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Amateur Radio Emergency Service (ARES)
Berks Country Department of Emergency Services
U.S. Radio Amateur Civil Emergency Service (RACES)

Government Pages:

The FCC’s Amateur Radio Service Page
Industry Canada’s Amateur Radio Service Page

Local Clubs (to the greater southeastern Pennsylvania area):

Appalachian Amateur Radio Group (AARG)
Berks Amateur Radio Club (BARC)
Lebanon Valley Society of Radio Amateurs (LVSRA)
Mid-Atlantic Amateur Radio Club (MARC)
Mt. Airy VHF Radio Club (aka Pack Rats)
Phil-Mont Mobile Radio Club (PMRC)
Reading Radio Club
Red Rose Repeater Association
Schuylkill Amateur Repeater Asscociation
Southern Pennsylvania Amateur Radio Club (SPARC)

Organizations and Clubs:

The American Radio Relay League (ARRL)
DMR Motorola Amateur Radio Club (DMR-MARC)
Radio Amateurs of Canada (RAC)
Radio Amateur Satellite Corporation (AMSAT)
Tucson Amateur Packet Radio (Digital Communications)

Online Tools and Utilities:

Coax Cable and Line Loss Calculator
eQSL (electronic QSL card system)
RFFinder Worldwide Repeater Directory
QRZ.com (call sign lookup)

Repeater Systems:

The N3KZ (UPenn) Repeater System
The WR3IRS DMR Repeater System
The W3BXW (BEARS) Repeater System (most of this system seems to be offline)

Manufactures and Vendors:

Alinco
Comet Antenna
Diamond Antenna
DX Engineering
HAM Radio Outlet
Hustler (New-Tronics Antenna Corp.)
Icom
Jetstream
Kenwood
LDG Electronics
MFJ Enterprises
Mosley Electronics
R&L Electronics
RF Parts
SGC
Universal Radio
Yaesu