This is a very simple bit of code here, but I’m sure I’ll forget it myself one day, so for my sake here it goes.
SKSpriteNode* radar = [SKSpriteNode spriteNodeWithTexture:[SKTexture textureWithImageNamed:@"radar_lines"] size: CGSizeMake(105, 145 )];
radar.anchorPoint = CGPointMake(0, 0); //could be important, it was for my project
SKAction *oneRevolution = [SKAction rotateByAngle:-M_PI*2 duration: 5.0];
SKAction *repeat = [SKAction repeatActionForever:oneRevolution];
The SKActions are obviously what gets these radar lines rotating, but don’t overlook the anchorPoint property being changes from the default (0.5, 0.5) setting to (0,0) which anchors it in the bottom left of the image. Otherwise it would rotate around the center of the image (the image below should make that clear).