亚博绑定银行卡有危险吗there are many different forms of radio propagation that can be used for amateur radio contacts. some utilise the more normal forms of radio propagation, and the procedures, frequencies and the like are well know. however other forms of propagation are less widely used, or they may occur occasionally and more specialist procedures, specific frequencies and other requirements may be needed.
it is the operating procedures, frequencies and techniques that are described in this series of pages.
Amateur radio propagation modes used.
one of the interesting aspects of ham radio, is the enormous variety of different propagating modes that can be used.
亚博绑定银行卡有危险吗the band, time of day, time of year, weather and position in the sunspot cycle can all have an effect, dependent upon the type of propagation mode used.
knowing how to anticipate the different forms of propagation can help ensure that the best chances are presented. then knowing the different operating procedures along with the frequencies, and optimum modes can ensure that the best chance of making contacts is gained.
some of the main forms of propagation are detailed below:
- Ground wave propagation: Although ground wave propagation is used for the medium and long wave broadcast bands, it is not particularly widely used for ham radio communications. It is used on 160 metres and 80 metres, but in view of the fact that with increasing frequency signals propagating via this mode are increasingly attenuated, it is not particularly widely used.
Note on Ground Wave propagation:
ground wave propagation occurs when signals follow the contour of the earth, bending so that the signals are able to be detected beyond the horizon. it is this form of propagation that is used by lf and mf, long wave and medium wave band broadcast stations..
Read more about Ground Wave propagation
- Ionospheric propagation: Ionospheric propagation is the form of propagation that is widely used on the short wave amateur bands. Using refractions of the signals via the ionosphere it is possible for global communications to be gained. To make the most of these bands, the use of propagation charts as well as looking at the ionospheric indicators provides a good understanding of what is happening. However it is also essential to have a good ”feel” for the different bands.
Note on Ionospheric propagation:
亚博绑定银行卡有危险吗the ionosphere exists in the upper reaches of the atmosphere extending to altitudes of 400 km or more. the different regions of the ionosphere can affect radio signals refracting them so that they return to earth. in this way, signals can be heard at distances ranging from a few hundred kilometres to the other side of the globe.
Read more about Ionospheric propagation
- Grey line propagation: One form of propagation that can yield some amazing results is called grey line propagation. If a signal path follows the shadow line between dark and light, it receives significant enhancements, and it can be used to very good advantage if used with a little inside understanding.
- Tropospheric propagation : Tropospheric propagation is normally associated with the VHF and UHF amateur bands. It occurs when there is a sharp change in the refractive index of the air with increasing height. This can be associated with weather front and as such a good eye on the weather can be very helpful.
Note on Tropospheric propagation:
the troposphere is the region of the atmosphere closest to the earth. it is found that the refractive index of the air reduces slightly with increasing altitude. this effect can also be enhanced and modified by weather conditions. as electromagnetic waves bend towards the areas of high refractive index, it is found that radio signals are affected by these changes and can travel over distances beyond the horizon.
Read more about Tropospheric propagation
- Sporadic E, Es propagation : Sporadic E occurs when very dense areas of ionisation form in the E region of the ionosphere. It can affect frequencies from low in the HF ham radio bands, but it is more noticeable where there is no normal ionospheric propagation. As such frequencies at the top of the HF band spectrum and into the VHF spectrum can benefit from its occurrence. As the name indicates it occurs sporadically.
Read more about . . . . how to use amateur radio sporadic E, Es for ham radio.
- Meteor scatter: Meteor scatter propagation is a rather more specialist form of radio propagation for ham radio. It uses the reflections from ionisation caused by meteors entering the Earth’s atmosphere and burning up. In view of the short life of the trails, communication is intermittent lasting only a second or more each time a meteor enters the atmosphere. It used to require very fast Morse transmissions, but these days other data modes are available and widely used.
Read more about . . . . how to use amateur radio meteor scatter.
- Auroral propagation: At some stages the Sun throws out vast quantities of material which can come towards the Earth and cause geomagnetic storms. When this occurs the HF bands can be blacked out as the D region ionisation rises and absorbs signals. However the auroral regions also become highly ionised and can support VHF and sometimes UHF propagation
Read more about . . . . how to use auroral-propagation in ham radio.
- Moonbounce, Earth-Moon-Earth, EME : One unusual form of radio propagation is to use the Moon as a reflector. Large antenna gains are needed as the path losses are huge, so parabolic reflectors are often used. Occasionally multiple stacked Yagis have been used. High powers and specialist procedures are needed.
Read more about . . . . how to use moonbounce for ham radio.
More Ham Radio Topics:
What is ham radio Callsigns Morse code Voice modes Digital data modes QRP operating Codes & abbreviations Ham bands overview Operating via differnet propagation modes Repeaters Callsigns Contact formats Setting up a shack & buying equipment
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