This paper studies the reasoning of the Shannon equation in detail,it points out a casual hypothesis in Shannon s reasoning which results in the confliction with the UNB communication.

• 研究了乡农公式的推导；指出了乡农在推导过程中的一个不经意的假设；而恰恰是该假设导致了与目前超窄带通信的冲突.；提出了改进的办法；并将其运用于超窄带通信理论；得到了正确的结果