ac coupling

It doesn't make any difference.

Depends on the source level and relative impedances on the two sides of the capacitor. If the source could channel a lightning strike, I'd want the capacitor to blow up right next to the bulkhead feedthrough connector, where there's lots of grounded metal.

And if the capacitor connects to a high-impedance receiver, the receiver side is subject to spurious pickup and should be wired close. A sufficiently large capacitor, of course, would swamp the pickup current, BUT don't use one that big. Save your pennies.

Noise considerations would suggest that tracking to the first active node of the reciever be minimized. As a coupling capacitor is intended to look like a short at the frequencies communicated, it simply increases the effective pick-up area of the tracking wherever it is situated.

Singlre-fault abnormal implications would suggest that the capacitor be closest to the node that would be most physically damaged by a single fault to ground, or adjacent tracking. This could be either node, but the transmission side usually has greater potential circuit component loss under the abnormal fault, as it is configured to deliver power. This is an issue of recoverability, repairability.

Series resistor tracking can have a larger affect on nodes subjected to external noise sources than series coupling caps.

RL

Thanks. I initially thought that. But it got me thinking, and hence this question.

Thanks. Not an issue in my situation though.

This is what I thought. I'll have to check the receiver input impedance.

Thanks.