Packet, Pactor and APRS-nodes are used for study of propagation in the different frequencybands and for contacts between the radioamateurs. The Packet-nodes often are a meeting point for radioamteurs in a certain area or with a common interest. Momentarely all Packet- Pactor- and APRS-nodes work in FM- or SSB-mode but other forms of modulation could be a possibility.
A complete list of all the repeaters and a possibility for visualisation in "Google Earth" can be found on this page.