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Chapter 6: Technology

RF Absorption of Polystyrene Foam

Dear Dr. SETI:
Do you happen to know how much RF polystyrene foams will absorb at L-band frequencies? I know that most PVC materials, due to additives, are not RF transparent, but what about polystyrene foam?

Marcus, Canada

The Doctor Responds:
I can't answer that question, Marcus, but I can tell you how to find out. Cut a block of the foam in question, and put it in the microwave oven for about a minute. If it gets warm, it's absorbing RF. If it's cool to the touch, it's RF transparent. (Put a cup of water in the microwave oven with the foam block. It's supposedly not good for the magnetron to run the oven without a load.)

Marcus Reports:
I placed a chunk of standard DOW-Corning pink styrofoam insulation, in 1.5" thickness, alongside a glass of water in the microwave for 60 seconds on high-power. The water got hot, but the styrofoam stayed at ambient, except for a small section that was right next to the glass, which was just barely warmer than the rest of the chunk.
I'm thinking this will be just fine for use as insulation at 21cm.

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