There are two main solutions for using mobile signal repeaters to cover tunnels :  Fiber optic repeaters : these repeaters use fiber optic cables to transimit the signal from the cell phone tower to the tunnel .fiber optical cables are less susceptitle to signal attenuation than copper cables,making them ideal for use in tunnels .  DAS(distributed antenna system ):this is a more complex solution that involves installing a series of antennas and amplifiers throughout the tunnel . DAS systems can provide better coverage than fiber optic repeaters .but they are also more expensive to install and maintain

Talk to other ham radio operators: Other ham radio operators can give you valuable advice on choosing the right repeater. They can tell you about their experiences with different repeaters and can help you to find a repeater that meets your needs.

Contact the repeater owner: If you are still experiencing interference or weak signals after trying these steps, contact the owner of the repeater station. They may be able to help you to troubleshoot the problem and find a solution.

A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. Linearity refers to the ability of the amplifier to produce signals that are accurate copies of the input.

Sometimes, our mobile phone has poor signal reception in our house, the reasons are as below: Distance from the nearest cell tower. The farther away you are from a cell tower, the weaker the signal will be. If you live in a rural area or in a valley, you may be further away from cell towers, which can cause poor reception. Building materials. Some building materials, such as concrete, brick, and metal, can block cell signals. If your home is made of these materials, it can make it difficult to get a good signal.