How to utilize several different main amateur band ?
160m band (1.8-2.0MHz)
This is an amateur frequency band belonging to the medium wave (MF) band. It should be remembered that the predecessors of amateur radio communication made great contributions to humanity from these low frequencies.
The radio waves in this frequency band are mainly propagated by ground waves. Generally speaking, the maximum distance of ground wave propagation is only 250km. Therefore, in the general years of sunspot activity, this frequency band can only be used for communication between local and nearby areas. But extensive practice has shown that within one or two hours before dawn in winter, and within an hour before the sun sets, it may spread thousands of kilometers away. The various 160m band international competitions held in January and February each year provide a great stage for enthusiasts who are passionate about communication in this band to showcase their skills.
There are some differences in the classification and use of this frequency band among countries, such as China, the United States, and the United Kingdom, which use 1.8-2.0MHz, Australia, which uses 1.8-1.860MHz, and New Zealand, which uses 1.803-1.813MHz and 1.875-1.900MHz. Therefore, we often need to use the “different frequency operation” method to compensate for the differences in regulations among countries. For example, if we want to contact Australia, we can transmit at frequencies higher than 1.860MHz and listen at frequencies lower than 1.860MHz.
80m band (3.5~3.9MHz)
This is the amateur frequency band with the lowest frequency in the HF band, and it is also the most advantageous frequency band for beginners to make their own transceiver devices at a lower cost. Like the 160m band, it generally relies on ground waves for propagation, ensuring better communication with neighboring countries at night. In years when sunspot activity is relatively calm, the effect of DX at night is quite good, and during the day, it can sometimes reach up to 300km away due to ionospheric reflections.
It should be noted that 3.735MHz is the internationally designated Slow Scan Television (SSTV) channel.
Both the 80m and 160m bands are subject to lightning interference within several hundred kilometers and interference from non amateur radio stations during summer.
40m band (7.0~7.1MHz)
This is a dedicated amateur band. In years with low levels of sunspot activity, this daytime band can be well used for communication between amateur radio stations within or near provinces. During the peak year of sunspot activity, it is possible that only local radio stations can be contacted. At night or in the evening and early morning, you can connect with radio stations around the world on this frequency band.
The regulations for this frequency band vary from country to country. For example, the United States can use 7.0-7.3MHz, of which 7.15-7.3MHz can be used for voice (speech) work, while IARU Region 3 can only use 7.0-7.2MHz. Mainland China and the Macao Special Administrative Region use 7.0-7.2MHz, while the Hong Kong Special Administrative Region does not open this frequency band to amateur services.
20m band (14.0~14.35MHz)
This is one of the most commonly used “golden” frequency bands by enthusiasts, and many countries require a high-level license to operate on this frequency band. Whether it’s day or night, even during the peak of sunspot activity, this band can still be used to communicate with people around the world. Unlike the previously introduced frequency band, this band has begun to exhibit a “distance crossing phenomenon”, where a ground wave cannot reach and a sky wave surpasses the previous “silent zone” that cannot be reached by radio waves in a single hop. This is a unique phenomenon of celestial wave propagation. The main issue affected by the phenomenon of crossing distance is the communication between radio stations within the province or neighboring provinces, such as Beijing and Tianjin, Nanjing and Zhenjiang, Suzhou, Shanghai, etc., which cannot use the 20m band for communication in most cases. However, due to the constantly changing ionosphere, the range of the quiet zone is not fixed and unchanging.
15m band (21.0~21.45MHz)
This is the busiest frequency band, and a large number of beginners around the world are also active in this frequency band. During the low period of sunspot activity, the 15m band can be well used for remote communication, and even during the peak period of sunspot activity, it is relatively reliable. Moreover, it often complements the 20m band, for example, when communication with Europe and America was not good on the 20m band, communication improved on the 15m band.
The phenomenon of crossing the distance in the 15m band is more pronounced, especially in the winter and summer seasons, when it is difficult to listen to local or domestic radio stations.
There are many low-power radio stations active on this frequency band. Japan has allocated 24 channels in the frequency range of 21.210-21.440MHz specifically for low-power radio stations below 5W.
10m band (28.0~29.7MHz)
This is an ideal low-power long-distance communication band, even during the peak of sunspot activity. When this frequency band is activated (i.e. when the propagation is good), it can achieve communication effects similar to making a phone call.
Due to its high frequency, the lower density of the ionosphere at night cannot reflect it, so remote communication in this frequency band is generally only possible during the day. The antenna equipment in the 10m band is the smallest in size among all shortwave waves, and its diffraction ability during propagation is stronger than that of ultra shortwave waves. Therefore, many enthusiasts use this band for mobile communication at medium and close distances.
On the 10m band, 28.0~28.2MHz is generally used for telegrams, 28.2~28.25MHz is a worldwide amateur radio beacon in the 10m band, 28.25MHz and above are generally used for voice communication, and 29.4~29.5MHz is a frequency used for amateur satellite communication.
6m band (50~54MHz)
The 6m band belongs to the VHF (very high frequency) band, and its propagation mode is similar to light waves, ensuring reliable communication within the line of sight range. Many countries have a 6m band automatic transfer system shared by enthusiasts, such as Australia where enthusiasts can use handheld walkie talkies for communication around Australia.
People have found in a large number of communication experiments that 6m waves can also be used for long-distance communication. For example, enthusiasts in Suzhou, China have contacted amateur radio stations in dozens of countries such as Australia on this band; For example, Australian enthusiasts often receive a signal (48.5-56.5MHz) from Jiangsu TV Channel One in their local area. What’s going on? This is because in the troposphere at the bottom of the atmosphere, various climate phenomena generate circulation of cold and hot air masses, while the upper stratosphere is not affected by them. The unevenness of this atmospheric physical property changes the direction of very high frequency radio waves, causing them to propagate along the “interlayer” between the troposphere and stratosphere towards distant places. This phenomenon is also known as the ‘atmospheric duct’. In the microwave band, the transmission of electromagnetic waves often requires a device called a “waveguide”. The inner wall of this metal tube is as bright as a mirror, and electromagnetic waves continuously reflect and jump forward from the tube wall inside. This is very similar to what we call ‘tropospheric propagation’. Of course, this phenomenon known as “tropospheric propagation” is influenced by meteorology, so the duration of each occurrence is not very long.
Modern science has shown that there are areas of uneven electron density at the bottom of the E-layer of the ionosphere, which have good scattering effects on radio waves with frequencies of 40-60MHz. Their range of action is 1000-2200km, and they exhibit fading phenomena but are not affected by ionospheric disturbances. Modern science has also proven that billions of meteors enter the atmosphere every day and night. These meteors burn up at an altitude of 80-120km, forming a thin and long column of ionized gas that rapidly spreads. This is also a good radio medium for radio waves with a working frequency of 20-100MHz. Moreover, due to the high scattering point of this “meteor trail”, its effective distance can reach over 2000km.
2m band (144~148MHz)
This also belongs to the very high frequency band, and its propagation relies more on direct waves. Enthusiasts mainly use this frequency band for communication within their local area. Many countries have built an automatic differential system called a “repeater” on this band, and enthusiasts can use their handheld devices to communicate over long distances through its differential. China’s BYIPK once used this device and successfully conducted contact experiments between the Great Wall, BYIPK (near the Temple of Heaven Park in Beijing), and the United States for handheld walkie talkies and walkie talkies through international long-distance transfer.
The 2m band, like the 6m band, also has an incredible long-distance contact record of nearly 7000km. The air masses or different temperature layers caused by climate form “tropospheric propagation”, and the sudden E-layer also creates conditions for long-distance propagation in the 2m band. Compared with the 6m band, the tropospheric propagation in this band is more affected by climate change, and the possibility of utilizing the sudden E-layer is also greater.
The 2m band is a commonly used band for amateur enthusiasts to conduct various space communication experiments. The downlink frequency of the amateur satellite uses this frequency band, with 145.810MHz and 145.990MHz being the beacon transmission frequencies of the amateur satellite “Oscar 10”; The “EME” experiment using lunar reflection for communication has also been conducted in the 2m band, and so on.
70cm band (430~440MHz)
The 70cm band belonging to UHF is the “golden channel” for land mobile communication. Compared with the 2m band, the 70cm band antenna can be more compact, with relatively less interference, and can use a wider frequency band. The communication effect in urban areas is also good, so it is particularly favored by mobile communication enthusiasts. Many cities in our country have relay stations in the 70cm band, which greatly facilitates mobile communication experiments for enthusiasts.
Although 70cm band communication mainly relies on direct waves, it is also possible to achieve long-distance communication under special weather conditions. Foreign enthusiasts have set records for land communication distance of over 2200 kilometers and surface communication distance of over 4000 kilometers using the 70cm band. In addition, amateur communication satellites often use this frequency band.
It should be noted that amateur services are in a secondary position in the 70cm frequency band, and we cannot affect the normal use of other service radio stations in this frequency band during use.