for my area of monitoring.
Federal - lots of fun to listen to almost daily
ATF - is a rare catch as they tend to be more of a Target Hit [no pun] than some active surv ops [of late]
USSS - everyone thinks POTUS etc, but there is much more to the USSS and yes they are active
Nextel has been Dead since being taken over by Sprint, yes similar types of applications, but many an agency
has gotten burned by the reliance on them, and many have built out robust regional networks and/or signed-onto
Regional/State TRS's in addition to leaving their own frequencies up and running.
YMMV as to what you find/hear and the best hint is, these agencies are not like listening to your local PD/FD/DPW/EMS where you
will likely have daily activity... OP-Temp varies, could be days, weeks, months before you hear something and never ever rule out Holidays and weekends.
I Have noticed on the RadioReference, Wiki there are list of Federal, ATF and Secret Service Frequencies. As anyone ever received any of them? Or are they all old frequencies or do the use Nextel or different brand of radios? I know all Systems and Frequencies have to be issuesd by the FCC, but do they really???