For callsign information check out http://www.qrz.com That site has information from the FCC's database for amateur licensees and will let you search by callsign or by name or address. The callsign search box is at the top of the page, or scroll down for the name search link. US Amateurs are licensed to use frequency bands based on the class of the lecense and not just individual frequencies. For instance, the 6 meter band is 50.0 - 54.0 MHz. Information on the US amateur bands is at http://www.arrl.org/FandES/field/regulations/bands.html