I recently came across this report on the NTIA (National Telecommunications and Information Administration) web site;
http://www.ntia.doc.gov/osmhome/reports/2006/land_mobile_DC_06_440.doc
It is an interesting look at the usage of the VHF federal band (162 - 174 MHz) in the Washington DC area. It talks about the different agencies that are using frequencies in this band and how many users there are. It also looks at the potential impact the Justice IWN trunked system will have on frequency loading in the area. Some of the report is very technical, and there are some frequencies mentioned.
Some additonal interesting reading can be found here;
http://www.ntia.doc.gov/osmhome/reports.html
