QRP Homebuilder Workshop Ideas
Discussion:
The following text will discuss setting up a QRP workshop with regard to parts and some equipment. Following that is a brief tour of the QRP HomeBuilder workshop.
Junk Box 101
If you are starting your electronics parts collection from scratch it can be very daunting and expensive to get up and running. Below are some suggestions to build a minimal junkbox collection of parts to experiment and build QRP gear with. It is by no means complete, nor should every suggestion be observed as everyone has specific interests and building philosophies.
Catalogs and Parts Stores
First get on the net and get some catalogs sent to you from places like Digikey, Mouser etc. Get the ECG/NTE catalogs too if you can and anything else you can think of to enable you can cross reference parts and shop for good prices. Electronic parts supply or repair houses can often give you their last year catalogs for reference material. Every time I go to a different town, I check out their electronics parts stores. I once bought 1000 0.1uF/50v ceramic caps for 5$. Also, you can find bargain bins with stuff like transistors for 5 cents each etc. You can save a lot buying in lots of 10 or 100 items from catalogs too. Ham fests are another potential source of parts.
Resistors
The biggest variety of any item I carry is 1/4 watt resistors. I have a huge selection but really this is not necessary. You need lots of values like (ohms) 100, 1K, 10K, 100K, 1Meg, 4.7, 470, 47K, 47K, 51, 36, 150, 220 and 3K3. I buy these values in lots of 10-25 of each type and keep them on hand at all times. You can use, substitute, parallel or series these values to build pretty much anything. Additional odd values are purchased for specific projects as they popup. For potentiometers, 10K values can often be purchased for 1 dollar or less.
Capacitors
For RF decoupling, the 0.1 uF ceramic is my main cap, I also keep ten 0.01uF and ten 0.001uF on hand. For audio, 10uF/16v for stage-coupling caps, 22uF/25V for 13.8 volt decoupling and a few bigger value like 44 or 100 uF or greater electrolytics for driving speakers and decoupling AF power amps etc. If you are going to build LC VFO's, NP0 ceramic are mandatory and a few of each value ranging from 2.7 pF up to 100 pF should be kept. Sometimes the 2.7 pF are hard to get so I just get 5 pF values and put them in series. One might get five of 5, 10, 20, 51, 68 and 100 pf values for a start. If you are building VFO's for greater than 8 MHz, you may need more smaller value caps. Some vendors sell very bad NP0 ceramic caps and I have bought consistently good ones from Mouser and Digikey.
For RF filter, tuned circuit, tank or diplexer caps you can use NP0 ceramic or cheap monolithic ceramic caps from Digikey (COG). Silver Mica and other types can be purchased if you can get them cheaply. You need to keep a few in stock such as 470 pF, 150 pF, 100 pF, 68 pF and some smaller value like 10pF to parallel/series with other caps to build certain capacities.
For audio frequencies, I keep some ceramics like .022 uF, but also use polyester and other types. It depends how cheap I can get them and how critical the design is. For audio filters, you should be fussy, for a transmitter sidetone, you can just use ceramic caps etc.
Variable Capacitors
Trimmer caps; You can cheap plastic/ceramic units from Digikey or Mouser. I use DigiKey SG1030-ND a lot. Variable caps for tuning VFOs or tuners can be expensive, Dan's Small Parts has some good ones. For VFO's I prefer ones that go from 4 - 20 pF but any value can be diluted with series and/or parallel caps to limit the VFO tuning range. Some have built in reduction gear which is nice. You can also take apart old broken tube radios for variables. You can get nice double ganged units and remove plates if required.
Inductors (toroids)
You will need only a few toroid cores to get going. For powdered iron cores, you can get by with just type 2 and 6 material on hand . A suggestion would be to get six to ten T50-6 , four T50-2 and a couple of T68-6 for winding VFO inductors on.
For ferrite core toroids, get ten FT37-43 , the workhorse ferrite core. Ferrite beads and other cores such as the FT50-77 are very useful, but not mandatory.
Transistors and Diodes
Get ten MPF102, twenty-five 2N3904 or 2N2222, ten 2N3906 and a few 2N3866. This will get you going. Buy low noise or hotter transistors when you see them on sale or as needed for special projects. For VFO oscillators the J310 is a great part and is cheaper than the commonly used 2N4416. Otherwise the MPF102 is a reasonable part. Get ten 1N4148 diodes for starters.
Wire
See the Ugly Construction page for hookup wire comments. For winding coils, you need # 24, # 26, # 28 AWG enamel magnet wire as a bare minimum. You can buy 1/4 pound spools from stores like Radio shack.
Soldering Irons
For Ugly Construction you really need two soldering irons. A smaller wattage iron for soldering most components and a 75-100 watt iron for soldering certain components such as terminal strips or in tight spots where you are space limited and can only go directly upright onto the copper with your soldering iron tip( not at the usual 45 degree or so angle ). My smaller iron is a 25 watt Weller.
Test Equipment
Opinions vary greatly on this topic. At the bare minimum, may I suggest a digital VOM and a high impedance voltmeter with an RF probe. I also could not operate without a AF oscillator for testing audio stages.
QRP HomeBuilder Workshop Tour
To the right, is the main electronics workbench. Procedures such as drilling and grinding are done at the unseen main shop workbench. Most parts are kept in the 3 compartmentalized storage boxes seen at the back of the bench. Above the bench on the first shelf going from left to right is as follows: The bench power supply which is homebrew and goes from 5 to 25 volts DC with a power rating of 7.5 amps. A built-in voltmeter is seen on top of the supply. To the right of the supply is a large collection of enamel coated magnet wire. To the right of the wire spools is a homebrew high impedance voltmeter and then my AF oscillator which uses a a simple multivibrator circuit with buffer and a potentiometer to regulate output voltage. On the shelf above I keep many parts such as variable caps and the grey central object is a homebrew 10 watt 50 ohm dummy load with RF wattmeter. The black object to the right of the dummy load is an old HEATHKIT high impedance voltmeter. On the top shelf is a towel for the cat to sleep on ( very good helper) and a old Hewlett Packard frequency counter. The display uses Nixie tubes! To the left on the bench is an unseen fan that is always switched on during soldering. Soldering fumes are dangerous to your health, ensure adequate ventilation.
Above is a close-up of the parts cabinets. The cabinet on the extreme right has been with me for 20 years. In the left foreground is a Weller 100 watt soldering gun.
Above right, a close-up of my toroid collection. Note the T68-7 white cores on the right hand side of the photo. Ferrite cores are in the 2 left side drawers. Some pre-wound coils can be seen and are used for rapid construction when time is short.
Below is a close-up of one of the parts cabinets. They are jammed with stuff. The top 2 rows are filled with resistors. I keep 4-8 resistor values per drawer. Most are 1/4 watt.
To the right is a picture of my scope mobile. This is an old tube Tektronix product which is in perfect shape. I have all the manuals as well. The scope is normally kept to the right of the bench. It has four plug-in modules, a single channel preamp, dual channel preamp, spectrum analyzer and differential comparator. This product was made in the late 1960s and is outstanding. On the bottom shelf of the scope mobile is the comparator plug-in module, a digital VOM and a digital inductance/capacitance meter.
To the left is a close-up of my bench power supply. It is over-rated and heavily filtered. On the right hand side is the fuse in its holder. I generally use 2 amp fuses for safety.
To the left is a close-up of the frequency counter. Although old, it is in perfect calibration and working order.
