Radio in broadcast shadow?

The next step has to be seeing if the radio runs outside next to the car, power it with an extension cord - tell us what you hear.

AM or FM broadcast?

AM can be absolutely blown away by impulse noise from a huge range of sources or high power transmissions from other AM stations in very close proximity, but can penetrate into valleys etc within the coverage range of the transmitter.

FM is quite immune to impulse noise, but is very directional and literally line of sight reception. If you are in a regional area and getting regional ABC or Local ABC (Adelaide AM) from a local FM translator, the translator/transmitter will be mounted as high as practical in the area intended to be served. The radiation pattern of the transmitter would be optimised to give good coverage to the township area first, then coverage to as much of the surrounding area as possible. However because the broadcast is quite directional, if you are in a valley etc, even in visual range of the transmitter tower, you could be in a low signal area for two reasons. The first is that the transmission antenna may have been optimisised to minimise the signal being radiated down into valleys etc in order to maximise overall coverage, the second is that the signals at that broadcast band are very directional and will not bend to fill valleys or flow around hills, buildings etc to provide coverage in some areas. Both of these can place you in a broadcast shadow where reception is almost impossible because there is no broadcast signal to receive.

Trying walking around with a battery powered radio to see how it compares inside, outside house and verandah. Maybe the external antenna on the verandah was not a good location. Battery radio might help find a better signal spot for an antenna.

The aerial inside a clock radio is usually a ferite rod and very directional.
Although yiou can see the transmitter, the signal from the transmitter may be aligned in a way that means the signal in yor direction is very weak.

Try
locating the radio near a window on the side of the house facing the transmitter.
rotating the radio horizontally and vertically to see if the noise varies depending on the radio's orientation.
as already suggested, repeat this location / rotation regime outside.

My guess is that the broadcast signal in your direction is too weak to get past or through the metal shed and/or house roof.
the solution is likely to involve an external aerial mounted on the roof of the house.

I appreciate all the advise you guys have given. However it now turns out there is nothing that can be done about this crazy situation. Even ABC local radio jocks advise verbally its one of the joys of rural living on Eyre Peninsula.

Can this now be closed.

Here is my guess.

You have electricity in the shed. I assume that you also have a panel of sorts to supply the shed.

If the panel has its own ground rod, there is a ground loop. Move that ground to the ground bar in mail panel. That should solve your static problem.