Foil Prototypes

If you like to build RF circuits, you know that you can't usually use those white prototype boards (you know, the kind you shove wires into). These boards have enormous capacitance and other undesirable characteristics. They are OK for simple circuits, but RF circuits need something better.

PC boards are great (wide, thin conductors are good for RF). But who wants to cut a PC board just to try something out. Also, this discourages experimentation since you have to do a lot of work to change a PCB.

Here's an easy way to build simple RF prototypes. First get a shoe box top. You can easily cut holes in it to hold variable capacitors, SO238 connectors, and other panel mounted components. Next, use copper foil tape from any stained glass supply house to form conductors like you would on a PC board. The tape is dirt cheap, has an adhesive backing, and is designed to take heat. You can cut the foil with scissors or an X-Acto knife, and press it down to the shoe box top.

Solder your components directly to the foil. Very small pieces may not have enough adhesive to resist the pull of the component leads, but you can usually push it back down if that is a problem. Any where you want the foil to connect to another piece of foil, solder the overlapping pieces to make sure you get good electrical connections (the adhesive isn't conductive).

If you want to make changes, heat up the solder joints and remove the parts in question. Then just rip up the foil tape. No big deal.

I've built a couple of transmitters using this technique. I bought 36 yards of 3/16" MasterFoil Plus tape (made by VentureTape) for less than $5. This appears that it will last me for years. Don't waste your money on the kind with the extra color backing. Get the cheap kind. You can get thinner foil, and I keep hoping to find time to try some with some ICs. The .1 inch lead spacing is too close for 3/16". Let me know if you have any luck.

Here's a bad picture of one of my transmitters