[Amps] Pin Diodes

[Rob & Terri Sherwood]

It is interesting that Alpha threw in the towel on PIN diodes with the 
upcoming 9500.  Tech support told me the yield on a batch of diodes was 
terrible, possibly as low as 30%.  That is a shame, as my Alpha 89 
(manual-tune version of the 87A) has PIN diode switching, and is a 
wonderful QSK amp.  I don't believe an amp with vacuum relay T/R 
switching can be considered a full QSK amp.   Yet Alpha advertises the 
99 and the 9500 as full QSK.   I run my 99 in semi-breakin only. How 
long can a vacuum relay last in full QSK mode?   There must be a maximum 
keying rate and a typical cycle life for anything mechanical.  Are they 
banking on the fact that semi-breakin is usually adequate?