Splitting the antenna output to feed multiple receivers is fairly simple. If the signal is reasonably strong, you can use a cable TV splitter to divide the antenna feed to each receiver. Keep in mind the following:
1. Splitting the input reduces the output proportionately, minus an insertion loss. A 2-way splitter outputs slightly less than half of the input signal power to each output. A 4-way splitter outputs slightly less than one quarter of the signal power to each output.
2. Use all of the splitter outputs. If the splitter has more outputs than you have receivers, get a splitter with fewer outputs. Splitter loss isn't a big deal for strong signals, but for marginal ones it can make the difference between hearing the call and not.
3. There are amplified splitters that can boost the signal power at each output vs the input, but they tend to have bandwidth limitations that must be considered. An amplified splitter designed for UHF and VHF broadcast TV reception will work well for signals in those frequency ranges, but may completely block 800MHz signals. Passive splitters typically have an upper frequency limit, and will pass anything below that limit.
4. As has been mentioned, all of the above applies to receiving only. Connecting multiple transmitters to a single antenna without frying anything is much more difficult, complicated and expensive.