OBSERVATIONS FROM SCOTLAND

'Black Box' operators apart, most of us have some basic test equipment and tools. What you might need or want depends on a variety of things, what bands you use, whether or not you build or modify gear for your own use and so on.

A basic toolkit is also a virtual necessity for all and at the most simple level, might consist of a selection or screwdrivers, pliers, side cutters and soldering iron. After a while, you'll want a testmeter and for amateur radio use at least, for a number of reasons, a moving coil meter or good sensitivity (20Kilohms per volt or higher) is much to be preferred over a modern digital multimeter. If you ever have to peak up a tuned circuit, a digital meter is almost useless for the purpose whereas with a simple 'old-fashioned' analogue meter, you can easily see at a glance whether the signal is increasing or decreasing, something that's more difficult to to do with a slower acting digital type. In amateur radio work, you often don't need particularly accurate readings... speed of response of the meter is much more important so the analogue meter wins hands-down over it's digital counterpart.

For the constructor or even someone trying to tune an RF circuit to resonance, a simple diode probe connected to an analogue meter is an invaluable tool. These are simple to make and I'd point the reader to N5ESE's diode Probe page rfprobe for a suitable example circuit.

You'll soon find that your assortment of tools starts to grow exponentially as you tackle more exotic projects. Jeweller's screwdrivers, a good pair of stainless-steel pointed tweezers, a simple cheap headband magnifier and some more specialised pliers are likely to be added to your toolkit.

As to soldering irons, the most common mistake I see is people using an inadequately rated iron to solder connectors, resulting in dry joints or no contact at all! At hone here, I have a 70W iron for large jobs and a relatively cheap (£30) 48W temperature controlled iron for day-to-day jobs on radios. These temperature-controlled irons are a bit more expensive than ordinary types, but far more versatile. Here's the one I use.

This iron allows the operating temperature to be set anywhere in the 300-790 degrees F, a very useful range indeed. In the metal tray on top of the power unit are a selection of soldering bits for different jobs in addition to a small can of 'tip-cleaner'. The tip-cleaner material restores the tip surface to a bright tinned finish with a single 'swipe' across it. In addition, the iron has a grounded tip and the power-supply unit has a grounding point on the rear for an ESD soldering mat or other ESD (Elecrostatic Discharge Protection) device.

The large 65Watt iron is perfect for 'seam-soldering' tinplate enclosures and other large jobs like soldering coaxial cable connectors where the smaller iron would be completely inadequate. Although going from 48 to 65Watts does not seem like a big difference, the added 'thermal mass' of the larger iron means it can handle bigger jobs with ease. I've noticed that if you put a couple of soldering irons in a dark desk drawer, they tend to 'breed' over time! Before you know it, you have a 'family' of soldering irons.

Antex 18 & 25W irons plus headband magnifier.

These two inexpensive smaller irons (ANTEX) are good for general small jobs. The headband magnifier is invaluable for SMD and small jobs and only cost a few pounds (£3 from memory on EBay).

Soldering frequently requires three hands. Sure, you can go and spend money on a 'helping-hands' type device, or you can make a good Scottish one instead with a scrap of some material (I use a PCB off-cut with some emery-paper glued to the underside) on which is glued a wooden spring-peg of the sort your better half probably uses to hold up the washing.

The 'helping hands' is an invaluable construction aid. It can be used to hold wires, small components or connectors steady while you apply iron and solder to the job. In conjunction with the headband magnifier, it's possible to do very neat professional looking work.

Some folks might prefer to bond a clothes-peg to a lump of wood or whatever... be inventive!.. come up with a new design of your own. Mine was made from PCB and emery-paper because I was too lazy to look for the suggested wooden block. I just used a couple of small spots of epoxy resin to attach the peg to the PCB while the emery-paper stuck to the underside stops it from sliding around too much. It may be cheap and nasty, but it saves countless burned fingers.

The Grid Dip Oscillator (GDO) or its more modern FET based counterpart is a very useful item of test gear for the radio amateur. It is little more than an oscillator (frequently with a simple tone modulator) with plug-in-coils and a 'dip meter' (hence the name) that can be used to align tuned circuits, tune aerials, make coaxial phasing line and measure resonance. The oscillator is lightly coupled to the circuit under test and couples some RF energy into it. As you tune around, you get a current dip indicating resonance and the frequency is read off a printed scale. It's very important with GDO's to have the absolute minimum of coupling to the circuit under test because this gives the most accurate result. You can even build a GDO on the kitchen table, should you be so inclined. Have a look at Harry's Homebrew page Harry's GDO for more information on GDO's (or DDO's) The GDO has a veritable multitude of uses for the radio amateur.

The more adventurous radio amateur might choose to buy a frequency meter. These used to be an expensive tool but perfectly serviceable ones such as the RACAL 9000 series often turn up for very low prices. I have a 9913 bought at a rally. These old but excellent DFM's often change hands for a few tens of pounds. Portable DFM's are also available. I have a Hunter FC-130 which covers DC-1.3Ghz in a single pocket sized instrument.

There's a BUT here. Don't go rushing out and buying equipment such as DFM's unless you can identify a need for it. When aligning RF transmit strips or multiplier chains, often you can use a wideband scanner or suitable radio to listen for the desired harmonic from a multiplier chain.

When designing and building radio projects, as well as when using test equipment, you can't get very far without some attenuators. Sure they are passive things, deadly boring and unexciting but very necessary items. While it's nice to have professional grade gear, there's no real need in most cases to have highly accurate attenuators so you can build perfectly good useable fixed or switched attenuators from junk-box parts.

This site Attenuator pads shows simple PI type DIY attenuators for all the common values you'd want. When building attenuators, and in particular for large values of attenuation, isolating input from output is essential. You can do this by building the attenuators on scraps of PCB using good quality BNC sockets and placing metal foil (copper) screens between input and output. Just drill a suitable sized hole to thread the resistor through.

RACAL 9913 DFM with a simple cheap signal-generator sitting on top

The RACAL 9000 series DFM's quite often go for fairly low prices on EBay and at rallies. These are ancient but very high quality instruments that use proper ovened frequency references. I bought my 9913 at the Magnum rally (Irvine) quite a few years ago. It covers DC - 520Mhz, a very useful range indeed. Old yes, cheap yes, but a very useful instrument indeed.

More exotic test gear that could be found in a very well equipped shack include Oscilloscopes and Spectrum Analysers.

The scope I use here was 'salvaged' from a waste skip. It works perfectly despite having had a slightly careless 'previous owner'. It's in good condition and does a great job of work. Never buy a new scope... there's always one just around the corner, either at your local rally or on EBay or whatever. Just check that it works and has an adequate maximum frequency rating for your needs before you part with your cash.

The Spectrum Analyser (or SA) is a specialist item and shows signals in the frequency domain rather than in the time domain, as with a scope. With the SA, you can see RF signals in real-time., spread along the horizontal axis of the tube with their amplitude displayed vertically. For anyone contemplating buying a second, or tenth, hand SA, be warned that you will need to have enough expertise to repair it when it goes wrong ... as it surely will do at some point in time. In short, if you think you can't fix it, don't even consider buying one! How to use a spectrum analyser spectrum_analyser

SA's can be used with matching 'sweepers', signal generators that accurately sweep a frequency band in synch with the SA's tuning. This allows the user to see and characterise, the frequency response of filters, amplifiers and active and passive devices in fine detail. Most of the SA's that fall into amateur hands are in excess of 30 years old and are likely to have faults of various sorts.

The popular but ancient HP141T mainframe and HP8552A or B, IF unit and various RF heads such as the HP8554B (covers DC-1250Mhz), and HP8553B (cover DC-110Mhz) sometimes surface on EBay and elsewhere. The matching 'Tracking Generator) AKA 'sweeper' Model HP8444A (DC-1300Mhz) for use with the HP8554 RF head also can be had at reasonable cost. Among many other uses, with an SA such as this, it's possible to see radio propagation change in real time, when connected to a suitable aerial. To be honest, the SA is overkill for all but the most well-equipped shack. The HP141T I use here has suffered a number of problems, all of which to date I've managed to fix. The tubes in these SA's have a tendency to be 'poisoned' over time by the Epoxy resin used to bond the storage mesh assembly to the front of the tube. Nothing can be done if this happens and your SA is effectively useless. My SA has gone this way recently but I'm very fortunate indeed in that I have a spare tube for it. Do also be aware that any device using valves or CRT's uses lethal voltages. The HP141T uses voltages in excess of 7KV. You MUST be competent to work on this sort of equipment or find someone who is.