Best Regional Wireless Cooperative Sites

Monitoring Scottsdale agencies on the Regional Wireless Cooperative (RWC), I seem to receive only north Scottsdale calls on the Thompson Peak site. Can anyone suggest the best sites to use that will cover all of Scottsdale? BCD396XT, ARC-XT PRO, data download from radioreference.com, discone on roof in mid-Scottsdale. Or perhaps I have missed something when setting up the system.... Thanks.