I-Gating Tutorial for YAAC

The basic concept of an I-gate (Internet gateway), is that it digipeats APRS packets between the local RF network and the global Internet APRS-IS backbone network, as served by the Tier 1 core servers, the Tier 2 regional servers, and uncounted site-local servers. This permits long-distance messaging between stations not within normal digipeater hop range.

Note that, as always, you are required to be licensed as an amateur radio operator in order to transmit packets to RF; as such, the APRS-IS backbone also requires that you be licensed in order to send packets to the backbone, because packets you send to the backbone may be transmitted to RF by other stations connected to the backbone. Note that the only packets forwarded from Internet to RF will be:

1. APRS text messages addressed to an RF station that this I-gate was previously forwarded to the Internet;
2. the next position report from stations sending such text messages after the text message is forwarded;
3. any additional messages explicitly filtered forward from the Internet by the filter expression on the APRS-IS port and further enabled for RF retransmission by the supplemental Tx I-gate filter.

To function as an I-gate, your station needs the following components:

• a radio covering the local APRS frequency in your area;
• a TNC (or software equivalent) to send and receive APRS frames;
• a computer to run the I-Gating software; and
• a reliable always-up Internet connection that can get you to one of the APRS-IS servers.

YAAC is capable of functioning as I-gating software, once the following steps are carried out to set it up:

1. You need to get an APRS-IS server passcode for your government-assigned callsign, so you can send packets to the APRS-IS. If you already have a passcode for other software, it will also work with YAAC (the passcode is for the APRS-IS network, not for YAAC itself). If you do not have a passcode, please e-mail YAAC's author through his website, https://www.ka2ddo.org, sending your name and amateur radio callsign, to apply for a passcode. Alternatively, if you have a valid ARRL Logbook of the World certificate, you can use that to log into SSL-enabled APRS-IS servers.
2. You need to configure your RF port in YAAC, using either the Serial_TNC port type (for hardware TNCs or integrated radio-TNCs like the Kenwood TM-D710 or TH-D72) or the AGWPE port type (for software TNCs running on your computer and connecting to your radio through a sound card and some kind of PTT trigger port). The KISS-over-TCP TNC port type and possible additional port types provided by plugins may also be suitable for this.
3. You need to configure your passcode-authenticated APRS-IS or SSL-authenticated APRS-IS (Internet) port in YAAC, specifying your passcode or certificate and enabling the port for Transmit.
4. You need to specify your beacon symbol for an I-Gate, which is typically one of the following codes (other codes exist, but YAAC does not support their modes):
   1. I& - generic I-gate (prefer using more specific and descriptive symbol)
   2. T& - full-function 2-way I-gate (RF-to-Internet and Internet-to-RF) with one-hop receive and transmit
   3. 2& - full-function 2-way I-gate (RF-to-Internet and Internet-to-RF) with two-hop receive and transmit
   4. R& - receive-only (Rx) I-gate (RF-to-Internet only)
   5. I# - simultaneous full-function 2-way I-gate and digipeater
5. You need to ensure I-gating is enabled in the directions you will support, by viewing the expert-mode Configure dialog's Transmit tab and ensuring the Allow Gating checkboxes are appropriately enabled and the maximum hop count is properly set. Note that it is possible for YAAC to function as a digipeater and receive-only (Rx) I-gate simultaneously by setting these checkboxes appropriately, although two-way (Tx) I-gates are preferred if permitted in your jurisdiction. Use of Rx-only I-gates is discouraged as it actually reduces messaging coverage by confusing nearby Tx I-gates into thinking the Rx-only I-gate can forward messages to RF stations so the Tx I-gate shouldn't to avoid local RF bandwidth wasting with duplicate transmissions.
6. If you wish to transmit additional traffic to RF that you are receiving from the Internet, first ensure that the rate at which these supplemental packets are arriving at your station will not saturate the local RF channel when added to existing RF traffic. Then specify the most restrictive supplemental Tx I-gate filter that will include the specified traffic (and no other extra traffic).

Monitoring and Controlling Your I-Gate's Operation

A special view is provided in YAAC to display the callsigns of all stations whose packets were repeated from the Internet to your local RF network. The View menu's View Tx IGated Stations choice shows every station that was gated from Internet to RF by YAAC, displaying the last time a message was forwarded and the last time a position report was forwarded for the Internet station.

You can see all the stations you are receiving over RF by using the packet source filter to trim down the stations appearing in many of the tabular views in YAAC to only RF-originated stations. The Station/Object list is probably the most convenient view for this filter mode.

If there is a station generating objectionable traffic that you do not wish to have your station forward, the blacklisting feature can be used to prevent your station from forwarding traffic (either by digipeat or I-gate) or responding to queries from selected callsign-SSID pairs.