Medevac helicopter (Bell 220 series) accident in Aurora, IL

According to a recently released NTSB preliminary report, radar contact was not made with the helicopter for 8 miles of flight from the hospital helipad and about 5 miles later is when the accident occurred.
I was wondering at what altitude radar coverage begins (i.e. 1,000 ft either MSL or AGL), whether it is normal for helicopters to fly for miles below this altitude or whether this suggests the potential for problems - although the NTSB so far has found no mechanical failure-, etc.
A few things to keep in mind that the flight was from )LL7 (Sandwich Hospital) to 40IS (Children’s Memorial Hospital, Chicago) which is a considerable distance.

Here is a link to the NTSB report for this accident:

The NTSB report shows that this helicopter impacted an antennae at less than 700’ agl. Radar data is referenced in the report, noting that the aircraft was tracked and radar contact was lost several minutes later at a point coinciding with the accident site. This does not mean the aircraft was in contact with air traffic control, simply that after the accident the FAA was able to find a corresponding radar track. As for altitude, 700’ agl isn’t particularity low for a helicopter in cruise. Most likely scenario is the pilot was in a slow climb or elected to cruise at a relatively low altitude (perhaps this is normal local procedure to avoid conflict with surrounding airports), hadn’t yet made contact with air traffic control, and impacted an unseen obstacle.

To answer the question of radar, coverage is completely dependent on location and surrounding terrain. In most locations near major cities radar coverage is very good and goes almost to the ground. In more remote or mountainous areas you may not have radar coverage until you are 6000’ or 7000’ agl. Helicopters, including medical aircraft, operate under visual flight rules and at relatively low altitudes the vast majority of the time. In a major metropolitan area such as Chicago it is normal for helicopters to operate at lower altitudes to avoid conflicts with fixed wing traffic and expedite their own flights.

I know I speculated on several items in this post and am not questioning the pilot’s judgment or being a Monday morning quarterback, simply giving possibilities. Thoughts and prayers to all who have lost a friend or loved one.