THE BAD-FI

Another Reminder that Metal & WiFi Don't Mix

Sadly, this is very common. In the following replies to this Tweet, Todd correctly recommends that his customer suspend the AP below all the metal obstructions.

Typically, when we do that we use a piece of all-thread, cut to size, attached to a 4-gang box to mount the AP from. Here's a good example from Jennifer Huber's blog.

There are a few issues here:

  1. The AP being so close to metal (in this case the very beam it's attached to) means that the immediate reflections from the metal start to distort the signal as soon as it emanates from the AP.
  2. The metal below the AP are blocking, AND reflecting that signal.

This all adds up to a poor user experience on the ground. Where the signal is degraded, blocked, and attenuated.

For an idea of how metal affects RF signal I refer you to this excerpt from the CWDP (Certified Wireless Design Professional) Study Guide:

 

“Examine an antenna, and you will find that it is made of metal parts and dielectrics. The metal parts of the antenna do not even have to be touching each other. It should be clear that bringing metal or dielectrics close to an antenna can have a dramatic effect on performance.”
 
Excerpt From: Shawn M. Jackman, Matt Swartz, Marcus Burton & Thomas W. Head. “CWDP Certified Wireless Design Professional Official Study Guide.” iBooks. 

(Click the link to read the rest of the chapter and view the excellent graphic)

So, be aware of where your APs are placed, and what surrounds them. Give the RF some time to propagate before it comes back and slaps that AP upside the head.

:-)