Chapter 9

Messaging

Conversations, acknowledgements, bulletins and e-mail forwarding.

APRS messaging is two-way text of up to 67 characters, with acknowledgement. The app keeps your conversations as threads, retries messages that are not acknowledged, acknowledges messages sent to you, and alerts you when one arrives.

#Messages tab

The tab has two views:

• Traffic — every message the app has overheard, including those between other stations. Messages you sent are blue on the right, messages to you are green, others are grey and labelled FROM → TO. Use Filter… to search. Flat lists messages in time order; Grouped gathers them into conversations (A ↔ B), most recently active first. Long-press to delete.
• My Messages — your conversations, one per station, newest first, with a preview of the last message and an unread count. The search box finds conversations by callsign or message text. Tap to open; long-press to delete the whole conversation.

#Starting a conversation

Tap New Message, type the callsign (with SSID if the station uses one — APRS messages go to an exact callsign-SSID) and tap Open. You can also start from Message CALL in Station Detail.

#The conversation screen

The header shows the station's callsign, distance and direction, and the interface it will be messaged on (via APRS-IS, via Bluetooth TNC and so on). ℹ opens Station Detail; the share button exports the whole thread as text. 🔔 / 🔕 mutes the station: its messages still arrive, are acknowledged and kept, but without a notification, spoken alert, tone or Android Auto read-out — for a chatty service or net. Muted conversations show 🔕 in My Messages.

Your messages are on the right, theirs on the left. Consecutive messages within 30 seconds are joined into one bubble. The status of each of your messages is shown at the start of the bubble:

Received messages show the time and ACK sent. Long-press a bubble to copy or delete it; for your own messages it also offers ℹ Delivery details — for each message (or each part), the interface it went out on, how many tries it took, when it was acknowledged and which way the acknowledgement came back. Tap a failed message (✗) — or choose ↻ Send again — to send it again without retyping; a long message's failed parts go again in order.

#Composing

• The 🎤 button lets you speak the message: the words are added to the text box so you can check them before sending (needs the phone's speech recognition, usually Google).
• One APRS message holds 67 characters. You can type more (up to 300): the counter then shows how many messages it will take (120 · 2 messages), and the text is split between words and sent in order — each part only once the one before has been acknowledged (or has given up), so they can't arrive jumbled. If a part fails, the rest are kept as failed messages to send again. The same applies to long replies from the watch, the car and notification replies. The characters {, | and ~ cannot be typed: APRS does not allow them in message text.
• Above the text box the app shows the packet that will be sent, for example G7JJF>APZGJJ,…::G4XYZ :Hello{nn. The path (…) and message number (nn) are filled in when it is sent — APRS-IS, or the RF interface the station was last heard on.
• The templates button offers saved phrases: templates saved for this station (+ Save new template, long-press to delete) and the global ones (nine built in — QRV, QRT, QSY, PSE QSL, TNX 73 and so on). {CALL}, {GRID}, {TIME} and {DEST} are replaced by your callsign, locator, the time (HHmm) and the station you are messaging. Edit global templates — or Menu → Messaging → Message Templates — adds and removes global ones.
• The position button inserts your QTH as Posn: dd.dddddN,ddd.dddddW.
• Tap the send arrow to send. Long-press it for a route override: Force APRS-IS or Force RF (every connected RF interface).

#Delivery, acknowledgement and retries

Each message is sent with a message number, :ADDRESSEE:text{N. If no acknowledgement arrives the message is sent again after 30 s, then after a further 60, 90, 120 and 150 s — six transmissions in all, over 7½ minutes — and then marked failed. An acknowledgement or a reply-ack at any point stops the retries and marks the message ✓✓. A reject (rej) marks it failed at once.

Outbox. A message sent with nothing connected is not lost: it waits in the outbox (📤) and goes out — with the usual retries — as soon as APRS-IS or an APRS radio interface connects, checked every 10 seconds. Handy when portable with patchy coverage. A conversation with a message waiting shows 📤 before its preview in the list. While anything is waiting, a 📤 Outbox row at the top of My Messages shows how many; tap it to see them all, oldest first (the order they will go), and tap one to open its conversation or delete it — or Delete all.

Reply-acks. With a station that uses APRS 1.1 reply-acks, the app uses them too: each of your messages also carries the number of that station's last message, so if your separate acknowledgement was lost, the reply confirms it. Other stations get plain message numbers, as before.

Message numbers carry on from the last one you sent, even after the app restarts, so a new message never shares a number with an old one.

Forced sends (route override) go out once, without retries. They are still marked ✓✓ when an acknowledgement arrives, and failed if none arrives within the same 7½ minutes or if no suitable interface was connected.

Receiving

• A message counts as yours if it is addressed to your callsign-SSID or to your plain callsign.
• Messages with a number are acknowledged automatically on the interface the sender was heard on.
• Reply-acks (APRS 1.1, {MM}AA) are understood: a reply carrying the number of your message acknowledges it.
• Duplicates — the same message number from the same station, usually a retry because your ack was lost — are acknowledged again but not shown, notified or forwarded twice.
• You get a high-priority notification with a Reply action so you can answer from the notification shade. Tapping the notification opens the conversation.
• Optional extras: a short beep (Message audio alert), an automatic beacon (Auto-beacon on message) and forwarding by e-mail (Email Gateway).

#Auto-reply

Settings → Alerts → Auto-reply answers messages for you — for example Driving at the moment - will reply later. 73. Choose Always, or In Android Auto to answer only while the phone is connected to the car. Each station gets at most one auto-reply an hour. The reply starts AA:, the usual sign of an automatic answer, and a message that itself starts AA: is never answered, so two stations with auto-reply on cannot keep answering each other. Service robots (JOKE, MPAD, EMAIL-2, APRS2SOTA and the like) are never answered either: only callsigns of the amateur form (a prefix, a digit and up to four letters) get a reply. Incoming messages are still acknowledged, notified and stored as usual.

#Bulletins

Bulletins are messages addressed to BLN0–BLN9 (general bulletins), BLNA–BLNZ (announcements), named groups such as BLNWX, or NWS… (US National Weather Service alerts). Menu → Bulletins lists those received over APRS-IS or RF, newest first — NWS in red, announcements in cyan. Bulletins from the last 48 hours are kept between sessions.

Every new bulletin raises a normal notification; repeats of a bulletin you already have do not. If its text contains one of your Bulletin alert keywords it raises a high-priority APRS ALERT instead.

Sending a bulletin

Tap Send on the Bulletins screen. Choose the Bulletin ID (chips for BLN0, BLN1, BLN2, BLNWX, BLNEMG, or type your own, up to five characters after BLN) and the text (up to 67 characters). The bulletin is sent on APRS-IS and on every connected RF interface with your RF path. Bulletins are not acknowledged; repeat important ones a few times over the following hour.

#Group Broadcast

Menu → Tools → Group Broadcast sends the same message individually to a list of callsigns (separated by commas or spaces). Each copy is an ordinary message with its own number, acknowledgement and retries.

#Email Gateway

Menu → Messaging → Email Gateway forwards every APRS message addressed to you to an e-mail address, so you can follow your APRS traffic from your desk. This is your own SMTP forwarding — not to be confused with the EMAIL-2 APRS service, which sends e-mail from APRS (see APRS Services).

Test checks the settings by sending a test e-mail; Send Test sends a sample forwarded message. Forwarded mail has the subject [APRS] APRS msg from CALL and contains the time, sender, your callsign, the text and optionally the position.