User's Manual

Heli-Coder 4 Transmitter Operation Manual | Doc. No. 6051452100 Rev. B1
Broadcast Microwave Services, Inc. 31
The guard interval determines the maximum echoes length dispersion that the system can tolerate. From this figure, we can estimate the maximum
transmission range that the system might offer for a typical terrestrial channel (with adequate RF power).
The following table summarizes the results of the 4 possible guard interval values:
Guard Interval
Ratio
Guard Interval
Duration (us)
Maximum echoes
dispersion (km)
Maximum transmission
distance (km)
1/32 7 2.1 2-6
1/16 14 4.2 4-12
1/8 28 8.4 8-24
1/4 56 16.8 16-48
Transmission distances can be increased when using directional antennas, but signal break-ups can still
occur if long echoes enter the receiving antenna beam width.
END