PANAMA VHF AND HF JUNGLE PROPAGATION.
JUNGLE COMMUNICATIONS EQUIPMENT TEAM CANAL ZONE
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In hilly, mountainous, forested country, VHF communications are much better than expected. These tests show that it is reasonable to expect complete reliable coverage of an area 25 miles in diameter by using a balloon antenna 200 to 400 feet high at the command post with the patrol antenna raised on a 100-foot lightweight, blow-up mast. The steep, sharp, high, tropical hills are an advantage in most cases to VHF propagation. A better way to package the 6-ounce, lightweight cable such as is used for a 100-foot measuring tape is required. The PRC-25 is too heavy if it has to be carried 25 miles on jungle trails. A lightweight set similar to the PRC-35, but less the four-channel mechanism would be more useful if the 25 mile distance is actually a firm requirement. For HF, low power, less than 100 watts using vertical-incidence for the E layer reflection in the daytime is dependable. The use of shortened, quick-erectable, horizontal, antennas is feasible. Interference is the only reason that communications are difficult. The low frequency end of HF sets should start at 2 Mcs or lower, not 3 Mcs, and above 8 Mc is not useful for 25-mile circuits. The center-fed matching system is the most useful because it can be used for both short antennas and half-wave antennas with the least matching and tuning trouble. At night, from 2000 hours to 0600 hours in the morning, the frequency must be below 2.5 Mcs and a half-wave, efficient antenna must be used. The GRC-9 is too heavy for foot patrols.
- Radiofrequency Wave Propagation
- Radio Communications