Tip: Aiming external antennas

One of the most annoying things when doing WLAN implementations in LPV environments is aiming external antennas. It never fails that when I’m doing deployments, it takes forever to aim the antenna precisely where I want it. This is further complicated by the fact that the antennas are typically in hard to reach places that are 40-100 feet off the ground in some cases. Yes you can spend hours going up & down on lifts/stairs/etc but who wants to do that? Introducing the Antenna Aimer Express (trademark pending lol).

I’ll start off by stating the obvious. This device is a crude way to help get the antenna aimed to the general location your design requires. It is not intended to be the only tool used to set final antenna positioning, merely an assist to help get you to the final location more quickly.

To start the process, you will need the following:

  • 1/2 pieces of plywood – cut to the dimensions of the antenna you are working with
  • Wood screws – length to be determined by plywood thickness
  • Mending corner brackets – used to repair broken furniture, shelves etc.
  • Bungee cords – 6-8″ is a good length to start with (used to secure device to antenna)
  • Green dot laser pointer – can be found on amazon for $30-40 bucks (green is easier to see and usually have enough power for any distance you would mount an external antenna in a venue)
  • Wood cutting device – Jigsaw for me
  • Electric/battery powered drill
  • Measuring Tape
  • Speed Square
  • Sandpaper – to smooth out rough edges
  • String – acts as a security device to ensure the laser pointer doesn’t fall to the ground in case it becomes dislodged from the aiming device
IMG_4398

Figure 1 – Plywood bases

Fabrication Steps:

  1. Take your plywood and cut to fit the overall dimensions of the front of the external antenna. As you can see in the above image, I have two plywood squares cut for a 10″ and 7″ square antenna. (Figure 1)
  2. Measure the diameter of your laser pointer and find a drill bit to match.
  3. Measure your plywood and mark the center of the piece. This will be where the laser pointer is mounted to help locate the center of the antenna beamwidth while aiming.
  4. Drill center hole to hold laser pointer. For a better hold, I recommend drilling a slightly larger hole and wrapping the base of the laser pointer in rubber to allow removal of the laser pointer if desired. I did this to allow me to use the same pointer for multiple aiming devices.
  5. Insert the laser pointer into the center mounting hole. Attach string to laser pointer and aiming device to ensure safety for those that might be underneath the device in case the pointer becomes dislodged. (Figure 2) 

    IMG_4410

    Figure 2 – Assembled Device

  6. Attached mending corners on minimum of two sides to help quickly affix the device to the front of the antenna. Doing this allows you to ensure that the device is attached to each antenna in the same position every time.
  7. Attach bungee cords to mending corner mounting holes and wrap around antenna to ensure safety while using. (Figure 3)
IMG_4423

Figure 3 – Device attached w/ bungee to antenna during use

So what do you with your newly built aiming device? The fun part of antenna aiming of course!

You might be asking, “What do I aim at with this device?” Remember that final placement design work that you did, (you DID do it right? I mean how else are you even to the point of mounting AP and antennas???) simply transpose the center of each coverage cell in your design onto the floor of the venue you are working. If you need help in estimating coverage cell sizes in your design using external antennas check out my earlier blog post. I like to take neon colored post-it notes and place them below. They are usually high enough visibility in a venue that you can see them from the final antenna mounting height. Once you have these placed, use the device to aim the antenna in each coverage cell at the points you just placed.

I like to use my Netscout AirCheck G2 to determine what the actual coverage cell is and provide adjustment data on any fine tuning required based on the actual signal propagation for that antenna beamwidth. After this, I also like to use Ekahau Site Survey during a final passive site survey to verify the coverage meets project requirements.

Hope this helps everyone in their efforts with external antennas! Do you have any tips like this? Feel free to post here, or better yet….GO BLOG!

-Scott

One thought on “Tip: Aiming external antennas

  1. Pingback: Packet Pushers Link Propagation 86 - Packet Pushers -

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