Pasadena Radio Club
The Pasadena Radio Club was founded in 1957. It meets the fourth Tuesday of every month, except December, at 
7:00 p.m. at the Walnut Center location of Kaiser Permanente, 393 E. Walnut Street, Pasadena. Click here for a map and directions. Monthly meetings often include speakers on topics of interest to hams. Anyone with an interest in ham radio is invited to join. (Several SPARC members are also members of the Pasadena club.)
Altadena Local Emergency Radio Team (ALERT)
The goal of ALERT is to facilitate radio communications throughout Altadena and surrounding communities before, during and after a community-wide crisis. ALERT members 
volunteer their radio experience and training with Community Emergency Response Team (CERT), Neighborhood Watch programs, the Altadena Sheriff’s Station, Map Your Neighborhood (MYN), Red Cross, Amateur Radio Emergency Service (ARES), Disaster Communications Service (DCS), and National Traffic System (NTS). Visit their web site for details on ALERT’s weekly Monday night net and monthly meetings.
ARRL Los Angeles Section / ARES / NTS
Our local connection to the American Radio Relay League. From the section web site: “The section is the heartbeat of the ARRL. This is where the real work is accomplished. If you have technical questions, antenna issues, interference complaints, are looking for a local club, want to volunteer for disaster communications, or have a desire to participate in the ARRL on a local level, this is where you come.” They maintain a list of ARRL-affiliated clubs.
ARES, the Amateur Radio Emergency Service, has four district groups in the county (South Pas falls within the Northeast). Monthly meetings take place at Huntington Memorial Hospital on the second Saturday of the month. ARES Activity Day is the fourth Saturday of the month in Huntington’s West Conference Room near the cafeteria.
Our LA section hosts an extensive page on the National Traffic System. Read it for information on NTS on-air nets.
Jet Propulsion Laboratory Amateur Radio Club
This club is only open to employees and contractors of JPL, but they have an excellent web site including a very comprehensive list of repeaters.
Crescenta Valley Radio Club
CVRC has two repeaters atop Mt. Thom. Members share interests in radio and service to the community. To stay up to date with the technological changes, they invite 
expert speakers to club meetings. Many members also participate in GEARS (Glendale Emergency Auxiliary Radio). They have provided communications for Glendale Memorial Hospital, Cruise Night, the Montrose Christmas Parade and other local events. A club picnic in August features a “fox hunt” for a hidden transmitter. Details about monthly club meetings and Sunday night nets are available on their web site.
Repeater Systems
PAPA System
The PAPA System is a community of 500+ radio amateurs enjoying the use of 
twenty-two (22) inter-linked repeaters, providing extensive coverage of the Southern California region and beyond. “We have reliable communications from the Mexico border to North of Santa Barbara, and from the Arizona border to maritime mobile well out into the Pacific Ocean.” PAPA hosts an excellent guide for new hams called “Smooth Operator: How to Feel Easy About Getting on the Amateur Airwaves” by Eric Fitzgerald KG6MZS. Listen live to PAPA here.
DARN
The Disaster Amateur Radio Network. DARN is a privately funded interlinked multichannel, multiband wide-area coverage repeater system that has been on the air since 1959. DARN has 10 meter, 2 meter, 440 Mhz and 1.2 Ghz repeaters as well as DMR, Echolink and IRLP capabilities. They support several emergency comm organizations in LA and Orange Counties. “We are always looking for a few new good members.” Listen to DARN live here.
WIN System
The Western Intertie System is a series of seventy-one linked, or intertied, repeaters. Most are 440 (UHF) repeaters, but they have some 2-meter and 220 repeaters as well. WIN covers a great deal of California, sixteen states, and four countries around the world. The WIN System is owned and operated by Shorty, K6JSI, with a lot of help from the faithful WIN System membership. Listen to WIN System here.
Keller Peak Repeater Association
KPR calls itself the official Inland Empire (emergency) 
communications repeater. It is on the air at 146.385 + PL. 146.2 and at IRLP node# 3216. You can listen to a live feed via Broadcastify.