Thanks for all replies

> What value of series resistor between the pin and the outside

Switch wipers have 10k + 47n to ground/0V. Switch terminals go
directly to 12V or ground/0V. Wipers to PIC pins via 470R

> Do you have a bypass cap right at that pin?

47n + 5V1 ZD + BAT46 Shottky about an inch from the PIC (as
close as I can get them)

> My input networks consist of the pull-up or pull-down resistor, then
> a 100K series R (all of that physically close to where the signal
> enters the enclosure) and 100n bypass cap right at the PIC

12V comes in through a 1N5404 + 47n to 0V. Other lines have
47n to 0V / grounded plug body

> I use things like ceramic feed-through capacitors and series
> LC networks only for gear that is going to live in strong RF
> environments (AM and FM broadcast transmitter sites) - better
> safe than sorry.

Too true. Based on previous testing of 10 units, RF interference
is unexpected, although it's more of a nuisance than a safety issue.
Still, not a good look is it ? If feed-throughs, ferrites or whatever
are needed then that's what'll have to be done. Especially if it's to
allow for sloppy radio installation that's out of my control. I should
be hearing soon whether the ferrite beads made a difference, and
it would be a good idea to drag the scope out to the airport to look
into it personally. Perhaps just bumping up from 470R is all that's
needed

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