Internet Gateway: IGate
An IGate is a type of gateway APRS station. It is similar to a network router in the TCP/IP world, or to a "voting receiver" in a wide-area radio repeater network. The IGate's job is to selectively allow packets to cross between the APRS-IS and the local RF network.
An IGate will require the following capabilities:
- RF receive (and optionally send)
- Terminal Node Controller aka TNC (may be hardware or software)
- Internet access and a connection to the Internet
- A computer or processor of some sort to implement the IGate operation
IGate implementations have to conform to the standards expected by the InternetSystemAPRS-IS system.
RF --> APRS-IS
Going from RF to APRS-IS is the simpler of the two operations. The IGate station needs to successfully connect to APRS-IS which requires a rudimentary password. Packets received via RF are sent out on the APRS-IS side. IGate implementations take care of reformatting the packet for the APRS-IS.
APRS-IS --> RF
Gating to the RF side is a little trickier. The technical parts are not difficult but the limitations of the RF channel and regulatory restrictions attendant with radio transmissions make things more difficult. Many IGate implementations will only send to RF those packets destined for stations that have been recently heard on the RF side or that are in a list of designated destination stations. As an IGate operator you are responsible for the content of the packets transmitted by your station on RF, and you should coordinate with your local or regional APRS technical coordinators to ensure that an outbound RF IGate is desirable and won't actually cause problems by creating packet duplication and/or collisions.