i have solved this problem. the connector on the AV box is actually a male connector even though the aerial connector is also male. the thin spike of the aerial connector fits inside the hollow thicker spike of the connector on the AV Box. The solution therefore is to use a female connector (I used a female-female converter) and then you can connect a standard aerial cable. i hooked this up to my TV aerial with a UHF/VHF filter and now get very good reception. I'm amazed it took me so long to work out (brain going?). But Sony could be more explicit in their specifications. Anyway, I hope this helps someone else sometime.
