Tilting a Yagi antenna over a tree line?

kaefer · EVDO User Joined: 05 Dec 2005 Posts: 65

In a fringe area when testing a yagi antenna should I keep the yagi parallel to the ground or should tilt up the yagi and point it over the tree line towards the horizon - pointed in the direction of the tower I want to connect to?

In the UHF HDTV forums I see some people getting a better signal when they tilt their yagi's and corner reflectors up a few degrees pointing over treelines.

Thanks for the help,
-Scott

WPSANTENNAS-MATT · Posted: Wed Oct 04, 2006 9:26 am Post subject:

The yagi antenna should be kept parallel to the ground. In the unlikely even the cellular site is at a much higher elevation you may have to tilt the yagi towards the site.

In populated areas there may be 4 or 5 sites that the yagi will pick up so the best way to aim the yagi is to stand next to it with the phone or data card and check the dB level. If the yagi is a 13 dB unit there should be a 13 dB gain when the antenna is correctly aimed at the correct site.

Here is a link to a very detailed instruction sheet

http://www.wpsantennas.com/pdf/installation/YagiInstallation.pdf
_________________
http://www.wpsantennas.com

kaefer · EVDO User Joined: 05 Dec 2005 Posts: 65

Matt,

I've read the Wilson installation instructions and understand the best way of mounting a yagi is above any treeline. In this instance that's not possible. The treeline is simply too tall.

I wonder if focusing the yagi radiation pattern above the treeline helps any (versus aiming the yagi at the trees)?

Am I just way off on this?
-Scott

WPSANTENNAS-MATT · Posted: Wed Oct 04, 2006 10:32 am Post subject:

I would not recommend the lower illustration. The wavelength on the yagi is so tight that you are going to be better off aiming through the trees at a parallel level to the ground.
_________________
http://www.wpsantennas.com

Nolos · EVDO Newbie Joined: 25 Sep 2006 Posts: 10

Wayne Swanson · Posted: Wed Oct 04, 2006 11:23 am Post subject:

n6gn · Posted: Wed Oct 04, 2006 1:29 pm Post subject:

Scott · Posted: Wed Oct 04, 2006 3:25 pm Post subject:

Here's a real-world example for ya.

My new office is at 300 feet above sea level. Either of my Sprint of Verizon EVDO cards get decent signal (-70's). But my speeds suck. 200-300 kbps down on average.

Why? While I have nothing in my path to the towers I am WAY higher (they are at maybe 10ft elevation).

If I point one of my yagis straight out, level, I see a little improvement, just because the antenna has more gain than the EVDO card's antenna. Speeds get up in the average 400-700 kbps down and 60-80 kbps up range. Nothing special.

If I point the antenna DOWN, directly at one of the towers, then I REALLY see some speed.

For Sprint, my signal goes to a -58 or -59 (yes, you read that correctly), and my speeds are now in the 1100 kbps down and 115 kbps up range.

Conclusion: cell site towers have pretty narrow vertical beamwidth. If you are higher or lower, YES, try aiming your yagi appropriately (azimuth angle?).

If you have stuff (trees, mountains, a large stack of buildings) in your way, can you 'curve' your signal around or over them? Probably not, microwaves don't curve so well, but hey, plug your yagi in to your card, watch the numbers and sweep to your heart's content. That's how you learn. :]