(3) If you consider transmitter frequencies only, the triangle
requires only six blocks of frequencies.
In figure 2-15, these
blocks are labeled from I to VI. Relative to location A, you can see
that frequencies I and II are transmit frequencies, and that IV and V
are receive frequencies.
(4) You must analyze the situation in order to set up a system
between sites A and M. The transmitter frequency from A must be from
block I and the receiver frequency from block IV (see figure 2-15).
Each system has a block from which you can take the appropriate
frequencies. Use the same method to set up a system between sites B
and M. In the example in figure 2-15, paths III and VI apply.
(5) Frequency separation required between the transmitter and
the receiver applies to blocks of frequencies. Frequency separation
requirements differ for each type of radio system.
Refer to the
appropriate TM for your system.
(6) The triangular situation of 2-15 requires six blocks of
frequencies.
You also must consider the necessary frequency
separations.
This requires you to determine the number of
frequencies required in each block. To do this, you must analyze the
system requirements, such as shown in figure 2-16.
As you can see in figure 2-16, the system illustrated shows three
paths from site A to site M (numbered with arrows). Therefore, block
I requires a minimum of three frequencies for A to M shots.
Continuing this analysis yields the requirements shown in figure
2-17.
(7) Divide your allocated frequencies into six blocks.
You
must include at least as many frequencies for each block as required
by your analysis in the preceding step.
Figure 2-18 illustrates an
example of such an allocation.
There are no definite procedures for this division other than trial
and error. You must check the separation between the blocks. Again,
the required separation depends on your equipment. Figure 2-19 shows
the system with frequencies assigned.
c. Double ABM Plan. If your traffic load is particularly heavy,
you may require an additional radio link. If this is the case, you
need additional equipment and additional frequencies.
This also
requires additional frequency planning. The double ABM plan works in
this type of situation.
2-26
SS0016
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