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The FT-736R SAT switch can zap pre-amps.

The 736R SAT switch has break-before-make contacts, which meanhat in between
 switch positions the circuit is the same as if the SAT switch is in the OFF po
sition.  If you have set up one of the modules to transmit for non-satellite op
erations (i.e., w
hen SAT switch is OFF), that module will be enabled between the RX-TX-NOR-REV p
ositions of the SAT switch.f you are transmitting while you move the SAT swi
tch between these positions you may accidently key up the unintended module and
 send a burst of
RF down the antenna line into your pre-amp.

For example:  VFO A happens to be set to operate on 2 meter FM.  You don't give
 this a second thought, since you are working Mode B CW with the SAT switch ON.
  You are listening on 2 meters and keying your 70 CM transmitter trying tor
o your downlink f
requency.  Changing the SAT switch positions under these conditions is perfectl
y normal.

However, if you happen to send a dot or dash during the open interval been s
witch positions it is not your 70 CM transmitter that gets keyed but your 2 met
er FM transmitter.  This sends a burst of RF down the 2 meter coax that you hav
e configured for
receiving.  If you have in that coax a preamp without adequate RF-sensed pin-di
ode switching, then say goodbye to the GaAsFETs in the preamp.

If you are using the FT-736R preamp switch and the 12 VDC on the coax to operat
e coax relays at the preamp,  you might be lucky -- if the relays drop out fast
 enough.   I don't know if the control circuits operate fast enough to take car
e of this transie
nt condition, but I doubt it.

This cost me two MGF-1402 GaAsFETs in my unprotected homebrew 2 meter preamp be
fore I realized that they both departed this world under exactly the same circu
mstances of operation of the SAT switch while sending.  Although I was on CW, t
he same thing cou
ld happen on SSB if you happened to be speaking and the VOX were to be operated
 during the switch rotation.

Thanks to John, KL7GRF, for clueing me to the real problemhe SAT switch while t
ransmitting.
             (2) Use adequate RF sensed mp switching.