Below is a list of resources for anyone working with or interested in RF.

FCC ULS – Search the FCC Universal Licensing System.

GPS Coordinates – Find GPS coordinates of any location.

Radio ID – Register for or search for a radio ID used on numerous networked amateur radio systems.

Signal ID Wiki – Tool for identifying all sorts of digital radio modes.

Distance and Bearing – Locate the distance and heading for any two locations. Useful for beam aiming.

RTL-SDR – Excellent resource for projects and software using inexpensive software defined radios.

QRZ.com – Long standing amateur radio resource. Probably the most popular ham radio resource.

DX Heat – Real time HF spotting

SOTA watch – Summits on the Air spotting. SOTA is a group of amateur radio folks who hike up to hills and mountains attempting to contact as many stations as possible.

hamqsl.com – Excellent, long running site for detailed HF propagation information.

BatLabs – Another long running site for all kinds of information about Motorola Radio products.

Repeater Builder – This site has also been online for a long, long time. It features a ton of information on using commercial radios for repeater use.

Radio Reference – Exhaustive frequency database. If you can’t find what you’re looking for here, then try an FCC ULS search.

Sandy’s Communications – Ham friendly Motorola authorized dealer. Owned by Sandy (K7FY) and his son Jeff (N0WTF).

ADS-B Exchange – Find unfiltered ADS-B information for airborne aircraft world wide.

SCRRBA 70 cm open repeaters – The official Southern California Repeater and Remote Base Association list of open, coordinated UHF repeaters in the Southern California region.

Southern California repeater list – A more detailed listing of Southern California amateur radio repeaters, organized by county. This resource is provided by Jet Propulsion Labs Amateur Radio Club.

TASMA 2 meter repeaters – The official Two-Meter Area Spectrum Management Association listing of coordinated VHF amateur radio repeaters.