AFRS (Automatic Frequency Reporting System) 8 Oct 2005 ------------------------------------------------------------------------ WB4APR Ham radio's biggest advantage of thousands of frequencies is also its biggest stumbling block at rapidly and efficiently establishing communications under emergent or immediate need. We simply need a way to determine the listening frequency of the other stations around us. Fortunately, over the last decade, APRS, the Automatic Position Reporting System, provides such a single resource for displaying not only the position and other valuable resource information on each station but it has the potential to display frequency information as well. Over 30,000 stations worldwide are currently in the system and their live position/ status reports can be seen on the air on the single national APRS frequency and on the internet. Simply view any area or station via any APRS client program or via any number of APRS web pages such as the following: http://www.jfindu.net However, currently not all APRS stations include their frequency information. We need to launch an education campaign to get users to enter the frequency information into their station position packets. We will call this initiative AFRS for Automatic Frequency Reporting System. This document specifies a common method for frequency entry so that all client programs can unambiguously parse for frequency information in any packet. PRESENT RADIO COMPATIBILITY: Already there are 3 radios than can send and receive frequency information. They are the TH-D7, DM-D700 APRS radios, plus the TS-2000 with built-in internal TNC could be upgraded with firmware to make it also transmit its frequency information. FUTURE RADIO COMPATIBILITY: We will encourage all manufacturers to consider adding AFRS capability to their transceivers to also transmit their frequency of operation. BACKWARDS COMPATIBILITY: The best news is that all existing microprocessor controlled radios could be outfitted with simple (under $99) PIC processor devices that can interrogate the radios via their serial command ports and can then beacon on the national APRS frequency their AFRS beacon. This hardware currently exists in a number of small devices called APRS TRACKRES which were originally designed to parse the GPS data and transmit position info. These same PIC processor devices could just as easily query an attached radio for its operating frequency and then include that information into its beacon as well. A good example is the pocket tracker which includes its own 1/4W transmitter already tuned to the national APRS frequency. PRESENT NATIONAL VOICE ALERT FREQUENCY: APRS operators have also noted the immediate need to contact by voice a nearby mobile without aprior-knowledge of this operating frequency. For this reason, APRS has established what it calls VOICE ALERT. This system is usually for mobiles. It simple means that instead of turning their national APRS channel speaker OFF (to avoid the packet noise) that instead they simply set CTCSS 100 and leave the volume up. This means that they operate APRS normally, but at the same time are ALWAYS monitoring the national APRS channel for a voice call with PL 100 too. This makes it possible to contact such an operator at any time because you will always know his voice monitoring frequency. Read about it on: http://nwp.ampr2.net/nwaprs/VoiceAlert OTHER SYSTEMS: It should also be noted that already, the other three global internet amateur radio linked systems, IRLP, ECHOlink and WInlink also include provisions for beaconing their POSIITON and FREQUENCY data onto the national APRS systems. This way, mobiles monitoring the national APRS frequency can be aware of the position and frequency of all amateur radio assets around them anywhere in the world. APRS FREQUENCY FORMATS: ----------------------- This addition to the APRS spec adds Frequency to the parseable parameters included in an APRS position report. This recognizes that APRS is not an end in itself, but augments other Ham Radio activities operating on other frequencies. Thus, in addition to a position, course, speed or PHG, all stations have another frequency associated with their station and this should be formally included in APRS. Also, by having a parseable frequency associated with every APRS station, voice communications is greatly facilitated. Automatic QSY can be implemented and this, combined with APRS messageing and IRLP or ECHOLINK networks can lead to fully automatic end-to-end voice connectivity between APRS users anywhere on the planet with only the knowledge of a callsign. This addition is backwards compatible to all existing software because it adds the frequency information into the position comment field. The first 10 bytes and optionally a space and an additional 9 bytes are available for this purpose. Specific 10-byte formats are required for unambiguous parsing and consistent presentation on receipt. Here are the standard 10-byte formats: 1st 10-BYTES Frequency Description ---------- --------------------------------------------- FFF.FFFMHz Frequency with obvious shift FFF.FFF(-) Frequency and standard shift FFFFFF/TTT Frequency in KHz and TONE 2nd 9-BYTES Optional Description ---------- --------------------------------------------- FFF.FFF M Alternate Frequency with obvious shift FFF.FFF + Alternate Frequency and shift FFFFFFTTT Alternate Freq in KHz & TONE Examples: 14439/100 Explicit Voice Alert example 147105107 147.105 with 107 Tone -SSSS + or - Shift in KHz These formats may be used in many combinations in the first 10 or 20 bytes. Notice that the second 10 byte fields all begin with a space (9 useable bytes) for better reading of the raw packet as shown in the examples below: FFFFFF/TTT comment... one frequency FFF.FFFMHz FFF.FFF M comment... for separate TX RX FFF.FFFMHz FFFFFFTTT comment... for separate TX RX and tone The 10/10 format is for optimal display on the TH-D7 and TM-D700 and other APRS display systems that have standardized on the 10/10 or 10/10/8 heads-up displays. Examples are as follows: +------------+ +------------+ | >WB4APR-11 | | >WB4APR-11 | | FFFFFF/TTT | | FFF.FFFMHz | | FFFFFF + | | FFF.FFF M | +------------+ +------------+ OTHER FREQUENCY FORMATS: There are two more parseable locations for frequency in the APRS protocol, one is for Object names and the other is the DX Format. OBJECT NAMES: Many locations use OBJECTS with the frequency as the object name to indicate popular traveler voice repeaters or WinLINK nodes. APRS software should be able to locate these frequencies as well. The parsing rule for these object names are as follows: OBJECT NAME ----------- FFFFFFMHz Preferred FFFFFF Preferred FFF.FFF+ FFF.FFF- Notice the two preferred formats because when these objects are transferred to an attached GPS for display as waypoints, some GPS units display an error "invalid waypoint name received" and requires operator intervention to continue operation. At least this happens with all my GPS-III units. Also note, that of course, the 10 byte frequency field in a position format can also be used as the first bytes in the comment field of any OBJECT format too. DX FORMAT: APRS also decodes the DX format, and this format includes a frequency field too. This way, APRS software needs to be aware of this frequency information too. CONCLUSION: Examples of frequency use in APRS are obvious: 1) Advertising the voice frequency you are monitoring 2) Voice repeater Objects 3) IRLP and ECHOlink nodes 4) WinLINK Packet nodes 5) EOC operations 6) Long distance travelers Since the object of APRS is to facilitate rapid response local communications, everyone should include their calling frequency in their position packets to make their availability known. de WB4APR Bob Bruninga