| 释义 |
high-frequency communications high-frequency (HF) communicationsThe communications carried out at frequencies between 3 and 30 MHz. HF waves are dependent mostly on reflected sky waves and are affected by ionospheric conditions. HF is used for long-range communications. The lower frequencies in this range are more suitable at night, and the higher frequencies are more suitable for day operation. Expected ranges may vary up to 15,000 NM or more. |