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ARTICLE FROM JANUARY 1997 

ORGANIZING A HOMEBREW PROJECT 

by Dave Metz, WA0AUQ

Last week a friend ask, "just how do you get so much done?" He referred to the steady stream of ham radio projects that I seem to be involved with. To me, it seems like I am never getting anything done, yet all around me are finished radio projects. This question and the ensuing conversation led me to putting some thoughts on the subject down. 

I'm going to use one of my latest projects, a 6 meter transverter as an example. After being off of six meters for ten years, I decided to get back on the band. I decided to do it the old fashioned way and build a transverter that is a combination receiving and transmitting converter. I started out only with the idea that this device would take a 28 Mhz signal from my station HF rig and put it on six meters. Other than that, the course was uncharted. 

RULE 1. Be selective and focus on something really important! The first step of doing any project successfully is to be careful what you choose. You can't do it all. No one has enough free time anymore so you have to be careful about how much you take on. It is very tempting to try to do a little of everything and dilute yourself to the point where nothing will ever get finished. 

If it is important to you set some time aside. If you have a minute, you can find ten. If you have ten, you can find an hour. An hour here, an hour there and soon you'll get something done. The key is to be selective in how you use your time. Shut off the TV and plug in your soldering iron. 

RULE 2. Make a thorough study of the subject before starting! I learned this from Thomas Edison. Studying the life of Edison, the greatest inventor in history is very beneficial and I strongly recommend it. One of Edison's secrets was his technique of preparation prior to starting the physical work on a project. 

At the time, Edison had the largest research library in the U.S.! He subscribed to every technical and scientific journal published in the U.S. and Europe. Before starting any research project, Edison made the most complete possible study of all prior research in that area. Before he started his work he knew of all that had been done before him. Most important, he knew where the prior researchers had gone wrong! 

In other words, he eliminated a great deal of work before he even started. You can do the same. The best place to start any ham radio project is the ARRL Handbook, aptly called the "bible of Amateur Radio." This is where I started. Right off the bat, I found plans for six meter transmitting converter. I now had a basic idea of a design in hand. 

A copy of the Handbook should be the first purchase every ham makes. A few hours with it can save you thousands of wasted dollars and hours of time. The Handbook is dense and it does pack a huge amount of information in it. It does take an effort to plow through it. Learn to use the index. When you find that you don't understand something, backtrack to the section on the basic theory. 

Hamfests are great sources of books. I've found stacks of text books, data books and manuals for pennies to a couple of dollars. For basic theory you don't need the newest book. The fundamentals are not changing very fast! The laws of physics are going to stay the same. I've often found it very useful to sit down and reread the fundamentals every once and awhile. 

An observer could also tell whenever I'm starting a new project. You'll see me walking about the house with a book in my hand reading. I do a lot of reading before starting anything new. The more I study, the less wandering the wilderness of ignorance I'll have to do. 

RULE 3. Study the new technology! Read magazines, catalogs and data sheets. After looking through many back issues of various radio magazines and thumbing through my stack of radio parts catalogs a new idea came to my mind. The design I had found in the Handbook had become obsolete. Newer parts (in this case MMIC amplifier IC's) could greatly simplify the design! Amplifier stages with 15 parts could be replaced with stages with six parts that cost less. Plus the complex ten watt P.A. stage could be replaced with a single simple RF power amplifier module (more on this saga later). 

Make use of the Internet. Most of the parts suppliers have web sites. Many of them have complete catalogs of the latest and greatest on line. The best such as National Semi and Motorola have thousands of pages of parts data on line. In the past to learn the specifications on say a new IC you had to first locate in a catalog the proper data book that had the specs in it. 

In those days, if you are the typical ham, you paid $20.00 for the data book, and then you sat back and waited two weeks for it to come in the mail. Now you can get the same information for free in minutes. When you do get the information, start a book on your project. Print off or copy all of the pertinent information and keep it in a note book. This way you have everything in one place where you need it. Your time is limited and you can't waste it tearing the shack apart looking for scraps of paper with notes on them. 

RULE 4. Document what you are doing! Draw out plans as you go. Having ISIS CADPAC schematic capture software helped me greatly with this problem. I began by drawing up some block diagrams of my proposed transverter. At this stage you don't worry about details. You are just trying to get an idea of the organization of the project. What the inputs and outputs will be, the flow and level of signals. That sort of thing. By the way, this approach works well for software projects as well. It is very hard to get somewhere if you don't have a plan on the route! 

Documentation is very important. You are not going to do this all at one sitting. This means you are going to forget things, important things! If you have drawings and notes, you are going to be able to trace back years later your thought process and be able to repair what you built. You think this won't happen? Last year I was contacted by a collector that had just bought at a hamfest a "classic" tube type six meter converter that I had built in 1965! 

He found my call inside the chassis and contacted me by packet. I found my original schematics from 32 years ago and sent copies to him. Someday you will wish you had schematics of everything you do. Keep accurate ones! 

The use of schematic capture software like ISIS encourages this. Draw your schematic. Then keep updating all the changes you make in the design while you make them. Programs like ISIS almost force you to be successful. Since you have to fill in all the parts values, the program makes you think about those values. Documentation encourages clear thinking. Drawing out the schematic encourages you to consider the design carefully. 

Software like ISIS also encourages you to make corrections as you go. Since you don't have to start your drawing from scratch like a you would with a hand drawn one, you'll find it easy to make corrections. If you do this, when you get done you'll have a perfect "as built" schematic for your records. And if your project really works well, you will be able to provide your design to others so they can have the fun of duplicating it. 

After doing the block diagram and some preliminary schematics I had a pretty good idea of the basic structure of the design. Now I could look harder at the "How" of the design. That is, what components would I use and how would I arrange them. 

RULE 5. Check out your (and your friends) junk box! Read those surplus catalogs again. Since this is a ham radio project, money is an important consideration. If you have something, some physical resource, design your project around it. In my case I had a bag of MRF966 GASFET transistors, lots of toroid cores and several SBL-1 mixer modules. This meant that my converter would use the 966 as the preamp stage, the tuned circuits would all be wound on toroids and all the mixers would be SBL-1s. I could have used other components, but those I would have had to pay for! 

Remember that you don't need the newest and brightest parts for your project. My new 220 Mhz transverter will have some 30 year old piston trimmer capacitors in it. Some of the parts came from "under the table" at a hamfest. They may not be the perfect parts, but they will work and that's what is important. 

Organization of your "junk box" is critical. Having the right parts does you no good at all if you can't find them. I just counted, I have 750 little drawers of small parts in my shack. I could use another 120 drawers right now just to do the job right! Time wasted tearing the shack apart looking for a part is time lost from your project. The frustration drains your energy. What was fun becomes a drag. Organize before you start. Keep every thing in its place and you will be amazed how much time it saves you. 

RULE 6. Eat the elephant one bite at a time! Taken altogether my proposed transverter would be complex. If I took it as a series of simple blocks of circuitry, it became much simpler. Very simple in fact. Instead of trying to get an entire transverter to work, instead I concentrated on getting small simple blocks of circuitry to work properly. 

RULE 7. Start with the KEY portion of the project first. That is, the portion whose success everything else depends on. 

For my project the local oscillator was the key block of circuitry. Without a clean local oscillator the rest of the transverter would be useless. I broke the Local oscillator down into three smaller blocks of circuitry: The crystal oscillator, the harmonic filter and the amplifier. Now the whole thing had become manageable. 

RULE 8. Prototype any circuit whose operation you are not sure of. Build your project in small modules. 

For example I started by building a prototype of the crystal oscillator on a scrap of PC board. No, it did not work as expected! My toroid cores were made of a different ferrite than the ones the original designer had used. A couple of coils later, I had a crystal oscillator and I knew how much power it put out. More important, I knew how bad the harmonics it put out were! 

With this knowledge, I could safely design the rest of the Local Oscillator (well pretty much so) and layout a printed circuit board. Naturally my wonderful new oscillator on its new printed circuit board didn't work at all. No problem! By this point you should be humble enough to know that there will be mistakes in your layouts and designs. 

RULE 9. Don't be afraid of making mistakes! Accept that you will have to make corrections. 

After I found the mistakes, I laid out a second board and tried it. After all, small parts are cheap and most of the valuable stuff on the board could be removed and reused. Using the Techniques PC-Blue laser printer PC board fabrication system makes making new boards fast and easy. There is no point in worrying about mistakes when you can make a new better board so easily. 

In the end I found that all of the boards in my transverter had to be redesigned at least twice and in some cases three times. Although I found this to be irritating at times, in the end it all worked out well. It is very important to remember that when homebrewing a project, getting there is most of the fun! If everything you do works the first time homebrewing would get pretty boring pretty fast. 

RULE 10. Keep your energy up! Don't let your project weigh you down. This is a hard one. There always comes that time when it seems that you are not making any progress and you will never get your project done. At that point, don't quit, just set it aside and walk away. That's right, just forget about it for awhile. How long? It could be an hour, a day, a month or more. The point it don't beat your head against the wall till you loose interest. 

When the frustration builds too high, go do something else. I usually keep two or three projects going at one time. When one gets to be a drag, I work on another. I alternate between them (often on the same day!) This keeps me fresh on all of them. There's nothing wrong with set a project aside until the right parts, test gear, money, whatever come available. 

RULE 11. When you get stuck, ask questions! If I have noticed one change for the worse in ham radio it is that hams are very hesitant now to discuss problems or ask questions. OK, lets say you hit a rock. First hit the books again. No answer there? All right use your other resources. Send a HELP message on packet. If you have Internet access try posting on the newsgroups that are relative. Call the ARRL and talk to the technical department. If you know another ham in the area that is doing or has done similar work, ask them. 

The main thing is, don't sit still! DO SOMETHING! Don't fret if you are unsure where to look for an answer to your problem. Learning where and how to ask questions is an art too and one that you can only learn by doing. Do not be afraid of being embarrassed or asking a "dumb" question. The only dumb thing you can do is not ask at all. If someone does respond in a negative manner, ignore them and move onward. 

RULE 12. Finish what you start. Nothing is more discouraging than a bench full of unfinished projects. These mean you have both wasted your time and your money. Finishing a project (and this means the documentation too!) is what it is all about. Anyone can fail, that's easy. Always keep your path to completion and success in mind as you work. If one module doesn't work, back track and try something else. 

I had to do this on my transverter. At first I tried to build my own ten watt P.A. I soon discovered that RF power transistors that I had were specified for 30 MHZ. They did not work well at 50 Mhz as I had been told. This stopped me cold till I read an article on a six meter transverter in QEX magazine from the ARRL technical department. They used a ten watt P.A. module from RF Parts. I wisely did the same! Building the prototype P.A. did not waste my time. Along the way, I learned a great deal about transistor RF amplifiers and impedance matching. 

In the end I had a fine transverter. It works very well and I'm happy with it on the air. I have it completely documented too! Another bonus is that since it is completely documented, I can use it as a starting point for my next project, a 220 Mhz band transverter. This should go a lot faster if I don't repeat the mistakes I made before. 

Summary.Lets go over all of this one more time: 

  • Decide if its important to do
  • Study the prior work of others
  • Make a preliminary simple design, document everything you do!
  • Round up your parts
  • Build in modules! Make one module at a time work.
  • Don't get discourage, ask questions, finish what you start
When you are done, be proud of what you have accomplished! Use it on the air and show it off to your friends an amaze them. Then clean the bench and start dreaming about your next project. 
David Metz, WA0AUQ

davemetz@muscanet.com 

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