Timeline for Why does my GPS and Wi-Fi work inside a sealed copper clad box?
Current License: CC BY-SA 3.0
17 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 4, 2017 at 11:26 | vote | accept | tomfanning | ||
| Jul 4, 2017 at 11:24 | comment | added | tomfanning | @Sam that (continuous solder joints, no holes, no penetrations) would be an interesting experiment to see if the Pi totally disappears. The primary aim of course is to stop the Pi from crashing in near field of a 5W 144MHz transmitter - it's probably actually advantageous for my design to be leaky at microwave frequencies but well shielded at VHF :-) | |
| Jul 4, 2017 at 9:42 | comment | added | tomfanning | @user287001 yes absolutely :-) | |
| Jul 4, 2017 at 7:57 | comment | added | Andrew | Keep in mind that shielding for VHF FM (~100MHz) is very different to shielding for 1.5 or 2.4 GHz. A gap in the shield which allows GPS or WiFi through could easily be small enough to stop the FM signal. If you want to test shielding at 100 MHz test at 100 MHz not 15-25 times higher frequencies. | |
| Jul 4, 2017 at 3:57 | answer | added | analogsystemsrf | timeline score: 4 | |
| Jul 4, 2017 at 2:34 | answer | added | Evan | timeline score: 3 | |
| Jul 4, 2017 at 2:30 | history | tweeted | twitter.com/StackElectronix/status/882063948580880384 | ||
| Jul 4, 2017 at 1:06 | comment | added | user136077 | Are you sure that they work all the time, not only when you open the box to see? | |
| Jul 3, 2017 at 22:58 | answer | added | Glenn W9IQ | timeline score: 2 | |
| Jul 3, 2017 at 22:31 | comment | added | Sam | Judging by what I've seen with regards to how high-end RF gear is shielded, I'm betting that if you had a continuous solder joint along all edges including the lid forming a totally sealed box, then the PI should drop off the face of the earth. You've got a large cut-out around the... HDMI? connector, that'll leak some RF too possibly along with the power cable unless you use feed-through capacitors and some ferrite beads/chokes. WIFI needs less that a trillionth of a watt worth of signal strength to run while GPS can get by on a million times less than the WIFI. RF shielding is hard ;) | |
| Jul 3, 2017 at 22:29 | comment | added | user57037 | Yes, it is important that the lid make contact in multiple places. Basically, the gaps in a faraday cage should be small compared to a wavelength. 2.5 GHz is 12cm in free space. 5 GHz is 6 cm in free space. I would be shooting for good contact every 1cm or so. Also, there is a pretty large square hole. You may want to try covering that also, if it is operationally possible. Or reduce the aperture to the minimum, and provide contact between faraday cage and connector outer shell if the connector is needed in use. | |
| Jul 3, 2017 at 22:16 | comment | added | tomfanning | Fair comment. I'll experiment more on the bench. | |
| Jul 3, 2017 at 22:11 | comment | added | marcelm | I'm not sure, but maybe it matters if the lid makes good electrical contact along the entire edge of the box. If you just place the lid on there with the thin wire, it might only make good contact at that one wire... | |
| Jul 3, 2017 at 22:04 | comment | added | tomfanning | Done, and yes, definitely. | |
| Jul 3, 2017 at 22:01 | history | edited | tomfanning | CC BY-SA 3.0 |
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| Jul 3, 2017 at 21:52 | comment | added | user57037 | Please post a picture of the box. Are you sure the top of the box makes electrical contact with the rest of the box? | |
| Jul 3, 2017 at 21:49 | history | asked | tomfanning | CC BY-SA 3.0 |