User manual
Using the RDS SECTION (FM version ONLY)
ENG
Page 74
29.9 AF METHODS A AND B
There are two ways to transmit lists of alternative frequencies: Method A and Method B.
In both cases the lists should include only those frequencies for the nearest transmitters and repeaters (with overlapping
coverage areas).
Generally speaking, Method A is used when the list contains no more than 25 frequencies, and Method B when the list is
longer (for a maximum of 24 lists).
Method B is recommended when splitting areas or when different programs are broadcast.
NOTE: use of encoding method A or B is not explicitly assigned by a dedicated signal to the receiver, as the latter is
capable of identifying which method is used by analyzing the transmitted data structure (whether or not they are
organized in pairs).
METHOD A
Compile the AF1 list assigning the tuning frequency (i.e. the frequency carrying the list of alternative frequencies) in the
first position, and then continue in strictly increasing order with the alternative frequencies transmitting exactly the same
program.
We recommend recording the alternative frequencies (those of adjacent transmitters and repeaters with overlapping
coverage areas) on each transmitter, being careful that the first position indicates the frequency carrying the list of
alternative frequencies.
For example, in the situation shown in the figure three transmitters (B, D, E) intersect only in two coverage areas:
between B and D, and between D and E. The following lists should be loaded in each transmitter:
AF1 AF2
f Tx B f Tx D
Tx B lists
(tuning frequency: f Tx B)
f Tx D f Tx B
Note that the frequency of transmitter C is not included
in the list, since the latter’s coverage area does not
overlap with that of transmitter A
AF1 AF2 AF3
f Tx D f Tx B f Tx E
f Tx B f Tx D f Tx D
Tx D lists
(tuning frequency: f Tx D)
f Tx E
Coverage area D partially overlaps that of both
transmitters B and E, and thus it is recommended to
load the lists for both adjacent transmitters. Be careful
to list all frequencies above the tuning frequency in
ascending order.
AF1 AF2
f Tx E f Tx D
Tx E lists
(tuning frequency: f Tx E)
f Tx D f Tx E
Note that the frequency of transmitter B has not been
included in the list, since its coverage area does not
overlap with that of transmitter E.
METHOD B