Other Packets¶
Invalid Data or Test Data Packets¶
To indicate that a packet contains invalid data, or test data that does not conform to any standard APRS format, the , Data Type Identifier is used.
For example, the Mic-E unit will generate such a packet if it detects that a received GNSS sentence is not valid.
Bytes:
| Invalid Data / Test Data Format | |
|---|---|
| , | Invalid Data or Test Data |
| 1 | n |
| Example ,191146,V,4214.2466,N,07303.5181,W,417.238,114.5,091099,14.7,W/GPS FIX Invalid GPS data from a Mic-E unit. The unit has interpreted the V character in the received sentence to mean the data is invalid, and has stripped out the $GPRMC header. |
All Other PacketsPackets that do not meet any of the formats described in this document are assumed to be non-APRS beacons. Programs can decide to handle these, or ignore them, but they must be able to process them without ill effects.
APRS programs may treat such packets as APRS Status Reports. This allows APRS to accept any UI packet addressed to the typical beacon address to be captured as a status message. Typical TNC ID packets fall into this category. Once a proper Status Report (with the APRS Data Type Identifier >) has been received from a station it will not be overwritten by other non-APRS packets from that station.
Normally, HID should be OFF in all APRS TNCs.
20th century TNCs had a command called HID which enables a special "ID" packet once every 10 minutes if the TNC is used in repeater service. But this is for use on conventional packet channels for Digipeaters, and Nodes to identify their presence. In APRS, this HID function has been replaced by the much more valuable APRS POSITION packet which not only identifies the digi, but also, its type, position, elevation and range. Thus the HID is supposed to be OFF and remain off.