[time-nuts] SMD TADD-1 distribution amplifier

[Charles Steinmetz]

Bruce wrote:

>Something like an annular ring capacitor that insulates the BNC body from the
>chassis whilst capacitively shorting it to the Chassis at RF ??.
>Followed by a freeite sleeve/bead arround the connector body or the coax
>connecting the signal from the connector to the PCB?

Back in the imagineering era of the various signal-egress abatement 
programs there were some connectors made like that (though not BNCs) 
-- in effect, the body of the connector was the center conductor of a 
feedthrough capacitor, and it in turn was drilled through for the 
insulator and center conductor as with any coax connector.  You used 
a big ferrite bead around the coax just ahead of the connector to 
provide some resistive inductance.  It was later shown that two SMT 
caps with very short loops worked just as well at all but the 
higheset frequencies (several tens of GHz and up).  I have since run 
into a few of the connectors at hamfests and university flea markets, 
but I haven't seen any new ones for decades.

Most equipment these days just uses non-isolated connectors, all 
placed in close proximity on the chassis and bonded tightly to 
it.  If you're careful with what goes on inside the box you won't 
*cause* any circulating ground current.  Of course, this won't fix a 
ground loop caused by another piece of equipment, but the prevailing 
theory is (and has been, for some decades) to identify and fix the 
malfeasor on a case-by-case basis rather than expect every piece of 
equipment to fix ground loops between other items that are connected to it.

Best regards,

Charles