Figure 2-15. (Eb/No) as a function of signal/noise meter reading.

TM 11-5820-803-12

2-11. Special Applications

(2) The bit-error rate performance with

external coding depends upon the type of external

a. The PSK modem input and output digital user

coder/decoder used.

interfaces are compatible with each other. The interface

signals normally connected to a digital user may be

(3) The PSK modem may be used in

connected directly to another PSK modem to implement

conjunction with other than rate one-half coder/decoders;

a ground relay configuration, as shown in figure 2-17. If

e.g, a rate three-fourths coder/decoder. In this case,

the two earth terminals are widely separated, the PSK

however:

modem may also be interfaced with another PSK

(a) The coder section must be capable

modem over a shielded cable or a line-of-sight (LOS)

of operating with only one clock input at the input data

microwave link.

For detailed information on cable

rate, and must produce an output clock at the output

interface, refer to paragraph 2-9 b. All coding options

symbol rate.

may also be used in a relay configuration.

(b) The decoder section must be

b. In the external coding mode, the PSK modem is

capable of operating with only one clock input at the

intended for normal operation with an external rate one-

symbol rate, and must produce an output clock at the

half Viterbi coder/decoder (KY-801/GSC). However, the

output data rate.

modem may be used in conjunction with other types of

PSK

modem

operating

coders/decoders, within the following constraints:

procedures must be revised to reflect the appropriate

(1) The interface levels (line drivers and

data rate to symbol rate relationship.

receivers) must be compatible (see paragraph 2-6 for

further information on interface levels).

2-16