October 30, 2006

Satellite Audio Doppler sound file from the US Naval Space Command VHF Radar Fence.

Starting in 1958 the US Navy established a vhf radar fence across the US at approximately
33 degrees North Latitude. The system antenna array creates a coast-to-coast fixed fan beam
radiating a high power constant cw signal aimed straight up, with a N/S beamwidth of only
0.02 degrees. The transmitting frequency is 216.980 MHz.

The purpose of the system is to detect any satellites or objects crossing the "fence" based on
the doppler produced by the satellite’s motion. Typical satellite’s orbits will cross the fence
around 4-5 times per day. The system makes on average, one satellite detection every ten
seconds. A typical satellite will be illuminated for about 0.5 second per pass.The range of the
radar is about 10,000 nautical miles.

Originally this system was named the NAVSPASUR Fence. Now it is called the NSSS Radar
Fence. There are three transmitting locations with the central and highest power one located near
Lake Kickapoo, Texas, and six receiver sites from Georgia to Southern California. Total
transmitter power is 767 KW and with the 40 dBi antenna system gain, the ERP is +98 dBW,
or 6.3 billion watts! This is CW output, 24 hours a day!

You can look up several fascinating web sites about this system by going to a search engine and

Recently, Kerry Banke, N6IZW, set up a 7 element 220 MHz yagi receiving antenna and 0.4 dB
NF LNA/direct conversion receiver at his home in La Mesa, California. He then recorded
several hours of reception of the 216.980 MHz doppler returns . He edited the audio into a three
minute MP3 file containing a variety of doppler crossing sounds. Click Here if you would like to listen
to this file. We do not know what produced each doppler return in this file, but they are interesting
to listen to.

If you have any questions about this, you can email Kerry at kbanke@sbcglobal.net