Should I install ferrite beads on KIO2/AUX2 cable?

[Dave Mueller-3]

It's been a while since I've built anything, so I'm starting small with the accessory boards for the
K2.  I finished the KIO2 and AUX2 boards and am getting ready to prepare the connecting cable.  I
have a bunch of 43 and 73 mix ferrite beads that I use in all of my RS232 cables.  I've read a few
posts in the archives about noise.  Should I bother putting the beads on the cable?  Any suggestions
as to which end of the cable (ie should I expect more noise coming in from the DB9 or coming off of
the control board)?  At this point, I'll thinking about the 43's at the DB9 end, and the 73's at the
control board end.

Thanks,
Dave AA3EE
S/N Not yet!
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[Don Wilhelm-3]

Dave,

I would not see any advantage in adding ferrite beads to the cable inside
the K2, but if you want to add beads on the cable that connects to the
computer, thay may be a good idea.  I would say to put them on the computer
end if you only use one, but both ends would be OK.  The noise problem (if
any) will eminate from the computer, so stopping it at the source would
perhaps be beneficial.

There are other signals in the cable inside the K2 and these 'K2 specific'
signals also appear at pins on the AUX I/O connector.  There are no RS232
level signals inside the K2 beyond the short connection between the DE9
connector and the MAX1408 IC - the internal cable carries both analog and
CMOS level digital signals.

I recommend that any references to the DE9 connector on the K2 use the 'AUX
I/O' designation as printed on the panel.  THIS IS NOT AN RS232 CONNECTOR,
it does contain 3 RS232 level signals: TXD, RXD and Signal Ground.  That
thought process may help prevent folks from plugging a 'standard' computer
serial cable into the K2 AUX I/O connector and causing extensive damage to
the K2.

Notice that the K2 to computer cable contains only 3 signal wires and the
shield is to be connected only at the K2 end - this is to keep noise on the
computer chassis from being conducted to the K2.

73,
Don W3FPR

> -----Original Message-----
>
> It's been a while since I've built anything, so I'm starting
> small with the accessory boards for the
> K2.  I finished the KIO2 and AUX2 boards and am getting ready to
> prepare the connecting cable.  I
> have a bunch of 43 and 73 mix ferrite beads that I use in all of
> my RS232 cables.  I've read a few
> posts in the archives about noise.  Should I bother putting the
> beads on the cable?  Any suggestions
> as to which end of the cable (ie should I expect more noise
> coming in from the DB9 or coming off of
> the control board)?  At this point, I'll thinking about the 43's
> at the DB9 end, and the 73's at the
> control board end.
>
> Thanks,
> Dave AA3EE
> S/N Not yet!
>

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