These antennas narrow your RF pattern to assist your signal acquisition:
They are similar in the RF pattern they produce and could be a great way to select a particular tower when a omni antenna just won't provide the range or signal you need for a good connection
You can see by the following signal radiation graphs how directional they are:
Of the three, the Grid has a much narrower horizontal pattern. This antenna has exceptional range in LOS (line of sight) applications. It can also help you direct your signal acquisition attemps to a particular area or tower.
In a earlier post I talked about how a Omni antenna has a 360 degree pattern. I have a Wilson Trucker Omni on my roof. Lately, for whatever reason, I started acquiring the signals from either two towers or two sector antennas on that tower at once. This was really detrimental to my download and upload speeds. As you can see by this screenshot packet errors were high and the DRC was not optimal.:
I decided rather than wait for Sprint to fix it I would try something on my own. So I purchased a panel antenna and 25 feet of LMR-400 cable and tried to "target" my closest tower. Here are the results after doing so:
The difference was instantaneous. Error rate dropped, Data Rate Control maxed out, Rx Power improved and, best of all, I was locked on only one tower or sector. Here is a side by side comparison of the two antennas before and after:
You can click on the image to enlarge it.
My test setup was a panel/patch antenna I got from HyperlinkTechnologies
It has holes tapped in the back that are the same size as a camera tripod mount so it was a simple matter of mounting a quick-release plate on it and attaching it to the tripod. I have a pan/tilt head so I can make small incremental changes.
Note: If you are confused about the dBi ratings of antennas keep this in mind: The higher the number the narrower and longer the beam, the smaller the number the wider but shorter the beam. For example a 12 dBi antenna will reach further than a 6 dBi but it will have to be aimed much more carefully.
A small dBi antenna can actually be more beneficial if you are relatively close to the tower because you will have less signal loss due to trees, buildings etc. as a result of having a wider RF pattern to capture the signal.