WiFi Signal Strength with Raspberry Pi 4 Cases

Following a comment from Geir on a previous blog post, where he asked if the metal enclosures which may help assist cooling of the hot Pi 4, could impact WiFi signal strength.

Whilst I only have a small number of different cases to test with. I’d wanted to follow on from my post looking at the impact on cooling from different cases by examining their impact on WiFi signal strength.

Bluetooth testing is out of scope.

Test Environment

My home is probably an atypical setup, with the home WiFi coverage provided by 4 dual (2.4Ghz & 5Ghz) access points. 2 x Apple AirPort Express (802.11n 2nd generation), 1 x Apple AirPort Extreme (802.11n 5th generation) and 1 x Apple AirPort Extreme (802.11ac). This setup came to be after eventually deciding to standardise on one manufacture to aid with device roaming between AP. I’d like to replace this with some Ubiquiti PoE access points at some point in the future, but that’s for another day.

Each Pi test configuration was positioned in the same place, tests were then conducted as close together as practically possible to avoid influence from atmospherics and other external sources

Testing method

With the Pi 4 housed in each enclosure, connected via both WiFi and Ethernet. I run an ssh session into the Pi and use the command: sudo iwlist wlan0 scan to list all the APs the Pi can currently see and record the WIFi signal strength of each of my APs the Raspberry Pi 4 can see from where it resides on my office desk. The command is repeated 5 times for each test configuration.

There are other APs visible to the Pi from neighbouring houses, but we’re not going to worry about those here.

Test Results

Measurements of WiFi signal strength use dBm (0 to -100), closer to zero is better. A simple description of WiFi signal strength can be found here.

Access PointMake/Model2.4 GHz
Channel
5 GHz
Channel
AP1Apple Airport Express (802.11n 2nd Generation)136
AP2Apple Airport Express (802.11n 2nd Generation) 644
AP3Apple Airport Extreme (802.11n 5th Generation)11108
AP4Apple Airport Extreme (802.11ac)836

Note: AP1 is approximately 1m away from the Pi under test, under the desk the Pi was sitting on.

I will be moving either AP1 or AP4 to a different 5GHz channel, they are both currently on “Auto” setting for 5GHz channel selection.

2.4 GHz WiFi

The first graph shows the averages from the tests for each configuration. The second graph shows all the measurements, to highlight where some configurations had patchy signals, not getting reading from an AP for all 5 test runs.

2.4GHz WiFi performance
Click to enlarge
2.4GHz WiFi data
Click to enlarge

5GHz WiFi

The first graph shows the averages from the tests for each configuration. The second graph shows all the measurements, to highlight where some configurations had patchy signals, not getting reading from an AP for all 5 test runs.

5GHz WiFi performance
Click to enlarge
Click to enlarge

Summary

  • Metal enclosures of any kind have a measurable impact on WiFi signal strength.
  • The generic aluminium case performed the worst, with poorer readings across all APs.
  • 5GHz signal strength on the Pi4, on the whole, is worse than 2.4GHz.
  • The plastic cases don’t have a significant impact on WiFi performance, but the Pimoroni Pibow Coupé 4 case performs the best of these. possibly due to the plastic standoffs raising the Pi a little higher off the desk.
  • Of the metal enclosures, the FLIRC cases performed the best. Probably helped by having a plastic base.

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