I think you'll find - that the Bee sting aerial is for FM only.
The head unit will have a ferrite bar inside for AM frequencies.
Maybe you have a gash receiver?
I think that used to be the case but not so now.......certainly with my Audi which uses the same part number aerial as the Golf. Have a read of this:-
'If you have problems with radio reception don't be quick to blame the head unit; the problem my lie with the radio antenna. The OEM factory antenna employs separate amplifier circuits for the AM and FM bands. These circuits are designed to boost the most radio signals possible while filtering out unwanted stations and noise. These microelectronic circuits are housed in the antenna's base while the receiving element consists of a spring loaded, wire-wound, fiberglass mast designed to withstand most automatic carwash machinery.
Symptoms of problems with radio reception include poor FM reception (only strong stations tune in), and virtually no AM reception. Other indications of faulty antenna operation include audible "pops" heard on the AM band originating from turn signal or windshield wiper relays. The culprit to these problems may be that the antenna is not getting 12 volt power, the antenna is poorly grounded, or the antenna amplifier may be bad. The worst case scenario is that none of these problems is the cause and the radio itself is bad. If you have an aftermarket radio, the antenna may not be receiving power or you may have an ill-fitting antenna RF cable adaptor. Regardless, to troubleshoot for the source of the cause will require gaining access to the antenna and power connections at the back of the head unit and at the base of the antenna.'
This article came from here:-
http://20v.org/audioupg.htm#antenna