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Shielded Plastic Box for Antenna Switch and More

shielded plastic box

You can easily build a shielded plastic box with your 3D printer. Just use some aluminum or copper foil tape to create a conductive metal surface. 

Recently, I decided to build a custom switch box to select between my various noise probe antennas, and then route to either my ANC4 noise canceller or AFE822x dual channel SDR. Normally, I use the ANC4 to eliminate local RFI for my receivers. However, I also use the Afedri dual-channel radio for coherent noise reduction or spatial filtering.

A project enclosure is easy to manufacture with a 3D printer. In this case, I needed a box with room for six F connectors on the back, and two switches on the front. The rotary switch selects between four noise probe antennas. The toggle switch routes the selected antenna to either ANC4 or AFE822x. With the plastic printing, it is easy to create holes for connectors or switches.

The box is 60 by 70 by 40 millimeters in size. Design is easy with a CAD program, and fast to print on my Sunhokey Prusa i3 3D printer. So far, so good.

But what about shielding? Normally, switch boxes are made from aluminum. This provides shielding against local interference. Also, aluminum boxes provide a ground plane for connectors, which makes wiring easier.

Since electric currents flow on or near the surface of a conductor, I wondered whether I could use metal foil to create a shielded plastic box.

Shielded Plastic Box – Putting It Together

Looking around at hardware and hobby stores, I found a wide variety of metal foil tapes. These are usually comprised of thin copper or aluminum foil on top of am adhesive base. Many musicians also use this type of foil tape for shielding their guitars and other electronic devices.

In the end, I selected Nashua 330X Extreme Weather HVAC foil tape. This aluminum foil is 3.5 mil or around 0.1 mm thick. It comes in various width. Mine was around 2 inches wide. As you can see in the picture above, I covered the entire inside surface of my shielded plastic box with this aluminum tape. Works well to provide a pretty solid metal surface.

I tested the conductivity with an ohm meter and all was well. The F connectors are all grounded to the foil. Wiring was done with 22 AWG wire between the F connectors and the switches. Keep these leads as short as possible. Here is a document to describe the build in detail, with instructions and pictures.

[sdm_download id=”4731″ new_window=”1″ color=”orange” button_text=”Show Noise Switch Details”]

One last thing. When you are building plastic boxes with connectors and switches, make sure to leave enough space for a wrench to access and tighten the nuts. This requires some advance planning.

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