Bruce and Bryan,
Both the QCX and QMX series of radios have key click filtering that reduces the end-of-transmission spike that I believe is killing most QDX BS170s. The combination of high SWR and that last spike exceeds the limits of the BS170. If that is correct, adding the Zener(s) to the QCX or QMX will not hurt but will most likely not protect all SWR issues. A bad SWR can cause a high current or high voltage. The Zener protects against voltage failure.
73
Evan
AC9TU
