Thursday, October 1, 2015

Simpleceiver ~ Part 2

The Art of Homebrewing, A Disciplined Process!

Addendum 10/2/2015~ Schematic
Having spent most of my working life in the aerospace industry I can tell you first hand that having disciplined processes is paramount to producing high reliability products. It is only through disciplined processes that one can achieve consistent outcomes. That same logic applies to our wonderful hobby. Randomly  tack soldering a bunch of parts and wires could be successful but that most likely is a rare exception rather than a consistent outcome. Thus having a disciplined process for approaching homebrewing will move you way up the success curve.
The very minute someone mentions a process there are all sorts or rigorous rules that are envisioned and that not is not what is meant. A disciplined process in our context is more so  an organizing effort that enables doing tasks in a logical, sequential and measured manner. We are lucky for today with just a few mouse clicks we have much of the information needed to build our disciplined process and be successful at homebrewing a radio project.

Every process must start with two critical pieces of information: where to start and the desired end state. This may sound simplistic but often the failure to accurately identify these two pieces results in a major disaster. Starting by turning on the soldering iron and 'welding" parts together says it all. You will often hear me repeat lighting up the iron is one of the last steps in the process.

  • Deciding on what project is a really good starting point --and start with a small project. The Michigan Mighty Mite, 80 Meter CW transmitter is a great example. About 12 parts including the Low Pass Filter and the level of complexity is ideal for a first project. One creative ham lacking the tuning capacitor built his very own cylindrical capacitor from two beer cans and some electrical tape. So don't overlook the possibility of homebrewing all of the parts. Another might be building a simple dipole antenna. Or maybe a crystal set. But don't light up the iron yet --- there is much more to do.
  • Information gathering is the next step. Simply downloading a bunch of information on to your computer, tablet or Smart Phone without a thought about how to organize the data is a huge mistake. In the future you will want to retrieve the data you collected and having a process to store and retrieve data is key. I have several file folders on my computer where I organize my data. These include: Specification Sheets (pin out data, power ratings for various devices, etc.), Receiver Projects, Transmitter Projects, Transceiver Projects, Design/Technical Notes, Antenna Projects and Software.
  •  Start by "Googling" Michigan Mighty Mite and do a similar search of You Tube. You will be absolutely amazed at how much information exists on this project. Do overlook the SolderSmoke Blog and other blogs that are searchable. Save the information in the appropriate folder.
  • Find, beg, borrow or steal the following publications: Solid State Design for the Radio Amateur (Hayward), W1FB Design Notebook (DeMaw), QRP Power (ARRL). You can bypass the ARRL Handbook and EMRFD and this is just a personal opinion. While these two publications are good in their own right, the ones suggested are more practical in nature and written for those just starting out. There are two quarterly publications that are useful: QRP Quarterly from QRPARCI and the SPRAT from the GQRP club. I am more inclined toward these magazines more so than QST because of my bent on homebrewing. If you wanted to read about the zillion radio contests or see a review on the latest $12000 radio then by all means jump to QST. In particular two of recommended publications (Solid State Design and W1FB Design Notebook) form the basis of much of the background circuits that are used in the Simpleceiver.
  • Download and install the following free software. EZNEC for antenna modeling, LT SPICE for circuit simulation and Arduino IDE (you will need this later). We have a favorite single transistor amplifier circuit that has been used as an audio preamp and as a microphone amplifier. We have simulated that circuit using LT Spice and are presenting that below. Mouse clicks and no soldering irons were used to evaluate the circuit properties. This is the real power of the software as it lets you run various cases so that you can optimize the performance. I found a "notch" in the output and this was fixed by adding a larger size bypass capacitor.

The simulation software not only gives you a quick look at circuit performance but also enables a bit of tinkering to perhaps stretch the Frequency Response or increase the Power Output. Mouse clicks not soldering irons (at least at this stage) is the order of the day.

Stay tuned for more information on the Art of Homebrewing Process.

Pete N6QW


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