Some tools are absolutely necessary for building radio equipment. The following short list should be shopped for, before attempting any practical work. These are the bare minimum required to assemble the projects detailed in this book, and may be all you ever need...
We'll discuss each tool in turn, and suggest what to buy to get the best value and utility.
We use soldering irons to melt solder, which is an alloy designed to melt at relatively low temperatures. The solder is allowed to flow over the joint area where we wish to connect one component to another. The actual art of soldering is described in section 007 of this book.
Soldering irons can be bought very cheaply from discount shops; the quality of these will vary from tolerable to unpleasant, but they will be cheap, and will get you started. The power rating to look for is in the range 20 to 40 watts. Anything more powerful will be too large physically, and if the temperature is unregulated (highly likely in a cheap iron), then it will be difficult too achieve a clean soldered joint. Big irons are useful for heavy work, such as antenna work or soldering pieces of PCB material together. Besides the iron, you will need a damp cloth to wipe the tip of the iron on to remove the accumulated flux residue. Better-quality irons have a piece of special sponge material set into a small tray in the stand; keep this damp and wipe your iron's tip regularly.
I use three irons for work at home; a temperature-controlled soldering station, a 100W high-power iron and a small butane-powered portable. The soldering station is good for general work, and mine has a cleaning feature with rotating sponges inside the housing, which retains the moisture the sponges need to work. The 100W iron is useful for soldering pieces of copper-clad together to make cases or complex modules. Larger screening cans are best soldered with a big iron. The gas iron has a very small tip, and I use it for surface-mount devices. It has an integral flint wheel in the cap.
You will need at least one pair of pliers. A pair of snipe-nosed pliers: get miniature 'electronic' types, as what you are working with will be small, and the leads may not be gripped by larger types. A pair of large, engineer's pliers will also prove useful for gripping larger items. One special pair to get if you decide to take your wiring skill to the next stage is the round-nosed plier. These, as their name suggests, have a pair of long, thin conical tips; these are used to curl wire into a ring shape for making 'mechanical' joints. I modify mine to be as versatile as possible by filing one of the tips smaller than the other, to make a wider variety of joint sizes.
Cutters are available in a bewildering array of shapes and sizes. The ones to buy first are electronic side-cutters. These are for cutting thin copper leads on components, but can also cope with light-gauge copper connecting wire. Never use them on steel wire; they'll lose their edge or break. For very fine work, a pair of 'flush-cut' cutters can be added to the kit. If you anticipate cutting heavy cable, such as hard-drawn antenna wire, then a stronger pair will be needed. A farmer's fencing tool is great for this, as it includes a range of functions in the head, including a hammer and a nail-extractor.
Buy just two screwdrivers initially, and add to the range as you feel you need them. The ones you need are a small Pozidrive, and a 3mm flat-blade. Philips screwdrivers are different to Pozidrive; the angle is steeper and they only have four large flutes. Pozidrive tips have an additional four smaller flutes. They look similar, but you feel the difference when you try turning a tight screw. Extra screwdrivers can be bought as needed, a 6mm flat-blade and a larger Pozidrive are sensible additions. If you decide to buy a screwdiver kit which includes a handle and a range of interchangeable tips, then you have lots of options, including hex bits and Torx bits. Be careful about quality; poor alloy choice means that the tips will wear quickly and chew-up your screw heads.
Use whatever knife style you feel comfortable with. Here at G1INF, the favourite is a Stanley blade in a home-made handle. The choice is between fine blades with good access for detailed work, and heavy blades with fat handles for meatier cutting.
The most likely spanner sizes you will need are 5.5mm (M3), 7mm (M4), 8mm (M5), 10mm (M6) and it would be wise to get a selection of larger sizes, or a small adjustable spanner, for working with control spindle nuts. Small kits of combination spanners (ring one end, open the other) are to be found in hardware stores, bargain shops and market stalls. These are ideal for light home use, but be sure you get that essential 5.5mm spanner. Tip - A 5BA spanner works on M3.
Unless you have worked with radio or electronics before, you are unlikely to have seen a trim-tool. They are essential for setting-up trimmer capacitors. It is tempting for a beginner to use a small screwdriver to adjust a trimmer, but you'll soon learn by your mistake. Screwdrivers have a considerable metal mass, and this adds to the capacitance of the trimmer (and the circuit you're trying to tune). The process will be very frustrating, and although possible if you have the time to cut-and-try the over- or under-adjustment, it's far easier and quicker to use the real thing. Cheaply available from electronic suppliers, trim-tools are a tough plastic rod with a tiny piece of hard metal in each end. They do not appreciably change the capacitance, and you can adjust the tuning in 'real-time'. One word of warning - Trim-tools are not tough enough to be used as a screwdriver, so don't be tempted.
A vital first piece of test equipment is a small, cheap, digital multimeter. At the time of writing (2009), these could be bought for around £5 in bargain stores. There are cheaper models, but they may not have the ranges you require. Cheap analogue (moving-needle) meters are rarely worth buying; they are usually too insensitive. Digital meters have a high-impedance buffer amplifier before the ADC, and are very sensitive. A better-quality analogue meter has its uses. You can see trends in the measured value, and for some measurements it simply feels more comfortable to watch a needle swinging.
Minimum specification for a multimeter:
DC Volts ranges 0.5V to 500V
DC Current ranges 100mA to 10A
Resistance ranges 100 ohms to 2M ohms
Sensitivity - 20,000 ohms per volt (20K ohm / V)
Direct current (DC) voltage and DC current are the main parameters measured when testing a circuit. It is useful to check resistance in a number of situations. If you are unsure of a resistor's value, then measuring it with a meter will confirm it. Circuits can be checked (with the power off) with a resistance meter, and items like fuses and connectors can be analysed for faults.
The sensitivity is where many very cheap meters will fall by the wayside. The lower the sensitivity, the more current is taken from the circuit under test. If you apply a low-sensitivity meter to a high-resistance circuit, you will get a false reading, as much of the circuit's voltage will be drained by the meter. [graphic of meter loading]
One aspect of cheaper multimeters is the quality of the test leads. They will break long before the meter gives trouble, so note that both the pictured meters are fitted with home-made test leads. These are easy to make. Red 'bullet' crimp terminals are compatible with standard 4mm test connectors, and are cheap and easy to buy. A crimp tool for applying them should cost less than £3-.
Tools are seen by some as an object of desire in themselves. People collect tools, not because they need them, but because they look interesting, or they think they may one day have a use for them. If you want to amass a toolkit of your dreams, then go ahead, It's part of human nature. However, if you are fastidious about utility, then the tools above may be all you ever need. There are some extra tools worth considering, and they are described next.
If you plan to make printed circuit boards, then a desoldering pump will be needed if you need to repair them. When a device is removed from a PCB, the hole invariably remains filled with solder, making it impossible to fit a replacement device. A desoldering pump is used with a soldering iron to remove the solder, leaving the hole open. They work like a back-to-front bicycle pump; you push the piston all the way into the cylinder until it latches, heat the joint to melt the solder and then apply the tip of the pump to the joint. Pushing the release button causes the piston to fly back under spring pressure, sucking the molten solder up the tip. The solder is collected in the cylinder, and will need to be emptied from time to time. Unscrew the tip carrier, and shake out the solder droplets. Any which remains stuck to the face of the piston can be released with a small flat-bladed screwdriver. Always wash your hands after this operation, as the finely-divided solder powder is easily ingested, and is toxic. There may be local regulations for the disposal of heavy metals, so either take advice from your local authority about disposal, or consider recycling the solder.
I have deliberately left wire stripper out of the list of essentials, because they are unnecessary for low-volume non-commercial wiring. I only have one wire stripper in my radio toolbox, and that is a special one for a particular fine, single-core wire I sometimes use when prototyping digital equipment. I keep wire strippers in my 'commercial' wirer's toolbox, because my clients expect me to use them, and I do. But at home, I have other ways.
There are at least three ways to take the insulation from the end of a wire without using wire strippers. The first, and least recommended, is to place the wire between your teeth and pull. The chances of chipping a tooth are high, and you run the risk of ingesting slivers of wire. Don't do it! Another way is to slice around the insulation with a knife, and pull off the resulting tube of insulation. This works well, but care must be taken not to cut the wire, or your fingers.
The most frequently-used method is to use your side-cutters. Grip the wire with your cutters, with the flat side of the cutters toward the end of the wire, and pull. It takes practice to remove the insulation cleanly, but once the knack is acquired, you won't look back. This method works well with multi-stranded wire, which is the commonest type. It is flexible, due to its rope-like structure, and the strands deform under the pressure of the cutters, so that more of the cut is applied to the insulation. When stripping single-core wire, make a rotating cut with the cutters before applying the pull.
Don't use this method if you are working in industry, as it is not approved by any employer I've met. You will inevitably mark or even cut through strands of wire when you're learning, but practice makes perfect.
In my experience, a cheap pair of strippers will cause more damage than the use of side-cutters, especially in inexperienced hands. Try the side-cutter method, and by all means invest in a pair of strippers if you feel the need. The type popular with installation electricians, which have a pair of jaws with a dozen or so tiny teeth, are ideal for everyday uses. For high-quality work, a pair of separation-jaw strippers will give first-class results. These are approved for use on aircraft and military equipment and are expensive.
As I mentioned in the first paragraph of this section, I keep a special stripper for miniature solid wire. It is specially designed to cut the insulation, and leave the core conductor intact. These, like the separation strippers described above, are not cheap. The one in the photograph has lasted the author for over twenty-five years.
You will be able to do a lot of testing with just your multimeter. Its capabilities can be extended by making add-on modules, some of which are described in the projects section of this book. They will allow you to measure capacitance and radio-frequency power. There are other projects there which don't involve the multimeter; these include the noise generator, audio amplifier and gate dip oscillator. Other items of test equipment which will be useful to a radio experimenter are outlined in section 017, but as they are expensive and complex, they will not be discussed at length. The two main equipments in this category are the oscilloscope and the spectrum analyser; get an oscilloscope if you can, but check article 017 'Radio Frequency Testing' before you buy.
Care of Tools
I possess tools which date back to my apprenticeship, over thirty years ago. They've stayed with me because I've looked after them, and they've looked after me. Storage of tools is important, to keep them from damage (and from damaging people); an old adage - 'A place for every tool, and every tool in its place'. Keep your tools in a dedicated box, or set aside one or two drawers of your desk for them. Keep them clean; wipe them down with a dry (or slightly oily) cloth, and lubricate moving parts when needed. Pliers and cutters need their hinge joints oiled at least twice a year, more frequently if you use them full-time.
A useful way of storing test leads is to coil them individually, and pop them into small ziplock bags. Squeeze the air out before the seal shuts, and they snug down into a drawer or box very neatly without sprawling everywhere and tangling. If you have wall-space, hang them on hooks for easy access.
Instruments need special care. Check the battery occasionally. Some instruments use a tiny current, and the battery can degrade and leak before it is exhausted. Protect meters and other sensitive equipment from mechanical shock; moving-coils meters are particularly delicate, and a little attention to handling and storage will keep them safe. Protect them when storing, tarnsporting or even in use by means of polythene foam cushioning.
Other Workshop Facilities
A good stout bench, desk or table is needed to work on. I know amatuer constructors who cheerfully work on a bureau, wooden tray on the lap and even on the kitchen work surface. There have been designs published in the old paper magazines for special electronic hobbyist's work-stations.
A vice can be very handy; make sure it's well secured to the bench, and that the rear (fixed) jaw is overhanging the edge of the bench. Cupboards for storing equipment and components, small boxes for keeping things tidy, drawer-cabinets for small items. Take time to think how best to arrange your working space, and ask the rest of the household for their opinion!
Think carefully before setting up shop in a shed or other outside structure. Is it dry? Does it freeze? Some devices (LCDs are an example) can be damaged by very low temperatures. Inside the home is best, but an outside shack can be a rewarding retreat if you can keep the temperature up and the damp down in winter. My mentor, Eric G3HTP (SK), kept his station under the stairs; he was quite comfortable, and far enough from the sitting-room not to disturb the family. I work in a lean-to extension at the back of our house, but I have used a metal shed, which made an excellent ground for my antennas.