I used a TrendNet dual-band high-gain antenna and found that it did not increase signal. In fact, it seemed to actually introduce more noise and cause more disconnects than usual. This is all on the 5 GHz channel. The 2.4 GHz channels did get boosted a bit but I wasn't looking for that. The 2.4 GHz on the 855 is sufficient. It's the 5GHz channel that's appalling for a ~$300 router in terms of strength and distance.