WiFi antennas are everywhere …
Hotspot Antennas – providing Internet Access
Client Antennas – receiving and transmitting to Hotspots or Access Points
* Gain in an antenna is gain in one plane or the other (horizontal, vertical) … A typical Omnidirectional Antenna achieves gain in a supposedly desired direction as apposed to in other areas where signal is usually not needed (or where signal doesn’t need to be received from.)
An omnidirectional antenna achieves gain by specially desgined antennas that pull in the “beam width” in the vertical plane so that send/receive signals are not wasted above and below the antenna (how much determined by the vertical beam width) where they are typically not needed. But what if you need to cover above and below? Why would that be?
We’ve noticed in the past with topside WiFi antennas that in some conditions it’s possible to miss the Access Point that you are trying to connect to. And example of this that I remember was a yacht docked behind a house. The antenna was up pretty high installed on a radar arch of a yacht. The Access Point was inside the house … no special antenna … just the built in antenna on a commodity wireless access point. The access point was on the floor in a bedroom. The boat couldn’t reach its signal. Moving it up on a table top made a difference! It brought the access point and the boat antenna beam widths into their respective paths and it starts working.
But this can also happen with Public Hotspots – depending on their construction. Did they install their antennas as omnidirectional? Are they installed up high? And are there obstructions between the boat and the antenna (especially metallic structures) ?
On the Hotspot or other access point side – it is possible to use too high gain of an antenna and leave a hole in the doughnut of the signal around the antenna. If a boat were too close to the antenna it could be in a “dead spot” a black hole so to speak. Hopefully the marina or dock didn’t do this … or installed enough antennas to fill in all the needed areas.
L-com described this nicely, although on a smaller scale (a Cafe outdoor area) on http://www.l-com.com/content/Article.aspx?Type=N&ID=10213. You can see how the signal gets flattened out in the vertical plane … but also how a hole develops nearer to the antenna. Sometimes you also have to consider WiFi Clients that are closer in and maybe below the antennas signal area.
The same kind of thing can happen with access points inside of a boat. They are often installed in overheads … and depending on the antennas in or on the access points and their orientation … it’s possible to not be sending sufficient signal (and reception) where the people are … where the WiFi Clients are.
Some more advice was found here http://compnetworking.about.com/cs/wirelessproducts/qt/locate_aprouter.htm for Wireless Access Point / Routers.
Alan Spicer Marine Telecom
+1 954 683 3426
communications @ marinetelecom.net