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I am designing a PCB including a GPS module. I am using the Locosys LS20031 which has a antenna mounted on it. The module is mounted on the board with 1" plastic studs and a connector connects it to the PCB . The question is if it's good/wrong to lay a layer of copper on the PCB area underneath the module. Will it reduce the antenna gain/sensitivity? It's better to put a keep-out area instead of copper?

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It is typical to avoid placing any copper underneath the GPS antenna for the reasons you stated. You should be careful routing anything below the GPS module because it may leak and cause interference. Route them as short as possible. The module itself would have a ground plane if it was needed.

Looking at the datasheet of the product I can see a hint that in their reference design they removed all copper layers below the antenna, as they should have.

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  • \$\begingroup\$ I would like to note, when using a module you really just should follow their suggestion. The may have an internal ground plane for the antenna and a ground plane below it would have no impact or they might design for the absence of a ground plane. For a black box module you need to know what the module is expecting. \$\endgroup\$ – Kortuk Feb 21 '13 at 21:33
  • \$\begingroup\$ @Kortuk: You're absolutely right. Unfortunately the manufacturer made a terrible job of providing any kind of RF layout information. \$\endgroup\$ – Gustavo Litovsky Feb 21 '13 at 21:36
  • \$\begingroup\$ I was just point it out because you started explaining to never put one, then checked the manual. I would suggest to someone checking the design guide, asking, and if all else fails, build both and see which works better. If they only are one offing, build without, then stick some copper to teh back and see if it helps manually. \$\endgroup\$ – Kortuk Feb 21 '13 at 21:37

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