Land mobile radio questions? - longest range uhf
Although I prefer a long detailed answers if you know the answer to a question, please answer! Thank you for your help.
BTW I have this question in this section because I think these will be used by police officers.
What is the VHF and UHF? What kind of job can most systems to 4.5 watts or? Who mainly uses these systems? I need a license to operate them? Should I expect that some problems due to interference of the small number of channels?
Saturday, February 13, 2010
Longest Range Uhf Land Mobile Radio Questions?
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VHF very high frequency band and represents the mean from 30 to 300 MHz UHF (Ultra High Frequency) band from 300 MHz to 3 GHz
The allocation of land mobile bands exist in these two bands. In the United States, many missions LMR VHF. () especially at the lower end. In UHF, there are only a few. LMR systems are narrow band, generally attributed to the 12.5 kHz channel spacing. Sometimes half.
You need a license to operate them. The channel is assigned to a user, are mostly limited to other users on the same channel to enable. Some terrestrial channels as secondary users a priority for the government and the use of security products. In this case, you should be the state of quiet canals and avoid walking in the transmission of another person.
They are usually for fleet management and the things of this kind, where the voice or data are immediately required frequent contact and communication are usually short.
Depending on the antenna and you're on a cell phone or a mobile communications base, the range may vary considerably. Communication is normally line of sight or near a beach on flat ground without obstacles around 3 or 4 miles from phone to phone in the VHF band. The mobile base is better because they have a base of a tower, so the attenuation of the ground near the base of the antenna. In addition, a base of the antenna can be built, the supply of management, or provide a omni court) (image of a line-shaped cake.
With a high tower, you can manageR mobile / base, probably 20 miles in a favorable context. Torres still have more of a major power as well as borders.
The surgery is not really a problem in most of these stations, because their use is somewhat limited. His co-channel interference. It is a question of who is affected in its channel. About the adjacent channel and is strongly (typically 60 dB for adjacent channels and 80 +, unlike non-adjacent).
GMRS is around 460 MHz and is similar in other ways. It also requires a license. There are several GMRS users, so that the possibility of co-channel interference is quite high. However, radios are cheap and easier to acquire licenses because you do not solely or partially non-exclusive use of the chain.
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