Simple Homebrew Projects

There is a special pleasure in making a contact with something you built yourself. Homebrewing does not have to mean designing circuits from scratch. A wire antenna, a dummy load or a simple kit gives you that same satisfaction, and each one teaches you something about how radio works.

Here are some proven first projects. Each one is a general description, not a full set of plans. Use a tested design for the details and measure your results.

Soldering Basics and Safety

Almost every project needs solder, so start here. A temperature-controlled iron, a stand, a damp sponge or brass tip cleaner, and rosin-core electronics solder will cover most work. Heat the joint, not the solder: hold the tip against both the wire and the pad, then feed solder into the joint until it flows smoothly.

• Fumes. Rosin flux smoke is a known cause of occupational asthma. Work with good ventilation or a fume extractor, keep your head out of the plume and do not run the iron hotter than you need.
• Lead. If you use lead solder, keep it away from your mouth. Do not eat or drink at the bench, and wash your hands when you finish. Lead-free solder is a good choice if you prefer.
• Burns. The tip is hot enough to burn instantly. Always return the iron to its stand, and never catch a falling iron.
• Eyes. Wear safety glasses when soldering and when clipping leads, which can fly across the room.

A Wire Dipole

A half-wave dipole is two equal lengths of wire fed in the middle with coax. It needs a center insulator, two end insulators, rope and something to hang it from. It works well, costs little and is easy to understand.

The usual starting length, in feet, is 468 divided by the frequency in MHz. For 14.2 MHz, that gives about 33 feet in total, or two legs of about 16 and a half feet each. The Antenna Length Calculator does the math for any frequency.

The formula is only a starting point, because height, nearby objects and wire type all shift the result. Cut the wire a little long, hang the antenna and check where the SWR is lowest. If the lowest SWR falls below the frequency you want, the antenna is too long, so trim equal amounts from both ends and check again.

A choke at the feed point helps keep RF off the outside of the coax. Above all, put the antenna where it cannot touch a power line, even if a support breaks.

A J-Pole for 2 Meters

A J-pole is a half-wave vertical fed at its bottom end through a quarter-wave matching section. The result looks like the letter J. It gives a handheld or mobile radio at home a real boost over a rubber duck antenna.

One popular version is made from ladder line or twinlead and rolls up for travel. Another is made from copper pipe and fittings and lasts for years outdoors. Both are small enough on 2 meters to build on a kitchen table.

Many tested designs are published, so pick one and follow its dimensions closely. The feed point is usually adjusted along the matching section for the best SWR, which is much easier with an analyzer. A choke on the coax just below the feed point often helps.

A Dummy Load and a Ferrite Choke

A homebrew dummy load is a good lesson in how resistors add up in parallel. Twenty 1,000 ohm resistors in parallel make 50 ohms. If each one is rated at 2 watts, the set is rated at about 40 watts in theory, so use it at low power with short transmissions.

Use carbon film or metal film resistors, not wirewound ones, which act like coils at radio frequencies. Keep the leads short, often by mounting the resistors between two small plates of copper-clad board with a coax connector on one. Check the finished load with an analyzer; it should look close to 50 ohms across HF.

A ferrite choke is even simpler: wind a few turns of coax through a ferrite core, or snap clamp-on ferrites over the cable. Which material and how many turns depend on the band, and Ferrites and Common-Mode Chokes explains how to choose.

A Code Practice Oscillator and a QRP Kit

A code practice oscillator is a small audio tone generator with a jack for a key and a speaker or earphone. Many versions use a single timer chip and a battery, and the whole thing fits in a small box. It is an ideal first soldering project and a daily practice partner. See CW, CW Keys Explained and the Morse Code Tool to go with it.

When you are ready for something bigger, a QRP kit is a classic next step. ARRL describes QRP as 5 watts output or less for CW, or 10 watts PEP or less for SSB. Many kits are simple CW transceivers or receivers sold by small makers and clubs, with clear manuals that teach as you build.

Before you build a transmitter, make sure your license covers that band and mode. The Privileges Tool shows what you can use.

A Powerpole Power Panel

Anderson Powerpole connectors are widely used for 12 volt power in ham radio, especially by emergency groups. A small distribution panel, with one heavy input and several fused outputs, tidies up the shack and makes it easy to run everything from a battery.

• Put a fuse on every output, sized for that device’s cable, and a main fuse close to the battery or supply.
• Use wire heavy enough for the total current, and keep red for positive and black for negative.
• Crimp the contacts with the proper tool. If you solder them, keep the solder inside the wire barrel so the contact still seats.
• Many emergency groups use a standard way of assembling the red and black housings. Ask your local group which layout it uses and copy it, so your gear plugs into theirs.

For batteries and portable power, see Portable Amateur Radio Power.

Test, Then Use

Every project ends with a check. Look over solder joints with a magnifier, measure for shorts with a meter before applying power, and sweep antennas and loads with an analyzer. A few minutes of testing saves a lot of puzzling later.

If you get stuck, take your project to a club meeting. Someone there has built one before and will be glad to help. For the instruments that make testing easy, see Test Gear for the Shack.