[Elecraft] K3: Added protection for RS-232 port

[Pete Smith]

I've been thinking about how one might go about adding some protection 
for the apparently fragile (and expensive) RS-232 port on the K3.  It 
might be possible, if the components were small enough, to add them on 
the KIO3 I/O daughterboard, or perhaps on a little external board 
mounted at the port.

But the question is, what components?  I have seen small gas tube units, 
but suspect that by the time the potential reaches 90 volts or so and 
the tube flashes over, the RS-232 transceiver is probably toast anyway.  
Would it be feasible to use fast diodes to shunt the data lines to 
ground at .7 volts or so, or would that introduce other problems (stray 
capacitance, etc.)?  Anything else that might make sense?

-- 
73, Pete N4ZR

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