I was having this issue with a JVC deck that came with my '92 loyale where the FM reception would gradually fade until I smacked the radio, and then it was good again for a minute before fading again. I figured it must be a deck issue since smacking the radio probably wouldn't fix an antenna issue. However I finally got a new deck, but the problem remains.

 

What would cause this gradual signal loss? Does the antenna jack need to be replaced? I inspected the antenna cable and saw no signs of damage.

it wasnt a subaru that had the problem, but i've had it... it was the wire, it had broken right where it met the antenna... usually from pulling/trying to get the antenna to reach the deck's antenna port

 

i've noticed it's slightly hard to get a deck in there without an antenna cord extender (on my soob at least) but they're pretty cheap... makes it a lot easier to remove/install the deck too

...Also: a "Grounding" antenna Wire can do that... Check the Wire, and see if it´s Not Groundin´

Good Luck!

I'll just pull the whole antenna out and take a good look...

 

as far as grounding....do you want the antenna grounded, or is that a bad thing?

The antenna element itself needs to be isolated from ground. It picks up the signal. The base of the antenna is grounded and the car chassis becomes part of the antenna design. The shield of the coax ties to the antenna base which is grounded. The center conductor of the coax is tied to the antenna element which is isolated from ground. The center conductor of the coax may have a bad solder or crimp connection to the center connector.

Can anyone tell me how you remove the antenna on th 86 Subarus?

I'll just pull the whole antenna out and take a good look...

 

as far as grounding....do you want the antenna grounded, or is that a bad thing?

The center conductor goes to the antenna and the shield goes to ground,

They both need a good connect to complete the circuit.