Line of sight is no longer possible because something is blocking the radio. Often in these situations, a radio that can repeat the message is placed on the top of the mountain, called a repeater or base station. If a user wants to make a call on the handheld radio, the message goes in a straight line up to the repeater.
The repeater needs to receive the frequency that the caller transmitted with, and then the repeater re-transmits that same message down to the user on the other side of the mountain.
It works similarly to the satellite discussed with VHF radio propagation, but instead of a satellite, it is a fixed radio on top of the hill. This site uses both functional cookies and tracking cookies to help us understand how users interact with the site. You can choose to disable non-functional cookies if you wish, however we will need to set a functional cookie to respect your choice.
We use trusted third-party analytics providers to help us improve your experience on this website. Radio Academy. Login Register Search. Topic Progress:. Course lessons. A typical repeater has five components: antenna, duplexer, receiver, baseband processor, and transmitter. The duplexer allows a single antenna to both receive the signal on one frequency and transmit the signal on another. The receiver filters and amplifies a low level signal and so it can be processed and sent to the transmitter.
How does a digital repeater differ from an analog repeater? The main difference is in the baseband processor. In an analog repeater, the receiver voice is filtered and sent directly to the transmitter modulator. Any noise received will be sent to the transmitter. Whatever a radio receives, this repeater downlink will have noise additions from both the uplink to the repeater and the downlink from the repeater. In the digital repeater, the baseband processor converts to binary bits which get error corrected and then sent to the transmitter.
The radio receiving the repeater will also error correct this downlink signal resulting in noise free voice. Only when the signal gets too weak in either the uplink or downlink does the voice decode start to break up and drop out. Do I need a license? Typically the repeater receives on the higher frequency and transmits on the lower frequency.
This can be reversed if needed by swapping cables inside and re-tuning if necessary. How can I improve range?
By using higher antenna gain, more power on the transmitter, or better antenna location. An engineer will visit your site and replace the faulty repeater with a loan unit to ensure your system is back up and running as quickly as possible. This is invaluable, as without the repeater the radio system is ineffective and down-time with any form of communication costs businesses money. Contact us for more information and expert advice about repeaters for mobile or portable radios.
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