I would recommend skipping wireless all together. You will still need power to them, so wireless is really a misnomer. Best way is to run siamese coax to all of your cameras from a central power supply. It may be a little more work as far as cabling, but you can then put a UPS on the power supply and DVR to keep them up for a while in the event of a power outage. It's also a pain to have power adapters scattered all over. If you are going to have any cameras away from the main structure, you will want to bury the cable. Otherwise, lightning will not be your friend.
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