Anyone repair stock antenna cable?

The reason that feedline is built like that is that it is VERY high impedance. This "gets into" deep theory even I've forgotten but the short answer is, an AM antenna "quarter wave" which would equate to a 9' "quarter wave" whip for say, CB radio, for AM would be not 9 ft, but HUNDREDS of feet. (550khz would be some odd 425 ft tall!!)

This causes the feed impedance of such a short antenna to be "off the map." In other words, they are not efficient

If you were to replace this with something more common, such as 52 ohm CB/ two way coax which is 50 ohms, or TV coax which is 70-75 some ohms, it would severely attenuate the AM signal