This page will increase in size over time, and may lead to other pages. It comes from a desire to see more hams take up real homebrewing, building radios from scratch.
KR1S Workbench: My new bench, June 2008. Signal and sweep generators, counter, scope, QRP wattmeter, DDS signal generator, power supplies, audio oscillator, and HP 312B selective voltmeter to keep the bench from floating away. And enough parts drawers to keep essential components close at hand. The beige square center front is a ceramic floor tile to protect the bench from burns.
Many hams aren't afraid to tackle the increasingly complicated QRP kits, but few will try to roll their own. An unscientific sampling of replies received to a posting to QRP-L gives some insight. Correspondents cited a fear of failure and a reluctance to spend money on test equipment as primary reasons why they don't homebrew their own radios. So let's deal with those issues first.
This one plagues all humans. I may have more to say about it later, but for now, my suggestion is to start simple, building circuits likely to work without much fiddling. That will give you some experience as well as confidence. Radios consist of many subsections. All of them may coexist on one circuit board, but there's no reason you can't build them separately, getting each one working in turn, and then hooking them together.
Start with a simple power supply. Transformers outputting 16-18 Vac are abundant from surplus dealers (see Marlin P. Jones for starters). In addition to a transformer, you need a bridge rectifier, some electrolytic capacitors for filtering, and an IC regulator chip. I got some good regulators from BG Micro, who also sells other useful parts. If you don't want to build a supply, a simple gel cell battery will do as well. Other good sources of parts:
Here's some information on my bench power supply.
Next up in my book would be a simple crystal oscillator. You can buy inexpensive QRP-frequency crystals from the NORCAL QRP Club and use any of the oscillator circuits in the QRP literature. You could even couple the oscillator to your antenna as a milliwatt transmitter, but you shouldn't, because the output is not filtered and will radiate harmonics. They probably won't bother anyone, but we want to stick to the Part 97 requirements, right?!
Audio amplifiers aren't glorious, but they sure are handy if you build receivers. I would say that 99% of the receiver projects I work on don't become permanent additions to my station. Why build an audio amplifier each time? Here's a schematic of the utility amplifier I built for my workbench.
Yeah, okay, printed-circuit boards (pcb) look pretty and professional, but to some of us, "Ugly" is beautiful! For HF radios you don't need a pcb unless you're using surface-mount (SMT) components. And even then, you can mount them Ugly-style with some care. An alternative is "Manhattan" construction, using little islands of pcb material to isolate components from ground. Too much work for me. We're experimenting here, and Ugly construction works very well.
Elenco multi-point breadboards also work well, even at radio frequencies, and make it easier to swap components like bias resistors while developing a circuit. In the following photo, I was working on a low-pass audio filter.
My workbench is made of laminated one-inch (25-mm) lumber reinforced with 2x3-inch (50x76-mm) lengthwise supports, resting on steel sawhorses. The surface was coated with semi-gloss polyurethane. A 16-inch (400-mm) square ceramic tile protects the surface while soldering.
You could follow the example of this gent from the 1930s and use the kitchen table, but this is not recommended, even if you offer to load the dishwasher. (From Radio News, April, 1934.)
More to come on this, but here I'll list the stuff I use most often.
No argument here, and with a simple diode RF probe it can substitute for an oscilloscope in many places.
I use mine a lot, in conjunction with a frequency counter, but you can also make a simple VFO for testing filters and receivers. I use an ancient URM-25D, bought for $30 at a hamfest.
Very useful item, especially if your signal generator has coarse frequency readout, like the dial on the URM-25 series.
Not essential, but very handy. I use an old Tektronix 2215, 50-MHz scope. It cost me about $150 with one probe. Learning to use a scope takes a little time, but they are so useful, I wouldn't be without it. More to come on this.
This is not as necessary as a scope, but still handy for reading unknown caps and inductors, or checking your work on a hand-wound coil. AADE makes one in kit form that is good enough.
One of these can fill in for more-expensive equipment until you're ready to buy them. If it has a digital dial you can use it in place of a counter to set up a VFO, for example, and it will also serve as a poor-ham's spectrum analyzer to look for harmonics. I use an older Yupiteru wideband scanning receiver and an even older Radio Shack DX-440, also sold as the Sangean 803A. If your station transceiver has a general-coverage receiver, you can use that.
That's relative. All my test equipment put together cost less than my KX1 transceiver. Test equipment good enough for entry-level homebrewing doesn't have to cost a fortune. Once you get some experience you may want to upgrade your equipment, but you should be able to get started for less than the cost of most decent transceiver kits. Good used test equipment holds its value, too.
To help you get started, some excellent advice by Dave Metz, WAØAUQ, on Organizing A Homebrew Project.
I've just discovered Frank, KØIYE's excellent online book, "Crystal Sets To Sideband." Frank operates a 100% homebrew station and his book is loaded with practical tips and suggestions based on his experience building it. Highly recommended.
Another site worth a look is HOMEBREW QRP IS GUD 4 U, compiled by George, KC6WDK, and hosted by Jim, WB5UDE.
I find the "QRP-Tech" group on Yahoo more palatable than either of the QRP-L lists. Check it out here: http://groups.yahoo.com/group/qrp-tech/
More to come!