I have a PCB and am looking to make an enclosure for it. I was wondering if I should go with a plastic box or whether I should go with an Aluminum case. Also for better range does the PCB trace antenna have to be sticking out?
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To the extent that your aluminium box doesn't have large holes (relative to wavelength) in it, it will act as a Faraday cage and significantly attenuate any electromagnetic radiation passing between the inside and the outside.
Sometimes, this is what you want. If you are trying to reduce unintentional emissions of your circuit, or reduce noise received from the outside, this is good.
Sometimes, this is not what you want. If your PCB includes an antenna, you probably want to radiate electromagnetic energy, so enclosing it in a conductive box is probably counterproductive.
answered Dec 2, 2013 at 16:44
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\$\begingroup\$ I want the waves to propagate out. So is plastic a better option. Also what steps should I take to see that my range does not drop when I put it inside the box? \$\endgroup\$ Commented Dec 2, 2013 at 16:48
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\$\begingroup\$ @user2578666 anything (even air) between your antenna and the other antenna will necessarily incur some loss. Different materials and different frequencies and different geometries interact differently, and without more detailed information, there can't be a specific answer here. However, people have been putting antennas inside plastic boxes for a long time (see most consumer electronics) and it works well enough, so I'd try it, and see if it's good enough. If not, you can always put the antenna outside the box. \$\endgroup\$ Commented Dec 2, 2013 at 16:52
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\$\begingroup\$ Okay. I think I will go with plastic then. Are there any good sites where I can buy these boxes in small quantities? \$\endgroup\$ Commented Dec 2, 2013 at 16:57
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1\$\begingroup\$ @user2578666, If the big distributors (Digikey, Mouser, etc) don't have something that works, drop by chat and ask again. But be prepared to say which of your requirements you can't meet with what's available from the distro's. \$\endgroup\$ Commented Dec 2, 2013 at 17:07
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1\$\begingroup\$ There are two mechanisms by which the range drops when you inclose the antenna in a box: attenuation and de-tuning (change of resonant frequency). To minimize attenuation, find the box with the thinnest walls and lowest loss tangent of the material (may not be easy to find this info). To minimize de-tuning, try placing the antenna as war away from the walls as possible. \$\endgroup\$– YuriyCommented Dec 2, 2013 at 20:23