Best of the ISP-Lists

Fixed Wireless Equipment

Antenna Advice for a New WISP

As members of the ISP-Wireless list discuss the relative benefits of various antennas, we provide additional information from the ISP-Planet archives.

[March 27, 2007]

On the ISP-Wireless list in March, KS asked:

List,

We are looking at installing a Trango customer that is 14 miles away from the tower. Obviously, we'll need an external dish to go the distance. Pacwireless has both grid and solid dishes in the gain that we need, and the grid are substantially lower price. Why not always use the grid? What's the difference?

Some said that the weather will determine your choice.

[RS suggested] "If ice is a concern, get a dish; if not, don't."

[JS explained] "Wind load is less on grids. That can be a design concern depending on tower, mast or mount installation plus wind and ice issues. Solid dishes are usually better performing in noisy area because of improved Front to Back ratios (F/B Ratios) and beamwidth pattern. For point to point installs, the tighter the better. That said, some grids have good RF characteristics. Homework time. . . "

[GR added] "The dish is more solid. I've tried both and like the dish better."

Ice has always been an issue for wireless, as shown in this article from 2000, The Ice Storm. Wind issues are also common, although they are usually not as spectacular as the events described in this article from 2004, The Guys You Depend On.

JB said that ambient noise would also affect the decision.

For an isolated subscriber, grids are fine. Putting a grid on a tower is in invitation for RF trouble. Even if you're the only one for miles, someone is bound to come along and use your frequency on a different path, and you'll pick up interference on a sidelobe.

Ed. note: For more detail and some nifty pictures of antenna radiation patterns, see Marlon Schafer's article from 2001: How to Pick the Perfect Antenna.

For definitions of key terms, see Jack Unger's glossary and Michael Young's article dMystifying the dB. Jack Unger's Ask-Wi is the only independent outfit we know of offering wireless broadband classes (he calls them workshops becuase they are intensive sessions lasting a day or two).

While many startup WISPs put a great deal of thought into choosing the right antenna, some fail to consider the importance of batteries.

As JS said, above, if you're starting out, you've got plenty to learn, but the beauty of the internet is that you can learn much of it online. Keep in mind, however, that we cannot teach you about the law.

—End