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The lingo

An op (short for operation) is an on-air event where ham radio operators exchange APRS messages and share position reports through APRS OTA. It’s similar to a Parks on the Air or Summits on the Air activation but there are no geographic constraints.

A host announces and runs an op over RF, and confirms each chaser’s contact.

A chaser finds an op on the air and makes a contact with its host.

The OTA bot facilitates the organization and running of ops. Hosts and chasers send APRS messages to OTA. These messages can be commands to start or end an operation, or messages between hosts and chasers which are logged as contacts. The OTA bot logs all the messages and they appear on aprsota.org as they are received.

Similar to other ham radio modes and activities, a contact is a confirmed exchange of messages between two operators. Contacts are often referred to as QSOs. On voice modes like FM or SSB, a contact typically includes the confirmation of call signs, exchange of locations, and a signal report from each operator.

For APRS OTA, we leverage the capabilities of APRS to share call signs and location information. In digital modes like APRS, the operators usually can’t evaluate signal strength. Either the packet decodes or it doesn’t. So APRS OTA contacts don’t include signal strength.

Q-codes are three character shorthand for a phrase. QSO means a two way contact or conversation between stations. Invented when morse code was the most common mode for radio transmission, Q-codes make for more efficient and less error prone messaging. The OTA bot’s commands are plain-English words like HOST, DONE, and TIME. If you are familiar with Q-codes, QRV, QRT, and QRT? are accepted as shortcuts or synonyms for these commands.

How it works

A host starts an op by sending an APRS message to the OTA bot. The first word in the message is HOST (or the Q-code QRV, meaning “I am ready”, if you prefer).

The host then transmits an APRS beacon of their current location. The OTA bot will receive that beacon, and will then send a message to the host:

That’s it. The host now has an op on the air. This is equivalent to calling CQ on an HF frequency.

With an op on the air, it’s now available for other operators to find and chase.

What’s Next

Start by testing your connectivity. Then learn how to chase an op. Chasers don’t need to transmit via RF. Dive in by finding out who is on the air right now.