Specifications

3-46 888-2857-001 5/9/13

WARNING: Disconnect primary power prior to servicing.

Section 3 Operation

Platinum VAX-C Series

Figure 3-28 CTTB Setup Screen 2

Table 3-23 Xmtr Home>Exciter Home>Setup>CTTB Modulation>Next (screen

Fields Explanation

Output Bandwidth Choices are 8 MHz, 7 MHz, 6 MHz or 5MHz.

Carriers Choices are Multi, Single, or Two Pilot.

Multi = COFDM type modulation, Single = single carrier modulation

system, Two Pilot = single carrier modulation mode with two pilots.

Guard Interval Choices are PN945 (1/4), PN595 (slightly less than 1/6), or PN420 (1/9).

This is the length of the guard interval in symbols. The total frame length

is 3780 symbols. Guard interval is the guard interval symbol length

divided by the total symbol length. Example: 945/3780 = 1/4.

The Guard Interval is the time, between symbol transmissions, when

nothing is transmitted. The guard interval is entered as a fraction, which

represents the guard interval time as a fraction of the useful symbol

duration. Total symbol duration is the sum of the useful symbol duration

plus the guard interval. In the 2k mode, useful symbol duration is 224

microseconds and in the 8k mode, useful symbol duration is 896

microseconds.

Guard Interval PN Choices are variable or constant. Constant only used with PN595,

Variable is used with PN945 and PN420.

Constellation Choices are 4QAM, 16QAM, 32QAM, or 64QAM. Constellation refers to

the size of each RF sub-carrier constellation. LDPC Rate: Choices are 0.4

(2/5), 0.6, (3/5) or 0.8 (4/5). The LDPC Rate provides three rates of

forward error correction. The decimal, or fraction, gives the relative

efficiency of the forward error correction by dividing the information bits

by the total block length. For example, block length = 7488 bits,

information bits = 3008, therefore: 3008/7488 = 0.4 or 2/5. This indicates

that there are two information bits for every five output bits.

Time Interleaver Choices are 240 symbols or 720 symbols. This is a data convolutional

interleaver. The data is interleaved to a depth of 240 or 720 symbols.