Current radar coverage
SSR only - located Mount Macedon
SSR plus primary - located Gellibrand Hill (just east of ML as described earlier)
I work in this area but am not aware of whether the radar (currently rotating) on the airfield will replace Gellibrand Hill in the airfield location or if it is testing for redeployment. I must note that as currently sited this radar would have less coverage at AV than Gellibrand Hill.
Current coverage includes the gas pipeline survey aircraft which is at about 500 ft agl and goes from the NE corner of the AV zone to the SW passing about 2-3nm north of AV. This operator is primary only and occasionally fades but is fairly solid to a couple of miles SW of AV. I have passed traffic on it to JST as a possible train only to be advised it was actually an aircraft. Oh well!
I would estimate this as the lowest practical primary coverage in the area.