Nuts and Volts - March 2015

sided PCB pads) or hot-glued to the ground plane.

Figure 5 shows a typical “ugly construction” example. This is a Hartley oscillator for the amateur 40- meter band around 7 MHz. In fact, I used a telegraph key to turn this oscillator on and off, making a couple of “QSOs” or contacts with nearby hams using the few milliwatts of power (also known as QRP power) from this mighty peanut whistle!

If you are envisioning doing some RF building yourself, an RF prototyping board is a useful workbench addition. You’ll need a large piece of single- or double-sided PCB (at least 8” x 8”) and a thick piece of wood as big as or slightly larger than the circuit board.

Drill mounting holes in the corner of the PCB and attach it to the wooden base with wood screws. This gives you a large surface on which to work, plus the base makes it heavy enough to not be dragged about by test leads and cables. I attached rubber feet to the bottom of my wooden base.

Once you’ve finished (and before each use), scrub the board with a Scotch-Brite™pad to remove fingerprints and oxidation. A swab with some rubbing alcohol will also clean the board of oils or greases. The goal is to have an easy-to-solder surface.

Once you gain a little experience with this type of construction for RF circuits, you’ll find it’s a quick and effective way to prototype even complex RF circuits before transferring them to an actual PCB or building them into an equipment enclosure. NV

March 2015 63

FIGURE 5. A typical RF prototype using “ugly” construction in which ground connections are made directly to the copper PCB ground plane. This is a Hartley oscillator for the amateur