Appreciated.
From what I gather, its the high frequences used by the ADS (1090) whuch warrents the higher spec cable, over distances of 5m.
As for the VHF Scanning cable which I was referring to in my original post, I have bought RG58 (cheapest) but im considering scrapping that and buy a much more industrisous cable when I can afford to by the Aerial - which is likely to be the SSE BASE128 SJ which has come recommended in another thread.