My setup is very similar to Josh's up above using the MX275
Connected to battery positive in the aux switch harness under the Jeep gladiator's glove box area. Ground is to a grounding post in the passenger kick panel.
I am using a similar cowl mount for the 3db and 6db antenna (I swap them out depending on application).
I get a slight whine when ignition is in accessory or run. It does not appear to be variable with RPM. Just a slight whine. Antenna is not grounded
I have tried ferrite coils, etc with no luck.
For you jeep guys, what was the ultimate solution?