Comments on the performance of selected low-power HF radio sets in the tropics

The performance of five low-power HF radio sets was measured at 3.6 MHz under field conditions in Thailand. Variations in performance were noted for CW and voice transmissions as a function of type of set, type of antenna, time of day, and communication range (5-100 mi) in tropical forest (jungle), mountain, and delta terrain. Radio teletype (RTTY) tests over longer paths (out to 1320 km) were made using a jeep-mounted set. The results showed that relatively good communications can be achieved in the tropics on short and intermediate length paths with low-power sets--especially when the proper antenna is used and when the operating frequency is properly chosen.