TECH Sunday Build

Seeing radio waves with a light bulb

More from one of my favorite MAKEzine bloggers -- Diana Eng -- This is an excellent way to help one visualize radio waves as you build your DIXIE PIXIE.

... Using a low power amateur radio transmitter and a simple light bulb receiver circuit, we see how radio waves and electromagnetic induction transmit energy and signals wirelessly through the air. We also see how dipole and Yagi antennas radiate their energy in different patterns. Read on to build your own dipole receiving antenna! 

Watch the whole video HERE

Enclosure Idea - PIXIE built inside a 9v battery

For those of us thinking of departure from the now cliché Altoid Mint Can. Here is an alternative from our friends at Hack-A-Day --

... It’s pretty creative to use a 9v battery as an enclosure. That’s what [Osgeld] did when building this amplifier. There are several advantages; they’re easy to find, it keeps a bit of the dead battery out of the landfill, and this method provides a built-in connector for a 9v power source. In this case the circuit is built around a LM386 audio amplifier. It’s glued to the back of a potentiometer and wired up with the other components for a package smaller than a quarter. A stereo jack reside in the side of the battery case with a cable and alligator clips for connection with a speaker. Now the amp can be quickly connect to any 4-8 ohm speaker...

The rest of the Article at the Hack a Day Site.

The Whys & Hows - Dixie Pixie

The "pixie" is a QRPp transceiver, it is a minimalist rig using the minimum components. It is fun to build and has a variety of mods to enhance its performance. Output power is in the range of 250mw to 500mw depending on the transistors. As you would expect from a rig like this it does have its problems and limitations, but there is lots of info on the web regarding mods and fixes for this rig. It can be made in an evening and can be an ongoing project for anyone interested in building and I am sure it will give anyone interested in home-brew QRP projects hours of tinkering time.

In this blog I will capture the steps needed to build the DIXIE PIXIE 2 via Manhattan Style and we will take the time to understand the various parts of the radio.

The PIXIE 2 It is available on the web as an inexpensive kit, my goal here is different, my goal is walk a newbie through through the process of creating the radio from scratch, and not just stuff components into a pre-fabricated board.

In preparing this course I researched the origins of the pixie dating back the former Soviet Union's Oleg Borodin RV3GM  and his "original" design The Micro-80 and the subsequent UK version FOXX Transceiver by George Burt GM30XX featured in SPRAT Magazine, and many others.

Follow this LINK to read about the origins and over 30 year history of this radio, as chronicled by UK's premier QRP magazine SPRAT.

The radio is an example in brevity, every parts in the design works double duty, truly a QRP classic and worth our study. In my design (click the image above) I selected the most FUNDAMENTAL parts, many designs you can find on the web are ... well let's just say "embellished heavily by what whatever components were handy at the time." -- Since we are starting from scratch and you don't any components, let's use the best we can find from some of the QRP's and Electronics suppliers, no need to start deviating too soon, although experimentation is allowed and encouraged, I will try and follow and lead you down the middle path.

In some ways the history of the PIXIE reads like a dime-store spy novel, in addition to the BEHIND IRON CURTAIN and UK versions there are also INDIAN, SWEDISH, GERMAN and dozens of AMERICAN versions, each the design is redone to suite the needs of new groups of builders adjusting for part availability, etc. For example many of the mid 90's US versions featured RADIO SHACK part numbers, well guess what fast forward a brief dozen years later (now - late 2009) and those parts are no longer available at you your local mall outlet.

So if you are new to electronics, new to HAM radio, or an old hand but always wanted dig deeper into how radio really work, here is your chance, book-mark this spot and come on back about once a week or so. I will add more and more layers until we have a  complete working radio.

72 ki4SGU

Design Specification - Dixie Pixie

We are up and running, by now you've created a handful of PADs and your brain is hurting from those IIT Electronic courses (don't worry we wont go through all of them, just the basics of the basics to get you conversant with all of the concepts)


We will be building a 80m PIXIE using a color burst crystal - Why??

-- The crystals are 10x cheaper than other HAM frequency crystals, are available world-wide either new or as scrap in old television sets (see TV Set Salvage as you can see one can practically build the whole PIXIE from one old TV) Also, through some extra ordinary good luck Color Burst Crystals are resonant at 3.579545Mc, which just happens to be in the 80m CW band, and well within TECH license portion of the band, that is right I said TECH.

-- These PIXIEs are not really super-duper DX gear, so making a few local & regional NVIS QSOs with your club mates will be as much we can reasonably expect. -- Later on, you'll have the skills to build another on 30m or 20m QRP rigs for real DX power, but by then you'll understand all of the underlying matters. -- This one, remember is to better understand the HOWs and WHYs of QRP construction and radio design, we will keep simple and cheap.

Afterwards, we will look at changing out the OUTPUT tuned circuits and crystals to explorer to other bands, or even be able to bend the crystal to get more tuning range out it. These radios are notorious for also being wide, a so an active cw and notch filters are already in the drawing board.

A simple 2 CMOS chip keyer, will make the kits more cw paddle friendly, and a PC interface will show us how to integrate our little radios to our computers for QRSS beacon operation. There your little kit with the patience of a saint (at least the patience of a machine) will happily chirp out for months making 250mw contacts with far away lands and you can watch via remote QRSS grabbers.

Go ahead and order a few Color Burst Crystals and hand full of 2n2222 transistors, you'll also need some 10nF & 100nF Caps, an assortment of resistors (330, 470, 1K2, 10K, and 22K and 4M7), and small QTY of 1n34A & 1n751A diodes, you'll need these next week, after the TG holidays.

NVIS and Hope! 72 ki4SGU

BASIC Electronics - LECTURE2 - Resistors

Again, I say ... If you are new to electronics,  and are going to attempt the DIXIE PIXIE experience in the proper context you will need a good level of understanding of electrical principles.


In this lesson you should learn

• What is a resistor
  
• How to identify them by values and colors
• how to measure there values with a meter

see WIKI on Resistors
Here is your second assignment.

LECTURE2 - Resistors

NOTE: If you are starting to follow along after 13NOV2009, don't panic. - Simply catch up at your own pace, although I would not recommended more than one lecture/lab session per day, and never skip the Labs. -- To the entire course see "Additional Support & Study Links" in the BLOG right hand side bar, as "Core - Basic Electronics - Lectures by Prof T.S.Natarajan".


-- Blog Entry 0.3 --

Manhattan Pads and the The Origin of the Term "Ugly Construction"

If you have been following along you have now completed reading most of the links on my site, you've watched a few of the Indian Institute of Technology videos and are now ready to try and actually build something. Albeit, not an actual radio yet, but you are inching to get some super glue stuck between your fingers.

Manhattan Pads - Are not New York City Apartments -- According to the QRP & Amateur and Short Wave Radio Electronics Experimenter's Web Site  

"A reference for Ugly Constructing is The 'Ugly Weekender' by Roger Hayward, KA7EXM and Wes Hayward, W7ZOI published in the August 1981 issue of QST. In fact, it was Wes and Roger who coined the term "Ugly Construction" when preparing this QST article.   

 [The article is available online to ARRL members - LINK]

A big part of the learning of the QST article was Ugly Construction! The term and the bread boarding technique emphasized the fact that there is no correlation between the "prettiness" of a construction project and the way it works. According to Wes, the goal had a couple of corollaries. 'First, people like myself who do NOT have the knack for doing pretty projects can still build successful radios. Second, is that we all need to look at our projects after the fact to discover what it is that really makes them work well. In the case of the Ugly Weekender, the thing that makes it fly is that there is a wonderful ground plane with that PC board material'. Indeed, this transmitter functions very well, especially after you temperature compensate the VFO. Wes also built versions for the 30 and 80 meter bands. This transmitter is a true QRP classic; both as a HAM radio transmitter and because it really promoted "ugly" ground-plane or dead bug bread boarding techniques to the scratch home-brew community." 

OK, Hey but that is UGLY and not Manhattan, Where does that come from? Again quoting from the same QRP site

"Ugly Construction has its variations and the Manhattan Style Construction technique has become very popular. Manhattan or "paddy board" style uses small square or round pads cut or stamped from PC board which are glued copper side up on a large copper clad board which is also placed copper side up. The small pads or "islands"  are used for anchoring non-grounded components. Components soldered to the pads such as transistors or ICs are not positioned upside down like in standard Ugly Construction. Many Manhattan style builders use IC sockets as well. There is a tendency to make these projects look very nice and this is a wonderful ground-plane bread boarding technique for builders who have the time and ability to do this." 

UGLY and Manhattan construction techniques benefits (also Manhattan can be beautiful )

• A huge time and money saver for penny conscious QRPer
• Experimenter can have total control over the design
• Rapid and flexible bread boarding technique
• A superior ground plane
• No custom boards to order from QST or FAR circuits
  
• No messy or dangerous chemicals
• allows for easy re-mods and experimentation
  

You can see a lot of this all goes back quite a long ways and has many benefits. So now you've heard people taking about it, and you are ready to learn the details about it. First be sure and read the fantastic PRIMER "Manhattan Building Techniques by Chuck Adams, k7QO"

other sources for similar PRIMERS (also excellent, but related to only one radio project and therefore less general in scope) see;

• Jason /nt7S Intro Paper for the Willamette Project -- PDF (nice overview of bench-tools & techniques)
  
• Jim Kortge /k8IQY Notes for the IOWA-10  -- PDF  (nice organization & example of more complex project)
  

All done reading, Good! Now we are ready to try it ourselves.

Items required: 

• HF Metal Punch (see text)
• Super glue
• some copper clad board stock (or scraps)
• 25w-35w soldering Iron (See OSE in my Vendor List)
  
• Optional - Digital Multi-Meter

Click on thumbnail pictures to make them larger


In order to make the copper pads the recommended way is to have a Deep Throat Metal Hand Punch available at Harbor Freight (ITEM 91510-2VGA). If you don't have one, I'm sure you can borrow one from one of the other build members -- As for non US builders, please email me concerning a suitable substitution in your country --

 

The various punch sets look like this, one can clearly see it just to the left of the calipers. The punch set is secured to the punch vise via a small set screw. The bigger of the fits under the punch, and the smaller on top (it makes the hole).  My Punch Kit cames with about 8 punch sets of varying sises, the second to smallest works best to make circuits pads.




Here one can see me busy punching away at the copper stock and making the actual pads. I have the larger punch, so the leverage is quite easy on the wrist, the smaller one available at harbor Freight requires a tad more muscle. For all my efforts, I will be rewarded with an easy to build and modify component to build QRP radios with. In my case, as you can see the punch is mounted on a small folding table. Works well enough and was surprisingly stable.



 And here is a close up photo the pad about to be made from the copper clad stock. The punched pads can be seen collecting at the bottom.

I would recommend this simple do-nothing circuit experiment to everyone. Take a few of your freshly prepared pads and play and experiment with the best ways to super-glue (cyanoacrylates)onto a copper board.


This will take the sting out of doing the same later on your PIXIE board, no gluing you fingers to your radio on the first try.

Hey, but wait a darn sprekenzie die Minuten here, we've just glue a copper board to a copper board??! Wont that make a short circuit?? -- Well actually no!  Notice the resistance of my fingers is 27 Mega-Ohms, and not infinity (your results may vary, please don't email me about how to calibrate yourselves to 27MO).





But when I measure from the top of the pad to the ground plain, the resistance is essentially infinity (at least far as my meter is concerned)

My meter showing the measurement, and proving the soundness of the technique to easily, cheaply and electrically safely combine boards, pads and components harmoniously.




Here one can see the soldered component on the two Manhattan pads, once you have mastered this simple skill, one will be able to build anything one can dream of. Therefore, building more and more complex circuits requires one only to repeat these same steps over and over.


If you have completed this step, please drop me an email ki4SGU@arrl.net.

Next time we will build an Audio Amplifier.