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DIGISONDE-4D
SYSTEM MANUAL
VERSION 1.2.11
SECTION 5 - SYSTEM SOFTWARE – ANNEX C 5-75
5:155. Each Frequency Group contains a 6-byte PRELUDE and a single height profile of a variable length.
Table 5C-39 summarizes the possible settings of Frequency Group lengths depending on the number of heights
selected by the operator.
Table 5C-39: Length of the RSF Frequency Groups Depending on Ionogram Settings
NUMBER OF HEIGHTS
PREFACE Char #36-37)
NUMBER OF
FREQUENCY
GROUPS IN A
BLOCK
NUMBER OF RANGE
BINS STORED IN A
GROUP
LENGTH OF A FREQUENCY GROUP
(BYTES)
5:156. For each sounding frequency, one or two Frequency Groups are stored depending on a setting of O/X
polarization option, A, PREFACE Char #29. If A is less than 8, both polarizations are stored each taking an
individual Frequency Group, otherwise only O polarization height profile is stored for each frequency.
Each range bin takes 2 bytes in an RSF Frequency Group (see Table 5C-40 and Table 5C-41)
Table 5C-40: Content of an Individual Range Bin in RSF File Format
Table 5C-41: Individual Bit Sections of the Range Bin
5:157. The 6-byte PRELUDE precedes each set of range bins in a Frequency Group (see Table 5C- 42). The
PRELUDE uses a packed-BCD encoding scheme where each byte contains two 4-bit digits (0-9) each taking a
nibble. The frequency reading stored in PRELUDE is the actual sounding frequency. The offset from the nom-
inal frequency is stored in byte #4. If offset was caused by forcing of sounding out of restricted frequency
range, the actual frequency reading is given and the offset is set to E (hex) to indicate the case.
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