My radio antenna location is great for HF communication with Europe, and now I know why.

Most hams use a half-wave dipole or beam antenna for high frequency communications. These horizontally polarized antennas are usually hung high in trees or on top of a tower. When the radio signal leaves the antenna, part of the signal moves directly up into the sky. Another part of the signal heads downwards and gets reflected off the ground. These direct and reflected rays then travel thousands of miles and are bounced off the ionosphere to (hopefully) distant lands.

The effectiveness of these antennas depends on both their height above ground, and the nature of the terrain near the antenna. Each high frequency band has a sweet spot for antenna height. This is why most hams try to get horizontally polarized antennas at least 50’ above ground, often with a tower.

But the nature of the terrain surrounding the antenna also has a big effect on antenna effectiveness. Ideally, you want to be on a hill and never in a valley.

Tucked inside the CD-ROM distributed with the ARRL Antenna Book is a software application called High Frequency Terrain Assessment, or HFTA. This program lets you explore the effect of terrain at your location on the performance of your antenna. A U.S. ham, K6TU, has automated the process of providing terrain data for your location. All you need to do is register at his web site, and provide your exact latitude and longitude.

My Radio Antenna Location

The above picture shows my radio antenna location using Google Earth, as well as an example of terrain assessment to north, east, south and west in the upper right. The location is at the southern edge of a park that runs through Calgary. The antenna is a two-element beam on a fifty foot tower.

• To the north (blue line) I am on a steep hill that plunges down around 100’ over the first quarter mile, before rising back up on the other side of the park.
• To the east (red line) the terrain declines fairly steeply by 150’ and remains there for several miles. In effect, I am on a hill.
• To the south (green line) I am effectively in a valley.
• To the west (aqua line) my location is quite mixed – a nearby hill, followed by a valley, then followed by gently rising terrain, which is not surprising given that I live in the foothills of the Rocky Mountains to the west.

I will explore the effect of terrain at my radio antenna location in future articles. But for now, as you may have guessed, my best high frequency performance is towards Europe, Middle East and Africa (blue and red lines) where my hillside location provides the best combination of direct and reflected signals.