Determine Line of Sight

4 May
Determine line of sight between two points

Determine line of sight between two points

EDIT: This post is old. the link to the software doesn’t work anymore, but Google has some ideas. Download at your own risk.

I use EVDO to connect to the intertubes. My indoor 7dbi omni antenna topped out at 1mbps down / 100kbps up on a very good day, usually lingering at about 500kbps down and 60kbps up. I bought a three watt amplifier package (came with a 5dbi omni) and gave it a shot. It increased my signal a little, but it also increased the noise. My speeds actually dropped a little.

I called Alltel to find out where my tower is located. It’s almost exactly 3 miles away… through hilly terrain. I’m located in what’s known as a “holler” in these parts. A hollow is essentially a valley in a valley, a nightmare of sorts in the RF arena.

I wanted to get a yagi antenna to point directly at the tower, but I wanted to find out if I had line of sight (LOS). It would be a waste of time and money to use a yagi or grid antenna without LOS.

I found a great, free program called RadioWORKS from Desert Hail. Enter the lat/lon of both points and it displays a graph to help you determine if you have line of sight between two points. It allows you to easily enter antenna elevation at both locations, so you can play around with the figures to determine how high you need to mount to obtain line of sight.

So, from the LOS survey I posted above, I determined that though I have LOS, part of the Fresnel zone is occluded. Rather than jump right to a yagi/grin directional antenna, I’ve decided to take my omni antenna to the roof to see if that helps. It might give me enough. I hope so… Though I found online sources to calculate bearing between two points, aiming a directional antenna is a task I’d like to avoid.

EVDO Antenna Line of Sight Update

I took the works to the roof and achieved a much faster connection. However, dealing with the inevitable lightning strikes is a daunting task. The antenna sits on a solid steel slab and is otherwise very inviting to lightning. Properly grounding the antenna involves an additional connection which loses precious dbi. And the mounting logistics are annoying too. On a whim, I moved the antenna to a second story window with decent LOS to the tower. Problem solved. It’s not quite as fast as it was on the roof, but it’s better and good enough. Lesson learned: If you’re able to place your antenna higher in your house, give it a try. I moved my Cradlepoint MBR1000 upstairs and ran some cat5 to a little switch that sits where the Cradlepoint mobile broadband aggregator used to be. As an added benefit, my wifi signal is also better when broadcasting from this height.

Line of sight update two

Checked today and the link to the line of sight software is dead. In case it doesn’t come back up or dies again in the future, please Google for radioworks line of sight to find other download sources for this great free software. (Update 3 – vendor link is working again. I had to remove the www. from the url. I’ve informed them of their webserver misconfig. Awful canonical SEO problem. They helped me with LOS, I’ll help them with SEO!)

Dan Dreifort consults on SEO and usability. He helped start an ISP in 1996. That ISP is still up and running, somehow. When he first started looking into determining line of sight he couldn’t believe the lack of available tools and information. Then he realized he was spelling it wrong. Line of site. Yeah, that doesn’t work as well.

3 Responses to “Determine Line of Sight”

  1. anupam January 17, 2011 at 1:35 pm #

    very good software

  2. sez April 20, 2013 at 10:53 pm #

    your link above to radioworks is https:// so it doesnt work, revert to http:// and its all good!

    • dandreifort April 20, 2013 at 11:03 pm #

      Thanks for the heads up. Fixed! Not sure why they keep changing the config on their webserver. I reached out to them last time, but I won’t bug them this time. Nor will I add “update 4!” to the post. …But let this be a lesson to anybody with a website; leave things well enough alone. Don’t go changin’, rearrangin’. Google (and all of your backlinks) liked you just the way you were.

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