48. ABM Frequency Assignment Plan (Six Block).
The ABM plan is used for a complex network where there are more
than two transmitters and two receivers at the same location (figure
21).
Figure 21.
Complex systems.
a. Advantages.
The ABM plan divides a broad frequency region
(all or a large part of a band allocated) into six frequency blocks
of suitable widths.
Frequencies obtained are divided approximately
equally among the blocks. The basic planning is then done in terms
of these blocks. This results in the following advantages:
(1) Any station can be connected with nearly any other station
with minimum effect on the rest of the network.
(2) Planning is simplified.
(3) Quick changes of frequencies can be accomplished without
any trouble.
(4) By dividing all frequencies into six blocks, it makes all
allocated frequencies useable.
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