDR. 

I've been doing this for some time now, but my receiver uses a 40673 dual gate MOSFET and a universal VXO from George Dobbs, G3RJV.  I've been running mine with the FLDIGI and JT-65 HF programs.  Peter's video alerted me to the charms of SDRadio from Alberto, I2PHD.  This is a very nice program.  Of course, I'm always happy to add a dash of Italy to my operations.  Thanks Peter!  Thanks Alberto! Thanks George!


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

Cliff Stoll DEFINITELY has The Knack! And he Kluges!

 

The Maker Blog has a nice article on Cliff Stoll, the author of "Silicon Snake Oil" and "The Cuckoo's Egg."   I liked Cliff's books and included quotes from them in "SolderSmoke -- Global Adventures in Wireless Electronics."  I was glad to see that Cliff is doing well and still tinkering.  Be sure to check out the video on his R/C fork lift.  FB OM.

I was, of course, very intrigued by the slide showing the symbol of the "KlugeMeisters of America." Can we get a pronunciation ruling from Cliff?  Can we nominate people for induction into the KMA?  

In Spiritu Klugo!  Non Vacuo Sine Glyptum!  Words to live by,  my friends...  Patrick Murphy explains all this here:  http://www.cv.nrao.edu/~pmurphy/kluge_where.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

Ham Radio, the tsunami, HW-101, Tek 465, BITX-20

I know many of you guys have seen this before. And I know that Farhan is tired of seeing it pop up again and again.  But it just appeared on my Facebook page today and I watched the whole thing and saw things I hadn't noticed before:  There's a Heathkit HW-101 (or maybe its an HW-100).  There is a Tech 465 oscilloscope. There is a BTX-20!  

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's Knobless Wonder Minimalist SSB Rig

 

Oh man, Peter Parker has done it again!   As he did with the Beach 40, he has come up with a circuit that will attract a lot of attention.  It is a single frequency SSB transceiver with no knobs (or windows, or menus!) 

Peter Marks recently had breakfast in Melbourne with VK3YE:
http://blog.marxy.org/2013/05/melbourne-meetup-with-homebrew-legend.html
There are some great pictures of the new rig, and the Beach 40.

Here's the message  from VK3YE (to the Minimalist Radio Group) that may
someday be seen as the start of the Knobless Revolution:

Some might reckon that SSB is inevitably too complex to be in the minimalist
class, but I beg to disagree.

I reckon you could build a whole SSB transceiver in 2 days of solid work. I
took a day to build what will be described below up to the stage where it
was receiving & producing a low level SSB on Tx.

Take this recipe:

1. Build the back end of the BitX http://www.phonestack.com/farhan/bitx.html
That is everything to the right of (and including) the Q2 & Q12 stages.

2. Use cheaply available 7.159 MHz crystals in the crystal filter and
carrier oscillator. Keep filter capacitor values the same. Remove L3 in the
carrier oscillator circuit. Use a slightly bigger trimmer in the carrier
oscillator (say up to 50 pF) and wire in series with crystal. Align trimmer
so carrier freq is 7160 kHz.

3. Build a power amplifier stage / relay / LPF as per the Beach 40. Just
the last 2 stages (using BD139s) should be enough. Output maybe 2w.

The result is a 10 transistor / 1 IC SSB transceiver on 7160 kHz. It's
crystal controlled but at least during the day 2 watts to a good antenna
should be enough for people to hear and reply to your CQ calls up to 800 -
1000 km away. Of course you could go a bit more minimalist and remove the
LM386, substituting 1 transistor instead (as per the original Beach 40)
which is what I did.

The main thing that's odd is it has no knobs - no tuning, RIT, volume, RF
gain etc. Just sockets - for mic, phones, antenna and power to feed it what
it needs (Rx RF, Tx audio, DC power) and give what you want (Rx audio and Tx
RF).

It is philosophically different to using any other transceiver. You either
accept what the radio dishes up (frequency, AF gain, mic gain etc) or you
don't. On or off - there is no other state. Take it or leave it. Like a
cat this is a radio that lives on its own terms.

Those used to fiddling with adjustments will find the 'knobless wonder'
transceiver causes them to be at a loose end. Those so afflicted will smoke
more, bite their nails more or eat junk food more. Sometimes elegant
simplicity in radio can be a health hazard - maybe knobless rigs should
carry health warnings.

On the other hand, and in my view this outweighs the above, there is the
aesthetic satisfaction that comes from using a rig that cannot be made any
simpler. Especially if it's a mode, like SSB, that's widely thought
constructionally complex. Plus it takes little in return - the power
consumption will be a fraction of what a commercial rig will demand.

73, Peter VK3YE
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

Stacked Shields -- My Arduino DDS LCD Sandwich

You can barely see the Arduino board down at the bottom.  Above it is a homebrew shield that has the DDS board.  On that shield I also put a female header for a small 16X2 LCD board.   This arrangement avoids the rats nest of wire that often accompanies these digi projects.  This thing had me pulling my hair out yesterday.  I couldn't get the display to work.  After a lot of checking and re-soldering and testing, I concluded the LCD board was bad.  Good thing there is a Microcenter right down the road.  I got a new display and my composure returned.

Mark, K6HX, over at Brainwagon has been encouraging me to continue down the digital path.  Other SolderSmoke friends are wary of this digitization -- one wrote asking "Where is the real Bill Meara and what have you done with him?"

I like the Arduino projects.  This little device certainly demonstrates how you can do things with the digi stuff that would be extremely difficult to do with our beloved analog, discrete component circuitry.  On the other hand, as I was pulling my hair out trying to figure out WHY the display wouldn't display, I came across an e-mail describing Peter Parker's latest minimalist discrete component rig. Why, I asked myself, had I left the happy land of understandable circuits?   Why had I allowed myself to be sucked in by the siren song of Arduino? 

I guess it is good to try something new, to learn something, to get out of your comfort zone.  But excuse me now -- I'm going to fire up my 17 meter analog discrete component rig.  The one with VXOs in both the receiver and the transmitter.  But I'm going to leave the Arduino DDS on -- I like looking at the display.
 
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