5.8GHz analog FPV video signals cover a static frequency. They are not "smart" about their bandwidth use, as e.g. a typical 2.4GHz RC link, or a WiFi signal.
When you fly FPV and someone close to you also transmits on the same channel, both of you will might experience reception problems.
To avoid stomping on each others signals, you need to space out your channels as far as possible.
The channel allocation in 5.8GHz is very convoluted and redundant, so instead of looking at the channel and band number, I suggest to compare frequencies.
Look at how much bandwidth you have available, check how many pilots want to fly at the same time, and then spread out channels evenly, with as much free space between them as possible.
E.g. in Australia, we can only use the middle of the band. We want to have 4 pilots.
The maximum spacing we can get is 20MHz.
So we usually use these 4 channels: 5.740 (F1), 5.780 (F3), 5.820 (F5), 5.860 (F7) and we limit the power output to 25mW. The above frequencies and power output is legal in most places, but always check your local laws!
If you can throw a few buck together or get you local club to buy one, a RFExplorer is a great tool for channel management!
Since you read all the way down here, maybe you are interested in
this article about the cost of FPV! Read on..