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I'm designing a 40GHz RF system that will be operated outside for research. I prefer avoiding conformal coating and radomes to protect it due to cost, complexity, and loss. An alternative I'm considering is no protection, since the acceptable working life is only 50 hours. Also, we can choose to only operate in good weather conditions, without rain or high dust, around 20 Celsius. Does anyone have experience with the lifetime of unprotected PCBs outdoors?

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    \$\begingroup\$ without size, power, and just what would be exposed, and to what, there's not enough info. sometimes a weather forecast is wrong. you can likely afford to at least put it in a plastic bag... \$\endgroup\$
    – Abel
    Jan 19, 2022 at 1:37
  • \$\begingroup\$ Any chance of condensation, e.g., dew? \$\endgroup\$ Jan 19, 2022 at 1:40
  • \$\begingroup\$ If you're building more than one you could gamble on one. Conformal coating can be added later, I think. @Abel Static discharge? I would think a cardboard box would be better because of that. Only 50 hours and no rain. What materials are 40Ghz transparent? \$\endgroup\$
    – DKNguyen
    Jan 19, 2022 at 1:54
  • \$\begingroup\$ To clarify my question, we will bring it outside for up to 100 30 minute missions on days of our choosing. So no dewy mornings or bad weather, unless it's extremely sudden. \$\endgroup\$
    – bob bob
    Jan 24, 2022 at 14:14

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Since you're only expecting a couple of days of operation, it's not corrosion of the PCB I'd worry about. But moisture condensing or accumulating on a 40 GHz circuit and antenna element can certainly affect them.

Possibly the simplest, cheapest protection, that would not affect the radiation pattern, is an inverted styrofoam cup or bowl placed over the circuit board. Low density styrofoam is pretty transparent to RF. Use a big enough cup so that it doesn't come within 10 mm (i.e. about a wavelength) of the antenna portion of the circuit.

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  • \$\begingroup\$ Given that it won't be operated continuously, I'm not worried about condensation. \$\endgroup\$
    – bob bob
    Jan 24, 2022 at 14:20

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