Chapter 11

iGate, Digipeater and Beacon Check

Linking RF and the internet, repeating local packets, and checking how your beacons get out.

An iGate links RF and APRS-IS. An RX iGate passes what it hears on the air to the internet, which is how packets from RF-only stations reach aprs.fi. A TX iGate passes internet traffic back to the air for local stations — mainly messages.

#RX iGate (RF → APRS-IS)

Turn on Settings → RX iGATE → Enable RX iGate and connect both APRS-IS and an RF interface. Every packet received on KISS, Bluetooth, BLE, AGW, USB or the Audio TNC is sent to APRS-IS with the qAR construct:

G4ABC-9>APDR16,WIDE1*,WIDE2-1,qAR,G7JJF-10:=5301.23N/00112.34W>...

Packets are not gated if their header contains TCPIP, TCPXX, NOGATE or RFONLY, or if they are third-party packets (information field beginning }). Your own packets heard back from a digipeater are not gated (they already went to APRS-IS directly), and the same packet heard again within 30 seconds — typically via another digipeater — is gated only once.

#TX iGate (APRS-IS → RF)

Turn on Settings → TX iGATE → Enable TX iGate with at least one RF interface connected. Only traffic received from APRS-IS is considered, and only when:

• Messages (if Gate messages is on): the message is addressed to a station that has been heard directly on RF within the heard window (default 30 minutes), is not addressed to you, and its sender has not itself been heard on RF in that time (if it has, the message is already on the air locally).
• Positions (if Gate positions is on): the sender is on your watch list and has been heard on RF within the heard window.
• The packet is not from you or your iGate callsign, and has no TCPXX, NOGATE or RFONLY in its header.
• No more than three packets per source station have been gated in the last 60 seconds.

Gated packets use the standard third-party format, so receiving stations can tell that they came from the internet:

G7JJF-10>APZGJJ,WIDE1-1:}M0XYZ>APRS,TCPIP,G7JJF-10*::G4ABC-9  :See you at 8{12

#iGate identification and statistics

While the RX iGate is on and APRS-IS is logged in, the app identifies the iGate on APRS-IS every 30 minutes with the iGate message from Settings. If you use a separate iGate callsign, this is a position at your QTH with the standard iGate symbol (I&) and the message as its comment; if the iGate uses your own callsign, it is a status packet instead (skipped if you have set your own status text). It is sent on APRS-IS only.

The map's station badge shows RX-iG:N and TX-iG:N — how many packets have been gated in each direction this session. Every gated packet is also shown in Debug → Comms, marked [iGATE→IS] or [iGATE→RF].

#Fill-in digipeater

With Settings → Digipeater on, the app repeats RF packets whose next hop is WIDE1-1 or your own callsign — the first hop of the usual WIDE1-1,WIDE2-1 path — filling gaps in local coverage from a car or a hilltop. A packet is repeated on the interface it was heard on, once: a second copy heard within 30 seconds (direct or via another digipeater) is not repeated again. Your own packets, internet (TCPIP) and third-party traffic are never repeated.

The path is rewritten in the standard traceable way, so others can see who repeated it:

M0ABC-9>APRS,WIDE1-1,WIDE2-1:…   →   M0ABC-9>APRS,G7JJF*,WIDE1*,WIDE2-1:…

Digipeating needs a TNC in KISS mode (Bluetooth KISS, BLE, TCP KISS, AGW, USB KISS) or the audio modem; a TNC in text mode cannot send another station's packet. Each repeated packet appears in Debug → Comms as [DIGI] and in TX History as Digi.

#Beacon check — did my beacon get out?

With Settings → Beacon check on, and both an RF interface and APRS-IS connected, position beacons are sent by RF only, and the app watches APRS-IS for the copy an iGate passes on. It reports which digipeaters repeated the beacon and which iGate gated it, for example:

Beacon reached APRS-IS via MB7UGR → iGate M0SDM (4 s)

If no copy arrives within 2 minutes the report says so. The beacon is not sent to APRS-IS directly because the servers would then drop every iGated copy as a duplicate. Your own position still appears on your map, and the server filter is extended with your callsign so the copies reach you wherever you are. With no RF interface connected, beacons go to APRS-IS as usual.

Each result is shown briefly at the bottom of the screen and listed in Menu → Logging & Tracking → Beacon Check, newest first, with a summary of how many beacons got through and the iGates that heard you most. Via a digipeater means the beacon was repeated, but only by digipeaters that do not add their callsign to the path.

Results are kept for about a week of beaconing (the last 1,000) and survive a restart. Three buttons at the top of the window use them:

• Map (coverage map) — a dot on the map at each place you sent a checked beacon: green if it reached APRS-IS, red if it did not. Drive around with Beacon Check on and the map shows where your station gets into the network and where the gaps are. Hide dots removes them.
• Clear — deletes all results, for example before mapping a new antenna.

Who heard me — above the list, the digipeaters that repeated you and the iGates that gated you in the last 7 days, most used first, with a count. Where the app knows the station's position it adds the farthest distance it heard you from: for a digipeater, beacons where it was the first hop; for an iGate, beacons it heard directly with no digipeater in between.