Why do C and Ku Bands on the Same Satellite Have Different Letter - Number Codes?

Many satellites are hybrids, meaning they have both C and Ku band transponders. In the main Satellite menu, these C and Ku bands will have different two-character codes. For instance, Telstar 4 is a hybrid. Its C-band code is T4, but its normal Ku-band code is W4.

Why? The Chaparral receiver thinks that each band (C and Ku) on each satellite is a separate satellite with its own unique two-letter code. When you switch from T4 to W4, it engages a whole different set of electronics. This is like switching a radio from AM to FM; your dial may be in the same position, but you're listening to a different part of the radio spectrum.

In our example, since T4 is used for the Telstar 4's C-band transponders, the receiver cannot use T4 again for any satellite in memory, including the Ku-band of that same satellite. An operator adding any new satellite must choose a letter and number which are not currently in use. Think about this: the Telstar series has five active satellites (all starting in "T"), and there are only 10 numerals available, so if the operator is determined to give the Ku-side of T4 a T-prefix, the only available combinations are T6, T7, T8, T9 or T0 (T-zero). (For more about the codes, see What are the Correct Two-Letter Abbreviations for Satellites? )

To carry the example further, we've noted that Chaparral currently uses W4 to designate the Ku-side of T4. However, the "W" prefix is also used for the C-band side of GE satellites, and GE-satellites 1, 2 and 3 currently exist. If another GE-satellite goes up, since W4 is already in use Chaparral will have to find another prefix for the GE-series or will have to assign a new code to Telstar 4-Ku. Clearly, this situation can be confusing! It seems that since most consumers use the C-band satellites, Chaparral uses the most "intuitive" letters for C-band and less intuitive letters for Ku satellites, which are used more by industry.

• Question: If the two-character code doesn't tell me, how can I tell which satellite I'm watching?
• Answer:You can get a copy of a satellite chart (found in "Orbit" and similar magazines) and check the satellites on each side of the one you're watching. By referencing the channels on those satellites to the chart, you can determine which satellite is in between the ones on either side.

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Copyright 1997, Dr. Albert E. Powell, Jr.
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