Re: signal leads that pick up less ambient noise?

On 26/02/2025 4:39 am, Christopher Howard wrote:

Bill Sloman <bill.sloman@ieee.org> writes:
 

On 25/02/2025 4:46 am, Christopher Howard wrote:

Google for coaxial feed through capacitors.

Capacitors and resistors don't ring. Adding inductance can introduce
ringing. but enough resistance can make the resonant circuit
critically damped and the voltages and current will decay
monotonically.

 So, when you use a coaxial feed through capacitors on your Faraday cage,
do you add a resistor right after the capacitor, to reduce/eliminate
ringing?

The whole point about coaxial connectors is that the distributed capacitance and inductance gives you a R50R transmission line. The only way to get "ringing" out of that is to fail to terminate the transmission line with  it's characteristic impedance. In practice it is hard to do it perfectly and you do tend to get low level reflections, but they die out fast,

Or are you just trying that all your inputs on the board have
resistors before whatever op amps or other components that they feed
into?

The message is rather more complicated than that. The later editions of Ralph Morrison's book do go into that in more detail than the earlier editions.
--
Bill Sloman, Sydney