Larry, I thought maybe my 20-year old Sylvania and RCA replacement crossreferences would help, but only similar numbers come up, e.g. AG30 or AJ20. They happen to be diodes, and the replacement recommendation is a general purpose 1A silicon, sort of like a 1N4007 or such.

Can't envision a use for a diode like this in the antenna circuit, and what you describe sounds like something in an expensive communications receiver (sort of like Motorola's "Extender" which was a near band AM noise receiver used to turn off the IF gain during noise pulses), which would learn me a new one if these are used in car radios.

If it was a back-to-back package, I'd guess it was high voltage protection for the front end mixer (again, can't picture a volvo radio with an rf gain stage...) and probably schottky. If it's a 3-terminal package, maybe its a dual pin diode that is used for AGC and feedback noise reduction, but that would have its common point wired to a biasing circuit and would act as you describe with the diodes removed.

Can you post the Volvo model of the radio, like CR-xxx, maybe I have one. I enjoy flipping circuit boards back and forth to reverse engineer them as much as anyone.