NorCal APRS Regional Info

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San Francisco Bay Area

Summary Information


The San Francisco Bay Area is home to many radio amateurs and has an active APRS network. The San Francisco Bay Area terrain offers some of the best digipeater siting in the world. From almost anywhere in the central Bay Area you will have line-of-sight and clear reception to at least one high-level mountain-top digipeater. Exceptions to this are of course in areas such as the "urban canyon" of San Francisco, parts of the western side of the Coastal Range mountains from Santa Cruz north to Pescadero, the eastern side of the Diablo Range from Mt Hamilton north to Pleasanton, etc.


Due to the large number of APRS users, the 144.390 APRS frequency is almost constantly in use and efforts are always being made to reduce excessive or redundant packets. Use of "old paradigm" {paths|digipaths] (RELAY and WIDE and TRACE and TRACEn-N) is strongly discouraged and most if not all San Francisco Bay Area digipeaters will no longer respond to these paths.

Solution: Digipeater Siting Strategy

The near-ideal geographic layout of the region implies there is usually no reason for an APRS user to set up and run low-level, supplemental, or fill-in digipeaters within the central Bay Area. Doing so will almost always generate redundant packets which increases collisions and channel traffic, reducing throughput. Exceptions to this may be in urban canyons, pocket valleys, or remote areas along the coast where it can be demonstrated that a mobile station's packets do not otherwise reach the network. A special event occurring in such remote "shaded areas" may benefit from a temporary "fill-in or event" digi (which only responds to packets addressed via WIDE1-1 or it's own callsign) sited overlooking the operating area for the event duration.

If you have reason to believe that a supplemental or fill-in digipeater is needed routinely, you could join the California APRS Users Group (hosted on Yahoo Groups) and post a proposal detailing where and why. The folks there will help you determine proper settings to ensure that your digipeater is beneficial to the local users.

Solution: Receive-Only IGate Strategy

FM capture effect at Bay Area digipeaters is an issue; distance and channel congestion often results in a higher-powered station (mobile or base) covering packets from a lower-power mobile or handheld. Therefore those wishing to contribute to the local APRS system are encouraged to consider establishing receive-only IGates instead of supplemental or fill-in digipeaters. These receive-only IGates pass packets heard on RF to the Internet via APRS-IS but do not add duplicate packets to the VHF airwaves as another digi could.

Solution: Localizing Paths

Even with the "new paradigm" paths (WIDEn-N) being implemented there are still occasionally cases where local traffic will wander in or out of the Northern California region. To reduce this all digipeaters (and some stations) have started using the NCAn-N in place of WIDEn-N paths. This ensures that packets intended for Northern California users remain within the region.

Recommended path settings for mobile stations

  • WIDE1-1,WIDE2-1 : Two hops in all directions with potential to use fill-in digis. Best routine, and for events.
  • WIDE1-1,WIDE2-2 : Three hops in all directions. Not normally required; use is discouraged.
  • "Commuters" may find that a mobile path of only WIDE1-1 is adequate for their needs.
  • NCA1-1 or NCA2-2 can be used if you don't travel outside the Northern California (NCA) region.

Recommended path settings for fixed, non-moving stations

  • WIDE2-1 : One hop... suitable if you are within earshot of a "high" WIDEn-N digi with a large footprint. Avoids use of all fill-in digis.
  • WIDE2-2 : Two hops in all directions... recommended maximum for routine and courteous use in most areas.
  • WIDE3-3 : Three hops in all directions. Not normally required, use is discouraged
  • WIDE1-1,WIDE2-2 : Three hops in all directions. Not normally required, use is discouraged
  • NCA1-1 or NCA2-2 may be used. NCA1-1 is equivalent to WIDE2-1.

RELAY and WIDE and TRACE and TRACEn-N are obsolete and strongly discouraged.

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