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Dear All ,
In my Ropex transmitter I
have a class D PA with 2 power fets Fairchild RFP 70N06 with rather
generous ratings 70 Amps each and a max voltage of 60 Volts the supply
voltage is 13.8 Volts and a measured output of 154 Watts . When the antenna is
mismatched for whatever reason will the Fets break down on voltage or
current peaks ? ( the DC input of 13.8 Volts is properly fused ) and
is it possible to prevent voltage breakdown by fitting power zener diodes over
the drain and source of both Fets without spoiling their efficiency
. A fast overcurrentprotection is included in the circuit . The reason
for this question is that we had a breakdown in the Ropex Fet final of
PA0VHF while tuning the antenna matching unit out of resonance ( while doing
this the input was rather low ) and are wondering what caused it .( The heatsink
was not hot at all while tuning up to the rated output
)
73,William
PA0WFO
----- Original Message -----
Sent: Saturday, February 04, 2006 2:03
AM
Subject: LF: Re: More smoke...
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