(3) The planner must consider the type of propagation to use (ground wave or sky wave) to
achieve the best communications. When sky wave propagation is used, planners must review a
frequency chart. That chart lists the optimum frequencies and the associated time of day for achieving
the best sky wave effect. As atmospheric conditions change during the day, some frequencies are better
than others for long-distance propagation.
(4) Antenna design can be difficult for operators who do not know the relationship between
wavelength and antenna length. They must be trained in erecting their antennas. They should have all
accessories for their AN/GRA-50 doublet antennas, including tape measure, insulators, antenna wire,
and cables. The NVIS antenna can be used to extend IHFR range up to 300 miles by using sky wave
propagation. Planners must ensure the antenna is set up where maximum propagation will occur. They
avoid setting up under a thick jungle canopy or near large objects (bridges, buildings, and so forth) that
can absorb and attenuate the signal.
(5) Planners must consider remote operations. Only the AN/GRC-193 IHFR can be remoted.
A unit must have needed remoting items on hand before it departs on a mission.
(6) Planners need to consider secure mode operations. The KY-65 (voice transmissions) and
the KG-84 (data encryption) are the only COMSEC devices available for secure mode operations.
Planners must coordinate with all users to ensure they have the correct keying variables for specified
periods.
(7) Interoperability with older systems needs to be considered. IHFR can interface with
older AM radios, such as the AN/GRA-106. Planners should have face-to-face coordination with users
to discuss the procedures for communicating between newer and older radios. The procedures are
outlined in FM 24-18, Tactical Single-Channel Radio Communications Techniques.
(8) IHFR is a modular design system. In the field, maintenance can be rapidly done by
replacing subcomponents that are linked together with quick-release clamps and cable connectors.
Planners must ensure that reasonable preparations are made to provide the needed maintenance support.
(9) Planning training is a required factor. Training should be progressive, from basic to
complex. Exercises should be progressive to add increasingly realistic challenges. Realistic degradation
to various systems should be programmed (jamming, lethal destruction to equipment, people, and so
forth). Interoperability training with supporting reserve and allied units should be conducted.
c. IHFR is a highly reliable communications system. However, to effectively use IHFR, signal
planners must review every aspect of signal operations. Users must be highly proficient, especially if
they are operating at a distant remote site where mobile maintenance teams do not usually go.
Successful IHFR operations reflect good training.
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