[Elecraft] KIO2 outside of K2

[W3FPR - Don Wilhelm]

Steve,

If the cable to the computer is built as specified in the KIO2 (or KPA100) 
instruction manual, noise pickup is minimized - the frame ground (pin 1) is 
connected only at the K2 end, and any noise on the computer frame ground is 
not conducted onto the cable.  I would expect any improvement gained by 
using optoisolators to be minimal - perhaps someone should try it and see.

Optoisolators are useful as a solution for ground loops in situations where 
they are likely to occur - such as instances when the connecting cable 
parameters are not known or specified.  One advantage to optoisolators is 
that separation of the signal ground in addition to frame ground is 
possible, but proper care must be exercised in the design to assure that 
this isolation is still present after the circuit is packaged (frame ground 
can be inadvertently made continuous even with the use of optoisolators by 
conduction through a metallic enclosure).

There is little advantage to be gained by separating the signal ground for 
RS-232 level signals unless the cable run is very long (more than 50 feet or 
so) and ground reference level shift creates a problem with the switching 
levels at the receiver.

For my $0.02 worth, I would not predict any improvement.

73,
Don W3FPR


----- Original Message ----- 

> Hi all,
> I noticed that the KIO2 option uses a standard conversion chip like the
> Maxim 232, but does not use optoisolators.  I guess the optoislators would
> not help when the KIO2 is inside the radio close to the other circuits.  I
> also noted that the KIO2 can generate noise. Has anyone ever considered
> using the KIO2 with optoisolators added outside of the K2 chassis?  My
> limited experience with my homebrew interface for a Kenwood CAT says that 
> it
> would be much easier to eliminate the interference, and since the cable to
> the computer is outside the radio, the RS232 interface being outside the
> radio would not be much of an inconvienience.  Just a thought.
>