What is a VHF/UHF Repeater in Amateur Radio?

Unlike High Frequency (HF) signals, VHF/UHF (Very High Frequency/Ultra High Frequency) signals travel in ‘line of sight’ or rather a take a straight line path. In case of HF there is a ground wave which covers locally and a sky wave which bounces off the ionosphere, giving them a large range globally. But the range VHF/UHF transceivers are limited on simplex operation. To enhance the range we need repeaters which are transceivers which receive the signal and retransmit on a different frequency.
In case of VHF in my locality, the usual shift is -600 KHz, that is the difference between the two frequencies. The repeater also amplifies the received signal before retransmitting. Higher shifts are used in UHF and microwave bands, which I have not operated on! So while working through repeater, the transceiver has to be on duplex mode with a difference between the transmitted and received frequencies as set by the repeater. The shift is required to prevent the repeater’s receiver being drowned by its own transmitted signal as both operate continuously.
Web: johnsonfrancis.org/techworld/...

[@KN4YEM]

Thanks Again , India lets get going.

[@johnsonstechworld]

Welcome!

[@siddharth4662]

I have a question.... My UHF Repeater for HAM was working absolutely fine for the past 5 years till a couple of days ago it started acting weird.... The repeater now gets triggered only from certain locations... This happened suddenly on its own. Just unable to trouble shoot the issue. Using 2 Motorola PRO5100 radios.

[@johnsonstechworld]

I do not have a specific answer for your question. Has there been any change in the antenna parameters? You may want to post it on qrz.com forum which I have found very useful for getting answers. forums.qrz.com/index.php

[@siddharth4662]

@@johnsonstechworld thanks for the answer. Will post on QRZ

[@johnsonstechworld]

Talked to the repeater custodian in my region. He is of the opinion that antenna and cable system needs attention. Rain water seeping into the cable is a likely concern. In our region, antenna and cable system usually does a good job only for about 2 years.

[@johnsonstechworld]

Hope you have already checked the antenna and cables. 73 de Jon, VU2JO

[@siddharth4662]

I will check the feedline.