I've had this problem for some time now.

Basically, when the stereo is turned on, it makes these full volume heartbeat like sounds every few seconds. These sounds are independent of volume and source (i.e. it's always the same intensity, and it happens if it's on the radio, CD etc.) I can hear whatever is playing between the beats.

Has anyone encountered this before, and could someone suggest steps for diagnosing the problem?

2003, S40. HU-615.

Edit: Also, my antenna is bent, could that have something to do with it? I've tried by disconnecting the antenna connector, but it still makes the sound.

I'd appreciate any help, thanks in advance.