PROTOCOL.txt 7.7 APRS ON-AIR PROTOCOLS and FORMATS COPYRIGHT 1992,93,94,95,96: Amateur radio operators may freely copy and use APRS in the Amateur Radio Service. I have tried to make APRS fully capable of receiving and plotting ALL on-the-air packets whether a station is registered or not. The registration contribution only balances the headache factor, and to cover myself against un-licensed commercial exploitation. What you get for registering is the ability to interface your OWN GPS/WX/DF units and a little convenience in saving your configuration. These APRS formats are provided for use in the amateur radio service. HAMS are encouraged to apply the APRS formats in the TRANSMISSION of position, weather, and status packets. However, the author reserves the ownership of these protocols for exclusive commercial application and for all reception and plotting applications. APRS is a trademark of Bob Bruninga. Other software engineers desiring to include APRS RECEPTION in their software for sale within or outside of the amateur community will require a license from the author. Also TRANSMISSION of APRS protocols in any NON-AMATEUR commercial application or software will require a license from the author. See COMMERCL.txt APRS uses UI frames which retain all of the error detection capability of standard packets, but without acknowledgment. In APRS, collisions or lost packets are not a problem since information is redundantly transmitted (AND effeciently! due to the decaying transmission periods). UI packets are the same type that are sent by a TNC using BEACON and BText commands. NOTE, however, that the APRS UI packets are generated internally in the APRS software and the TNC BText is not used while APRS is running. APRS uses the TNC UNPROTO command to setup the path for the trans- mission of each packet. But when we refer to the UNPROTO command in APRS, we are refering to the APRS UNPROTO or OPS-UNPROTO command which then in turn issues the hardware UNPROTO commands to the TNC. TO ADDRESS: Since APRS operates in a broadcast fashion and does not use a connected protocol, the TO ADDRESS is not required. To help APRS ignore other non-APRS traffic on the channel, APRS will normally only recognize UI packets transmitted to the generic addresses of ID, CQ, QST, BEACON, MAIL, SKYWRN, GPS, DFNET, SPCL, TEST, DRILL and APRS. All other packets are ignored. You can override this filter with the CONTORLS-OTHER command. There is also a alt-SETUP-MODES-SPECIAL command which turns off all of the above acceptible TO calls and will only accept packets addressed TO: SPCL. Similarly, these stations all transmit using the UNPROTO path of SPCL via XXXX... This makes it easy for a sub-group of APRS users to operate a special event on the same frequency as other APRS users, but to not be encumbered with all of their traffic. ALso you may use the alt-S-MODES- altNet to set up a private subnet on an APRS frequency. APRS FORMATS: In the following APRS on-air formats, the abbreviations are D for degrees (or DAY), M for minutes (Both lat/long and time), h for hundredths (or Hours), N for North and W for West. The APRS symbol is identified by the character following the Longitude (shown here as a $). See SYMBOLS.TXT. There are three types of time for local, zulu and hhmmss. POSITION REPORT: The first character determines the position report format except for the FIXED format which may occur anywhere in the packet. If the posit begins with @, M or W then either APRS, MacAPRS or WinAPRS is running. If only a TNC is running, then a / indicates that there is no APRS messaging capability on line. In this case, the date-time means the time that APRS was last running. FIXED: ... !DDMM.hhN/DDDMM.hhW$comments... (See DIGIS.txt) TNC: /DDHHMM/DDMM.hhN/DDDMM.hhW$comments... (no APRS is running) MOBILE: @DDHHMM/DDMM.hhN/DDDMM.hhW$CSE/SPD/comments... DF: @DDHHMM/DDMM.hhN/DDDMM.hhW\CSE/SPD/BRG/90Q/Comments ( Q=quality) .......z............................. (indicates Zulu date-time) ......./............................. (indicates LOCAL date-time) .......h............................. (Zulu time in hhmmss) GRDSQR: [XXnnyy]comments to end of line [XXnn]comments to end of line W3AB>FM19SX:Hello there.... (Space/MScat/Grid-SQ mode) W3AB>FM19SX:]$[Hi there.... (Space/MScat with stn symbol POWER: ..........................$PHGabcd... (Power,ant/height/Gain. OMNI-DF: ..........................\DFSxbcd... (Same as PHG, but x=sig str) RTTY: APRS DE WB4APRx/011427/3859.11'07629.11($ ... This format uses only the RTTY subset of the ASCII alphabet where ',)( mean N,S,E & W, and the x is an SSID number and the $ is the APRS symbol character. The ... comment field can contain the normal APRS CSE/SPD. The callsign must be padded to six spaces. To enable parsing of this format, use alt-A. POWER-HEIGHT-GAIN: This optional field replaces the CSE/SPD fields with a report of transmitter power, antenna height-above-average-terain and their antenna gain. With this information, APRS can plot communication range circles around all stations. The following details the format to be used in the BText of a TNC dedicated as an APRS digipeater: !DDMM.mmN/DDDMM.mmW#PHG5360/WIDE...(identifying comments)... | | | | |||| |_____ makes station show up green | | | | ||||________ Omni (Direction of max gain) | | | | |||_________ Ant gain in dB | | | | ||__________ Height = log2(HAAT/10) LAT LONG | | |___________ Power = SQR(P) | |_____________ Power-Height-Gain identifier * |_______________ # is symbol for digipeater As you can see by the integers in the PHG string, there are only 10 possible values for each of these fields as follows: DIGITS 0 1 2 3 4 5 6 7 8 9 Equation ------------------------------------------------------------------- POWER 0, 1, 4, 9, 16, 25, 36, 49, 64, 81 watts SQR(P) HEIGHT 10,20,40, 80,160,320,640,1280,2560,5120 feet LOG2(H/10) GAIN 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 dB DIR 0,45,90,135,180,225,270, 315, 360, . deg (D/45) The DIRECTIVITY field offsets the PHG circle by one third in the indicated direction. This means a front to back range of 2 to 1. Most often this is used to indicate a favored direction or a null even though an OMNI antenna is at the site. Note that 0 means OMNI and 8 means 360 or a NORTH offset. THESE HIGHTS are ABOVE-AVERAGE TERRAIN! Not above ground or sea level. Your antenna may be at 1000 ft above sealevel and be on a 100 foot tower. But if you go out 10 miles in all directions and find that the average elevation is 1100 feet, then your height-above-averag-terain is ZERO!!!! OMNI-SIGNAL-STRENGTH DIRECTION FINDING REPORT: Since APRS can plot range circles around all stations, it can also localize jammers by simply plotting the overlapping signal strength contours of all stations hearing the signal. This OMNI-DF format replaces the PHG format with DFS to indicate DF Signal strength, and the transmitter power field is replaced with the relative signal from 0 to 9. The following beacon would represent a weak signal heard on an antenna with 3 dB gain at 40 feet: @141923/3859,11N/07629.23W\DFS2230/comments A report with a signal of ZERO (0), is equally SIGNIFICANT beacuse APRS uses these 0 signal reports to draw BLACK circles where the jammer is KNOWN NOT to be. These BLACK circles where the transmitter IS NOT are VERY useful, since you will get a lot more reports from stations that dont hear the jammer than reports from those that do. The black circles eliminate a lot of territority where the fox is NOT. WEATHER REPORT: APRS uses the underline symbol character for WX reports. For these, the COURSE/SPEED field is used for the WIND and the remainder of the comment line contains other weather items. See WX.TXT @DDHHMM/DDMM.hhN/DDDMM.hhW_CSE/SPDgXXXtXXXrXXXbXXXXhXXX/U2k r is in hundredths of an inch of rain in the LAST HOUR p is in hundredths of an inch of rain in the LAST 24 HOURS s is INCHES of snow in the last 24 hours b is in tenths of millibars h is percent humidity /U2k is Ultimeter 2000, /U5 is the 500 and /Dvs is Davis OBJECT POSITION: OBJECT reports are identical to POSITs except that the posit is preceeded with a fixed nine character object name and a *. OBJECT___*DDHHMM/DDMM.hhN/DDDMM.hhW$CSE/SPD/comments... ALL OTHER PACKETS: Any packet that does NOT meet any of the above formats is assumed to be just a status beacon and is placed on the LATEST list. This list is time stamped so the receiving station will know when that status or beacon was sent. @DDHHMM/comments... MESSAGE: Station to station messages use the following format, again padding the addressee call with spaces to a total of nine characters followed by a colon: W3XYZ____:one line message text......{3 (the {3 is the line counter) MSG ACK: An ACK is just a message with the letters ACK# where the # is the message line number (following the { character at the end of the line). W3XYZ____:ack3 BULLETINS: BULLETINs are simply messages to the call signs of BLN1, BLN2, ... BLN#. They will never be acked, but all APRS stations will capture and sort them onto the special BULLETINS page. Bulletins sent to BLN# will decay to very long periods but bulletins sent to BLNx will decay down to once every 15 minutes and stay at that rate. APRS QUERIES: APRS responds to several general queries: ?APRS? - All stations respond with all outgoing status, posits, OBJs and messages randomly over 2 minutes (4 on HF) ?APRS?LLLLLL,OOOOOO,RRRR - Only stations within RRRR miles of the LLLLLL Latitude and OOOOOO Longitude respond. If RRRR is less than 8 (64 on HF) then respond immediately ?WX? - All WX stations respond MYCALL...:?APRS? - Only the station MYCALL responds immediately DF REPORTS: The DF report includes a N0Q field in addition to the position, course and speed of the vehicle plus the bearing line. @DDHHMM.xxN/DDDMM.xxW\CSE/SPD/BRG/N0Q/DF report... N0Q is a Quality indicator where Q is a quality value (1-8) amd N is an optional Number of HITS indicator. If N is 0, then it means nothing. Values from 1 to 8 give an indication of the number of hits per period relative to the length of the time period. So 8 means 100% of all samples possible, got a hit. The N is not processed, but is just another indicator from the automatic DF units. By entering a 9 as the HIT indicator, you can indicate to other users that your report is manual. DIGIPEATERS, NODES, BBS's AND ALL OTHER PACKET STATIONS: Since APRS is a generalized position displaying tool, EVERY Packet TNC that is permanently on the air, and that also transmits a periodic ID beacon, should be reporting its position in that ID beacon! This way, stations monitoring can quickly see a geographical plot of the network. If you want to keep the exact location of your transmitter ambiguous, then use the GRID-SQUARE format, and your position will be ambiguous to a few miles, but stations can still see that you are on the air. If you have special formats for your BEACONS that contain variable information, then APRS is perfect for grabbing that information and making it available to users... If you have any uused aliases, set them to RELAY so others can find you.