Originally Posted by chuyler1
Seriously? Have you proven this yourself or is this just internet hype? If it's true that's pretty cool...but how often do you have a line of sight to the nearest starbucks from your campsite?
...Walmart parking lots excluded
I am an electrical
engineer with a focus on antenna design, and Ham radio operator who experiments with antennas. Here is what I found out about WiFi antennas.
First the basics: There are two types. Omni Directional and Beam antennas.
Omni antennas perform equally good in all directions. High gain antennas are created by stacking antenna elements vertically which takes the typical donut shaped antenna pattern and flattens it so more of the signal and sensitivity is sent horizontal for greater distances. There is no point in radiating energy going up into the air. Think large thin pancake pattern compared to fat donut for high gain antennas. All the energy is sent along the ground where it is wanted.
While you may want a donut on a sailboat heeling over, for most applications high gain antennas work better than lower gain antennas and require no pointing. I have two of these in a 9db and 11 dB gain versions. Each 3dB gain doubles the signal strength. So 9 dB has eight times more signal strength on transmit and receive. A 12 dB antenna has a 16 times stronger signal.
Beam type antennas, many of which are Yagi-Uda type named after two inventors who developed this antenna type independently, work differently. In this case the elements are mounted at 1/2 wave length spacing on a horizontal bar. The element sizes are also close to 1/2 wavelength where the lengths are slightly smaller and increase from front to back. Imagine all the radiated energy from a simple donut pattern is now pulled and stretched in one direction. These antennas must be pointed at the WiFi source you wish to hook up to. Often these antennas have similar gain values to the omni-directional antennas.
This is the model beam I have:
Cushcraft PC2415NA 2.4 GHz Articulating Directional Yagi Antenna
OK so which is better?
If there is only one WiFi node in your area, then the Omni works easiest as there is no pointing involved. You might find, moving your trailer one or two feet improves your connection to the gateway WiFi, but it is basically plug and play.
However, if you are parked in the street of a residential community with dozens of WiFi emitters and only one is free, an Omni antenna will be picking up all of them and chances are very high that there will be other emitters operating on the same channel as your gateway WiFi. This causes interference and makes it difficult if not impossible to connect unless you are right next to the gateway access point.
Here is where a directional antenna works wonderfully. When pointed towards your gateway access point, it is extremely sensitive in that direction only and other interfering Wifi emitters are received weakly. These beam type antennas allow you to make a connection over a much longer distance in the presence of competing signals. There is a disadvantage. High gain beam type antennas have narrower antenna beams patterns and are harder to point accurately. The higher the gain the harder they are to point accurately but they do work over longer distances. I think 12 dB gain is just right for most purposes.
How long a distance can you make a connection? Using extremely high gain antennas mounted on dishes to further block unwanted signals and increase gain, the record is over 25 miles with an amplified link on both ends and two people working hard to make it happen.
It is quite possible to reach a mile with a beam type antenna but more practically you should be able to reliably achieve distances over 1/4 mile or more with a sensitive, say 12dB gain antenna and a 1 watt amplifier.
Attaching the amplifier to the base of the antenna directly or through a short feedline improves performance, as signal losses in the feedline are very high at these frequencies. Even without an amplifier a directional or beam antenna will give you a stronger, more reliable signal. My amplifier is located 6" from my antenna.
If I were running a campground I'd use an amplified high gain Omni antenna. Or perhaps more than one access points on different channels and locations if I wanted to be known for having great WiFi.
If I were a customer staying at a campground I would use a directional antenna on a mast that I could rotate by hand and lock into position. I would also use a 1 watt amplifier and choose a campsite with line of sight vision to the campsite WiFi access point. Many times the WiFi only works in certain locations. If you don't want to have to move to the WiFi a beam antenna brings it to you.
If I were traveling in a parking lot trying to connect to a free WiFi but not wanting to go into a store to use its hotspot, I would either have my beam antenna in a fixed mount and steer it by turning my vehicle or else park where I wanted and steer the antenna at the hotspot. This works well at night when places are closed but access points are still running. I can keep a low profile and take advantage of the sites full bandwidth as I am the only user.
A few final thoughts:
if you don't have line of sight you can sometimes bounce a signal off another RV or a building. So the best signal may not come from pointing your antenna directly at the emitter. Most software will show the signal strength and allow you to steer your antenna for maximum signal.
Directional antennas also have nulls where they don't receive anything on the back side. If there is an interfering signal, twisting your antenna to 'null' them out will allow you to pull in a weak WiFi emitter that is farther away. While you might not have maximum signal strength pointed at your access point, eliminating the other interfering signal provides a reliable connection.
Finally, I have a free wifi service that comes with my broadband cable service. Mostly this consists of access points along the coast of Connecticut. Using a high gain antenna will not work unless I provide the MAC address of the device I am connecting with, to the cable company. If you chose to use a paid wifi service, along with a complicated antenna and amplifier, be sure to test out your configuration prior to traveling as you may find the set up and configuration to be more difficult than it should be.