Monday, April 25, 2011

My magnetic survey rig

This is my site survey rig.  Most of it came from the shelves of our local Ace True Value hardware store.  After some trial and error, I came up with the solution that works for me. 

The flexible painter's handle was probably the most difficult thing to find - I shopped around for weeks until I found "the perfect" one.  I wanted something that was flexible, and wanted to minimize the RF attenuation cause by the metal.  So I chose the metal flexible handle and a fiberglass painter's pole.

I wanted to make something that I could use by myself - so I bought a "rare earth magnet" on eBay and taped it to the flexible portion of my survey pole.  This allows me to walk up to any metal ceiling grid and have my survey pole stand up by itself while I do my thing.  Turns out one magnet was making me uncomfortable, so I taped another on there and both of them side by side definately do the trick.  Just enough to hold it there, but not enough to pull down the entire ceiling.  Your mileage may very.


  1. Any electro -MAGNETIC interference found to effect the radio waves?

  2. Interference - not yet. Signal seems to propagate normally. We had to temporarily mount an 1140 about two years ago in a basketball arena. Since the concourse was built like a battleship (steel everywhere) we decided to try mounting the 1140 with smaller rare earth magnets. Four little magnets held the AP to the ceiling steal quite well. We attached the mounting bracket to the AP and the magnets to the back to the bracket and it worked just fine. After the game, we removed the AP. We've since mounted the APs under the wood basketball court, but the magnetic mount did get us out of a pinch.

    About ten years ago we were building a wireless WAN with Cisco 340 series 802.11b bridges. Mostly point-to multi-point links, a yagi at the endpoint and an omni in the middle.

    In one case I needed to set up an omni- directional antenna atop a water tank - the kind that are 167 feet tall and look like an egg on a golf tee. I was not allowed to weld or drill into the "egg" itself, so I opened the top hatch and stuck one of these to the top of the tank:

    I had modified it to hold a 2.4 GHz omni, connected the LMR-400 and ran it down the inside of the tank and supported the cable down to the base. That antenna radiated normally also.

    I encourage everyone else to chime in just in case they've seen anomalies due to magnetism.