FIGURE 7-13. Example of Communications via Fading Spread F Multipath.

TM 11-5820-917-13

far better than use of traditional methods. It can be limited more by factors

such as personnel motivation, communications equipment characteristics, and the

complement of assigned frequencies than any frequency management procedures.

Such procedures must be tailored to each application, however the following guide-

lines have been shown by years of field experience to be effective in a variety

of situations:

a. The Chirpsounder receiver should be placed at the center of communications

control. Up to three paths can be sounded using a single receiver. The (up to)

three Chirpsounder transmitters should be colocated with the communications trans-

mitters at the remote sites, and the diplexer feature considered to reduce antenna

requirements and to factor antenna patterns into the Chirp sounder measurements.

b. If the RSS-4 Spectrum Monitor is used, it should be colocated with the

Chripsounder receiver. If a remote site is over 2000 km away, it is advisable

to place an RSS-4 there, also.

c. If more paths are to be frequency-managed than there are Chirpsounder

systems available, the sounded paths must be chosen carefully. Experience has

shown that propagation conditions from location 1 to locations 2 and 3 are virtually

identical (except occasionally for Es) where 2 and 3 are within 100 km radius of

location 1 provided both paths are over land or over sea water. For paths of longer

length, azimuth and potential propagation differences become major factors. For

example, assume the situation of managing the HF circuits to the six locations sur-

rounding R as shown in figure 7-14 with only 3 Chirpsounder transmitters. Propa-

gation on paths to 1, 2 or 3 should be virtually identical. Circuits to 4 and 5