Monday, October 5, 2015

Simpleceiver ~ Part 2 Continued

The Art of Homebrewing --- Continued

In our previous post we outlined some "homebrewing get ready" actions such as setting up a filing systems and securing certain publications. We now want to continue that journey.

The Hardware Part of Homebrewing

  • Homebrewing tools and equipment can make or break project and so often even basic test instruments have not been secured and the question I frequently get "How do I know it is working?" You will only know if it is working is by testing and if it is not working then a troubleshooting  procedure needs to be in place.
  • Basic tools include a good quality pair of needle nose pliers,  wire cutters (nipper), screwdrivers (various sizes of flat head and Phillips), a small adjustable wrench, flashlight, and exacto knife. Add to that a pair of forceps and tweezers. Also don't forget a suitable workspace with good lighting and last but not least a temperature controlled grounded soldering iron.
  • Test equipment is a must! Some can actually be homebrewed and works just as well as commercial units. A Digital Voltmeter (DVM) is a basic item of equipment needed in the shack. There are all kinds and varieties and some have functions beyond measuring resistance, voltage and current. Some will check transistors and diodes, while others can also measure frequency, as well as inductance and capacitance. Another tool which used in conjunction with the DVM is an RF probe which contains only 3 parts and thus easily homebrewed. An SWR bridge is another handy tool for checking RF output. Don't forget the dummy load which can be made from twenty 1K Ohm 2 watt non-inductive resistors which are connected in parallel. Effectively you have a 50 Ohm, 40 watt non-inductive resistor "dummy load" which is perfect for testing QRP transmitters.
  • Moving on to more sophisticated test equipment entails being able to see and accurately measure your signals. The two most frequently used items are an Oscilloscope and Frequency Counter. Many of the current crop of Digital Storage Oscilloscopes have a built in counter so it is a two for one. In the interim and in lieu of an oscilloscope (you will eventually need one of these) and frequency counter (you eventually will also need one of these) a General Coverage receiver with a BFO becomes a critical piece of test equipment. Many of these can be found in the $50 range. use of such a receiver enables listening to say an oscillator (verifying it works) and secondly it will tell fairly accurately the frequency of oscillation --it is a two for one test.
  • A "Junque Box" is one of the most critical pieces of the Homebrewing Art and having the right parts at the right time enables rapid prototyping as well as saving money. In time the seasoned homebrewer will find that buying a single part costing 15 cents often results in a shipping charge of $6.50 USD. But you can buy 100 parts for the same shipping cost. There is a message here and that is "buy in bulk". Most circuits we use tend to have common resistance and capacitance values ( such as 100 Ohms, 1 K Ohm, 10 K Ohm, 10 NF, 100 NF, 10 Ufd, 100 Ufd) buying these in bulk is a good start. The same for solid state devices such as 2N3904, 2N3906, LM386, etc. The Simpleceiver will use JFETS (J310) and I recently purchased a 50 piece quantity for 16 cents each and with shipping was less than $10 USD --that is 20 cents a piece delivered in my hand. One of the auction sites recently had a listing of 1200 pieces (20 pieces each of 60 resistance values) of 1% resistors for $6 USD. True it will take 3 weeks for shipping but at that price -- 1/2 cent each --it is worth the wait. Ferrite cores such as the FT 37-43 are used virtually everywhere from homebrew double balanced mixers to RF chokes. The Toroid King has amazing bargains on these cores. Diodes such as the 1N4148 bought in bulk can be had for 'pennies a piece" and these are used literally everywhere from homebrew double balanced mixers to "snubbers" on relay coils as well as their intended use in diode switching.
  • Enough of the boring but vitally necessary stuff and I will end here. 73's Pete N6QW