In the same way, your wireless connection and performance will degrade somewhat as the distance between your Router connected devices increases. This may or may not be noticeable to you. As you move further from your Router, connection speed may decrease. Factors that can weaken signals simply ...
Interestingly we hooked up a Draytek Vigor 120 and that seemed pretty happy at a much lower SN of 5 or 6. It also seems that the customer site is on the distance limit from the exchange. So I think it is fair to say that this problem was the SN ratio as suggested initially by L...