Answer to Question #3392 Submitted to "Ask the Experts"

Category: Micro/Radio Waves, Radar & Powerlines — Satellite Dishes

The following question was answered by an expert in the appropriate field:

The house that we just rented is next door to what seems to be a communication center, with five to six satellite dishes right next to one another. Each satellite dish is about 10 feet wide. I have read on your Web site that the dishes do not pose any health threats since they do not emit ionizing radiation. However, the microwave antenna for the dishes does emit microwaves. What does the microwave antenna look like? Could you send me a picture of it? How far away from the antenna is considered a safe distance?

Let me start with a picture as you requested. Check out the Richard Tell Associates, Inc. Web site to find some photos of satellite dish facilities.

The large (about 10 feet across) round dishes in the photos receive radiofrequency (RF) signals from satellites and, of course, the process of receiving signals does not transmit any radiation at all. Some facilities also use large dishes to send RF signals to satellites. These dishes may transmit fairly powerful RF signals but only in a very well-collimated beam like a flashlight. The beam is aimed at the satellite. RF signal strengths can be large directly in front of a transmitting satellite dish, that is, within the beam. But there is very little RF signal, and no hazard to people, outside the beam being transmited from a satellite dish.

The small (two to three feet across) round dishes mounted on the tower (in the black and white photo) are microwave dishes. These dishes are used to send and receive signals to other microwave dishes located on other towers within typically a few miles distance. Because the distance is short (compared to transmitting all the way to an orbiting satellite) the microwave dishes operate at relatively low power. Like the satellite dishes, the transmitted RF signals from a microwave dish are sent in a narrow flashlight-like beam. So again, unless you are directly out in front of a microwave dish in the transmitted beam, there is no hazard to you in the nearby area.

Gary Zeman, CHP, ScD

Answer posted on 20 February 2004. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.