JRC JSS-2250 Instruction Manual page 215

Selecting communication frequencies in the MF/HF band (reference)
When communicating with the MF/HF radio equipment, select frequencies referring to the
frequency transition table and the radio wave propagation images (excluding the polar
latitudes) shown below
Example: When communicating with a station approximately 5000 km away at
around 12 pm in the winter with a sunspot number of 100, select
frequencies in the 18, 22, or 25 MHz bands for the best results.
Frequency transition table
Transmissions conditions 通信条件
距離 季節と時刻
Distance Season & time
冬
Winter
遠距離
Long distances
(e.g. 5000 km)
（例：5000km）
Summer 夏
Winter
冬
Short distances
近距離
（例：1000km） (e.g. 1000 km)
Summer
夏
Radio wave propagation images
9
These are based on the prediction of HF radio wave propagations. Communication is not
guaranteed.
9
.
Guideline for selecting frequency (for a sunspot count of 100)
周波数選択の目安
2M 4M
日中 Day
夜間 Night
日中 Day
Night
夜間
Day
日中
Night
夜間
Day
日中
Night
夜間
（太陽の黒点数 = 100の場合）
6M 8M 12M 16M
Appendix
18M 22M 25M
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