Ten things you didn't know about RF.

A portable antenna has a gain of between 0 and -9dBi

A repeater installed on top of a building provides coverage to mobile radio users for about 100km. The power on this repeater is set at 25W. Increasing the power to 50W will increase the coverage for these users.

Using a duplexer will help filter out inference on a high-site?

VHF will always provide better coverage than UHF?

A new Motorola two-way radio does not require alignment.

An antenna which has 9dBi gain is better than a similar antenna which has 6dBd gain.

Installing a repeater on top of a mountain or building does not always provide the best coverage?

Adding PL will not solve interference problems on a repeater which uses carrier squelch.

It is okay to use nickel-plated nuts and bolts on an Aluminium mast.

You have a site with four repeaters in the same frequency band. It is better to use separate antennas and duplexers since the losses will be minimal, and the costs low, when compared to other options.