WSR-ANT
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often be recorded with very little noise. This allows a full, high
quality pass, nearly horizon-to-horizon to be recorded with the
NOAA satellites, a picture 2940 miles long by about 1875 miles
wide, it comes to over 5.5 million square miles with a resolution of
2 to 3 miles (in the center of the pass). For a receiver in Florida
that means a picture from the northern part of South America to
Hudson Bay! In addition, because of the narrow beam width,
extraneous noise sources often do not interfere with the satellite
signal.
The disadvantages of a controllable Yagi are complexity, higher
maintenance, and cost. Many users find that the stationary
turnstile antenna is very adequate for their needs.
Another practical type of antenna is the volute VHF antenna. It
looks like a twisted set of wire, but it is quite effective for receiving
satellites, since it doesn’t have as many nulls and peaks due to
polarization of RF signals. These are tough to assemble out of
household equipment and it is very difficult to bend the wires
‘perfectly’, but are widely available through weather satellite
companies.
TV transmissions and GEO synchronous satellites transmit in the
microwave region, making a dish an effective solution for clear
reception. Dishes are very directional, and have plenty of gain at
these frequencies. The satellites that this antenna is designed for
operate in the VHF band, making the size of the required dish
impossibly large for good gain and directionality.
Since we didn't want you to have to go through the expense of an
automated antenna system that can rotate on two axes, or the
trouble of tracking a satellite manually, we came up with a simple
solution. The antenna we have chosen is called a turnstile
antenna, and has the characteristics that we require. This antenna
is directional in the upward direction to receive signals in the sky.
The antenna is circularly polarized as well, just like the weather
satellites, and makes for better reception.
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