Jiyuan

Jiyuan (simplified Chinese: 济源; traditional Chinese: 濟源; pinyin: Jǐyuán) is a sub-prefecture-level city in northwestern Henan province, People's Republic of China. It borders the prefecture-level cities of Jiaozuo and Luoyang to the east and southwest respectively, as well as the province of Shanxi to the north.

Administration

The sub-prefecture-level city of Jiyuan administers 8 towns, 4 townships and 4 subdistricts. Jiyuan is named after the Ji river whose source is said to be a spring located on the west of the city.

History

Jiyuan was a county belonging to Jiaozuo City in the past, then it was divided from the city. Jishui River, one of the ancient "Four Rivers" with the Yangzi River, Yellow River and Huai River, originates from Jiyuan, literally the source of Jishui, hence deriving its name. According to the latest archaeological findings, as early as around 10,000 years ago, precisely at the end of the Paleolithic Period and the beginning of the Neolithic Period, people have lived here. It used to be the capital of the Xia Dynasty and was well known for its wealth between the Period of Warring States and Han Dynasty.

High frequency

High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 MHz. It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred metres). Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances. The band is used by international shortwave broadcasting stations (2.310 - 25.820 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.