Yagi antenna experience.

jfulmer · EVDO Heavy User Joined: 30 Jun 2007 Posts: 113

I recently started using Sprints EVDO service. being on the fringe of their supported area, I got a S720 card (with a PCMCIA/PCI card to put in a server) and a Wilson Trucker omni-directional antenna to see if I had decent enough reception to make it viable.

With that setup, and mounting the antenna on a 15ft pole, I got a EVDO RevA ~-82db signal (according to Sprint's connection manager), and ~600kbs download/100kbs upload maximum with. While this was acceptable, since I am in the boondocks and have very few other options, I wanted to see if a directional antenna would improve things.

Keep in mind my situation There is only one Sprint tower in my area, and it's location is very well defined, and it is 7 miles away with a sizable number of trees and hills between me and it. If there were more towers around, it might make more sense to stay with an omni-directional antenna, but as it is, a directional antenna can only help my particular setup.

I purchased a Wilson 15dbi 1900Mhz Yagi antenna. http://www.wilsonelectronics.com/ViewProductB.php?ID=15 This runs about $55, and looks like it's been laser cut out of a sheet of 1/8in aluminum. To be honest, it feels a little flimsy, and mounts directly to a pole. It uses an N-Type female connector to the antenna cable. I also purchased a 15 foot LMR-400 N-Type Male<>Male antenna lead cable from eBay, and a N-Female->FME-Female adapter to connect to the cable leading to the EVDO card.

This last weekend, I drilled a large hole through the side of the house (n-type connectors are BIG), and mounted the antenna in the place of the omni-directional. I did a rough aim (turns out my 'rough' aim was as good as it gets... I later had another person check signal levels while I turned the antenna pole, and I ended up in the exact same position as where I started), and went to check.

My signal leve increased to about -75db, a 6db (4x signal power) gain over my normal with the omni directional. This fits exactly with what I should have expected, 10db omni vs 15db directional, plus a slight gain due to the much better properties of the LMR-400 cable.

On speed tests, I now get up to 1.2mb/s vs 600kb/s download. Upload is still under 100kb/s, but I can live with that. Latency (ping times) does not appear to have changed significantly. I also note that in peak usage times, my speeds dip to 200-300kb/s, which means that Sprint has limited bandwidth on this particular tower... Sad

So I can definitely say that if you are on the fringes of EVDO coverage, and get modest speeds, AND you are willing to be locked to one tower, a Yagi antenna certainly can help.

All told, I spent about $95 on the directional antenna, cables, and adapters. I still need to invest in a lightning arrestor for the antenna cable and I may put the antenna up another 4 feet. I also need to brace the antenna cable inside the house, so that if the antenna mast does fall (unlikely), it doesn't rip the connected computer system through the wall.

dan1101 · EVDO User Joined: 17 May 2007 Posts: 41

I'm in the same situation (about 6 miles from tower, hills and woods in between.) I recently got the Yagi, and using with the Wilson amp it increased my signal to about 90db, and I get about an 800k down/ 150k up connection. Decent but not great. I need to try and get mine higher though.