APRS Local Frequency Info Initiative


Bob Bruninga, WB4APR


The local repeater frequency object shows the frequency, the tone, typical operating range and weekly net times. On the right,
you can see a 443.375+ repeater along with all the other APRS stations on the new Avmap G5 map display. click for full size
see video on AVMAP


This page addresses three topics related to the use of Local Frequency and information objects in APRS:

  • Voice Repeater Frequency Objects for the mobile traveler no matter where he goes
  • Mobile Operating Frequencies injected into mobile position reports
  • Voice Frequency Identification on every repeater and every operator. Hear on-air sample (it really only goes out after X mins between PTT's. And you would not hear it at all on a properly implemented repeater because the TNC would mute the repeater output during that 0.2 seconds.)

    VOICE REPEATER FREQUENCY OBJECTS: . For facilitating communiations (especially for first-responders, visitors and travelers), local APRS digipeaters provide locally recommended voice repeater frequencies to mobile users. . The left side of the D700 display above and the D7 screen to the right shows the local Frequency object recommended for this area. . Since Jan-07 we have been encouraging this Local Info Initiative to get not only the recommended voice repeater object on the air, but also all other RF assets of value to the traveler such as the local IRLP, EchoLink, and Winlink frequencies, or NET times or meetings in progress, etc as shown here.

    Notice how the IRLP and ECHOLINK nodes identify not only their node numbers and callsigns, but also their Tone, Range and status. (Bsy, Rdy, Lnk etc)... By pressing the OK button to see the POSIT screen, you can see that the Echolink node is 17.1 miles to the Southwest.

    APRS is a two-way local Information Distribution and Communication System
    (not just a vehicle tracking system). See APRS misconceptions!
    The objective is Human-to-human local real-time info and communications!
    .

    TRACKERS ARE TWO-WAY-TOO: . Even transmit-only APRS trackers should be configured to facilitate two-way human communications. This is done by always using a transceiver and tuning the RECEIVER to a desired voice communication calling channel. . Then placing this frequency information into the beacon text of the tracker. . This way, all who see the tracker can also establish contact with the operator. . Often this can simply be the Voice Alert frequency.

    APRS IS NOT JUST VEHICLE TRACKING: APRS was invented back in the 80's as a universal local tactical info exchange channel designed to inform all users of everything going on on Ham radio in the surrounding local area in real time via short beacon packets. Vehicle position packets were only a subset added in the 90's when GPS became plentiful. We assumed that local frequency information would appear on APRS mobile displays. . APRS is all about exchanging local info and facilitating communication between users. . Knowing the local recommended frequency is very important to travelers. . On the other hand, these radios make excellent data entry devices at special events too. (and not just position!). See D7 data entry at a scout event.

    Messaging: Don't overlook that these radios can also send and receive messages between mobiles or HT's anywhere in the world. They can even be used to send Email as shown below. . Just press the MSG button, select INPUT on the MSG Menu, enter EMAIL as the address, and make the first text of the message be an email address followed by your message. . In the example below, an EMAIL to A3XYZ@AMSAT.ORG says OK in OceanCity with HT & whip!. .

    If your email is digipeated, then you will see MY MESSAGE flashed on the screen indicating success.

    RECOMMENDED REPEATER FREQUENCEIS: . We have seen steady growth since this concept began. The latest sample on 3 April 2008 is at 255 on 2 meters. I think the 323 count in January had some errors and without that data point, the curve is a nominal growth curve. . To see the progress we are making in each band segment on this initiative, see these links:

  • 147.0xx, 147.1xx, 147.2xx, 147.3xx repeaters.
  • 146.6xx, 146.7xx, 146.8xx, 146.9xx repeaters.
  • 145.1xx, 145.2xx, 145.3xx, 145.4xx repeaters.
  • 442.xxx, 443.xxx, 444.xxx. 449.xxx UHF repeaters.
    Note: An anomoly in FINDU.COM does not display the map for frequency objects
    with a "+" in them, though the object is listed and still works fine locally on RF.

    TINY WEB PAGES: When the Kenwood D7 and D700 APRS mobiles came out in 1998 that could display this info directly on the radio front panel, we called this info Tiny-Web-Pages. See the TWP paper presented at the year 2000 DCC. . The intent was to have all local ham radio activities of immediate local interest show up on these radios to inform mobiles in real time about evertyhing going on in ham radio around them. . An APRSdata.exe program was written that could be run on someone's PC which would then transmit to the front panel of all local radios, information on everything such as WX, Satellites, DX, traffic, Nets, Meetings and so forth. But as APRSdos became less used, and follow-on APRS clones focused too much on only vehicle tracking, most users these days have not seen these other applications for pushing local information to mobiles in the area. I expect to see lots more than just tracker callsigns show up on my radio. Some examples:

    For NETS, use the "/N" NTS symbol and for meetings and HAMfests, use the "/E" EYEBALL symbol.

    THE LOCAL INFO INITIATIVE: This web page intends to highlight this new initiative to get back some of this original APRS functionality. In particular, the display of local voice repeaters to mobile travelers in new areas such as shown above. The display at the top of this page is what flashes on the front panel for 10 seconds when the packet is received. If the driver does not happen to see this display, then the Repeater will show up as an object on the radio's STATION list as shown to the right on a D700:

    In this case, the newer 146.76 repeater has appeared on the list and the older repeater from the previous town is going down the list. Of course, usually it is much further down the list than shown here. When the user sees one of these repeater objects in his STATION list he can know that he is in DIRECT range of that repeater and he can select it to see any other amplifying information such as tone, range, nets and meeting times.

    FREQUENCIES ON STATION LIST on the D710: . In the next photo to the right, the new D710 even has a column on the station list for displaying the operating frequency if it is included in the station's packet. In this case, the first three are Local Repeater Objects, but the first one of those is a cross-band repeater, so both the output frequency (object name) and input frequency can be shown. . The last two stations on the list are another D710 and D7 simply showing their current operating frequency.

    When an object is selected as shown below left, the split frequency cross band repeater example above shows on a D710 display below (complements of AB9FX). His example shows "233.6 Hz" instead of the more compact recommended "T233 RXXm" tone and range.

    . .

    The yellow D700 screen on the right above shows an example of the correct final format, though it does not use the 3rd line of 8 characters to also include the club meeting dates. Note also that TONE is now Tnnn and typical useable range is R33m in this case.

    PHILOSOPHY: It is very important for all users of APRS to understand the details and purpose of this local info system. And the most important aspect of this system is the word LOCAL, that is, the packet announcing such a voice repeater is seen DIRECT ONLY in no other area then the local DIRECT coverage area of the repeater itself. It violates the principle of this concept if these repeater objects are seen in areas where the repeater cannot be immediately worked DIRECT.

  • Done right, repeater objects are a great asset to the Traveler/Mobile APRS user with no impact on the network.
  • Done wrong, repeater objects are just more QRM and SPAM.

    FREQ SPEC: . This is all just part of the APRS Frequency Specification that encourages the addition of FREQUENCY information in all position packets of significance to improving user-to-user communications. See the AFRS Freq-Spec.

    WHICH REPEATERS: The first concept is that very few of the 10's of thousands of voice repeaters should even be considered to be announced on APRS. If more than one repeater in an area is announced, then the value of the system is diminished. We end up with nothing more than a repeater directory on the air which is displaying too-many repeaters in any given area to have any idea which one is the best for the APRS Traveler. In any given area there is usually one-and-only-one generally recommended repeater for the long haul and through traveler. That is usually the repeater with the highest probability of finding someone at all hours. ONLY those such repeaters (and/or known APRS dominated voice repeaters) should be indicated on APRS.

    KEEP IT LOCAL! The second concept is that the packet simply should only cover the same area as the useble area of the voice repeater. And the packet should be originated at an APRS digipeater so that the packet does not collide with any other packet on the air. The digipeater can hear everything on the APRS channel, and it will only originate this info packet when the channel is otherwise clear. This is why this local info can be added at no cost to the network. See the list of APRS coordianators.

    FORMATS: The New-N Paradigm includes the details on how to set up these repeater info packets as objects in the BeaconText of a New-N Paradigm DIGIPEATER. The exact format was derived after extensive discussion and testing, with the displays of the D700 and D7 and HAMhud for best appearance on the front panel. Using those recommendations, the packets will only be seen locally and there will be no digipeats and no collisions with local traffic. Only THREE settings in each digipeaeter are needed:

    BEACON EVERY 10 . . . . . . .(every 10 minutes)
    UNPROTO APN383 . . . . . . . (For a KPC-3+ version 8.3. Note, no hops!)
    BTEXT ;FFF.FFxyz*111111zDDMM.hhN/DDDMM.hhWrAAAAAAAAAABBBBBBBBBBCCCCCCCC....

  • Where ;FFF.FFxyz is the frequency, and "xyz" are optional local unique characters
  •     or     ;FFF.FF5yz for 5 KHz repeaters and "yz" is one of over 3600 unique characters A-z, 0-9
  •     or     Example "xyz"s might be -IA for Iowa, -A for Atlanta, *SD for SanDiego, etc
  •     or     The "-" is useful for minus offsets, but "+" has some issues. Maybe "*" will work. See below.
  • Where *111111z is the pseudo default null Date-Time field for the OBJECT format
  • Where DDMM.hhN/DDDMM.hhWr is the LAT/LONG and "r" symbol for a voice repeater
  • Where AAAAAAAAAA, BBBBBBBBBB, CCCCCCCC, ... are the 10x10x8 free-text fields.
  • For UIDIGI roms see N8DEU's page

    FINDU.COM Workarounds: FINDU.COM has two limitations that limits the flexibility in finding unique "xyz" discriminators for your repeater. First, FINDU.COM does not distinguish between upper and lower case, and second, it does not plot the positions of objects that use the "+" in the object name. One good character for "xyz" for (-) offset repeaters is the "-". But for + offset repeaters, using the + character will cause the repeater to not be plotted on FINDU.COM (though it does list it).

    The AAAAAAAAAABBBBBBBBBBCCCCCCCC free-text field can actually be 37 bytes long, but only the first 20 bytes are visibile on the D7 and Hamhud (without scrolling) and only the first 28 bytes are visible on the D700. . Further, when these packets first come in, they are flashed on the radio in the indicated 10x10x8 three line format. So it is best to meet these word boundaries for best display on the mobiles. The following are my recommendations for the free-text fields in descending priority order. ("_" denotes a SPACE):

    First line (10 bytes AAAAAAAAAA):

  • _T079 R45m -(Combines 79.7 Hz PL tone and Range (miles or Kilo) on the first line.
  • _t079 R45m -(the lower case letter means narrowband modulation.
  • _D234 R45m -(Combines DCS code and Range on the first line.
  • _1750 R45k -(1725 Hz tone and range in kilometers
  • _Toff R45k -(Tone is OFF (no PL or CTCSS))
  • _E45m W15m -(No tone with different ranges N/S or E/W (here, 45m east and 15m west)

    Second Line (10 bytes BBBBBBBBBB):

  • _Net Tu9PM  -(if it has regular nets worthy of note to visitors
  • _Net M 9PM  -(For one letter days)
  • _Net Tu730  -(another example assuming all nets are PM)
  • _144.875rx  -(optional if it has a non stndard RX split)

    Third Line: (8 bytes CCCCCCCC):

  • _Mg3rd W  -(for meetings on M, W or F
  • _Mg3rdTH  -(for meetings on Tu, Th and Sa or Su

    Additional text: . Following the above 28 bytes, additional text may be included for APRS clients and home stations, but it will not show up on the D7 or D700.

    RANGE INDICATION: . Range is useful for the mobile, since the D7 or D700 calculate and display the range to the object. . If the Radio says it is 35 miles away, and the text says it is good to 45, then it is quite useable. . This can be "R30k" for kilometers. . Even cardiod patterns can be specified with two ranges and directions. . We don't need to specify the TONE.tenths since they are all standardized anyway. . If it is DCS then the line would be "D456   R45m"

    POSITION AMBIGUITY: . Remember that these objects can use position ambiguity since the exact location of the repeater is not needed, only its approximate location. . One-mile ambiguity is obtained if you replace the "hh" digits of LAT/LONG with two spaces each. If you want greater 10 mile ambiguity, then also replace the unit's digit of minutes with a space too.

    IRLP and EchoLink FREQUENCY OBJECTS: . In addition to the locally recommended VOICE QSO repeaters, the IRLP and EchoLink repeaters are also highly recommended to have LOCAL objects on APRS also. Their format is somewhat similliar, but we want them to show up in the station list as IRLP-NNNN and EL-NNNNNN to clearly differentiate them from the voice repeater frequency objects. Please see the AVRS web page for the overall concept and AFRS Freq-Spec for the detail format.

    ANY STATION WITH FREQUENCY! . and finally... any station that includes his frequency in his position packet will also show up to make it easy to tune. In the photo below, the new D710 not only includes a new right hand column for FREQUENCY of each station, but also the radio has a TUNE button that will instantly tune the radio to the station's indicated frequency! Also notice the SORT button. Not only can you sort all stations by RANGE, to find out who is closest to you, but if you are looking for the local repeater frequency objects, you can sort by CALLSIGN and then all of the numeric FREQUENCY objects will show up in the top five stations on the list!

    PHG DATA: Anomolies in UIview, FINDU and Kenwood prevents the consistent display of PHG range data on objects or the use of the 3rd party format. Therefore, the best way to convey repeater range is simply the format of RXXm for a range of XX miles or of Rxxk for xx kilometers. Even offset and cardiod patterns can be specified by the maximum and minimum ranges in two directions as shown in the above examples. Below is how an object with PHG data appears on APRSdos.

    OBJECTS FROM APRS CLIENTS NOT DESIRED: This Local Info Initiative is fundamentally designed around the unique features of BEACON TEXTS in local digipeaters. In contrast, it is not generally welcome to generate these repeater objects from typical APRS home user stations. These client originated repeater objects are generally not welcome for several reasons:

  • Home generated objects are not on a reliable 10 minute rate for local info or are too infrequent to be of any value
  • Home generated objects are often transmitted multiple hops instead of DIRECT ONLY and add QRM everywhere
  • Home generated objects on the uplink have a high probability of collision with other users
  • Home generated objects also take twice the channel time for a digipeat
  • There is no limit to the ego or number of such home objects a local client can generate

    ONE-DIGI / ONE-VOICE-REPEATER: The simple rule of thumb, is that in the coverage area of each APRS digipeater, most locals can agree on which is the one-and-only most important voice repeater for that local direct area. Therefore, that digi should include that one voice repeater in it's beacon text. Done. This is all part of the New-N paradigm, but apparently many sysops didn't notice this part of the New-N paradigm settings.

    The reason for this new initiative is that I just returned (Jan 07) from an 1800 mile round trip between Maryland and Alabama, and only saw a few such voice repeaters the whole way. In fact, I spent almost all of my radio time while mobile, tuning around and trying to FIND the travelers repeaters. About the only way I ever found these repeaters was by running into another APRS user running Voice Alert. His PINGS alerted me to his simplex presence, and I could call him and ASK what was the local channel for the traveler. See Voice Alert or... (.DOC version)

    OBJECT PERMANENCE: Although these Frequency objects are unique local objects, there has always been the potential for confusion in the APRS system when local objects with common names are collected globally by the APRS-IS system. Fortunately for this application, there are no local display issues because no two repeaters would ever cover the same direct area on the same frequency. Thus on the front panel of a mobile radio or HAMHUD, only the local frequency would ever appear.

    For the global APRS-IS, however, there are three solutions as documented in the Permanent Object format included in APRS1.2:
    1) Object permanence is indicated with the unique timestamp of 111111z in the object format
    2) A repeater object can have one of 62 unique FFF.FFFyz names by choosing an unused character for "yz".
    3) A repeater object can have one of 3600 unique FFF.FFxyz names by choosing an unused "xyz".

    Note the limitations above of FINDU that cannot discriminate lower case from upper case of the letters "xyz" and also will not display frequency objects on the map that have a "+" in the name.

    LOCAL SATELLITE ALERTS:

    These radios can also display the frequency, doppler, azimuth and distance to any satellites in view if someone is running APRSdata.EXE on a PC as a local service in the region. . This program not only generates Satellite Objects on the front panel of all local Kenwood Radios, it also sends out every 10 minutes a schedule of the next 80 minutes of pass predictions. . The satellites are normal APRS objects, but the schedule is sent as a DX spot to the DX-LIST in the radios. This way, no one needs a tracking program, they will receive it live over the air on their radio front panel as shown below

    The first image shows the DX-SPOT list showing that there are three satellites UO22, AO27 and UO14 coming up in the next 80 minutes and when. . This schedule is updated every 10 minutes. . The next two screens are only transmitted when the satellite is in view. . They show the Range, Azimuth, Uplink and Downlink Frequencies, Doppler and distance to the satellite. Just perfect for aiming your handheld antenna. For more details see APRS Satellite Resources.

    The above screen shows how this data looks on the screen of the D700. . It is a little bit busier, since all of the data shows on just the one screen.

    NEW INITIATIVE IMPLEMENTATION STATUS: . At any time, you can query FINDU for the "r" symbol and see all of the existing Repeater Objects. . or check individual frequencies using the links near the top of this page. . As of April 08, there are over 330 such objects.

    NOTE. . FINDU has a problem with the "+" symbol in all such FFF.FFF+ objects and those objects will not show up on the FINDU maps, but they DO show up well in the "/r" list of repeater objects. . But since it has now been over 18 months and it has not been fixed, we now only receommend placing a "+" in the object name if it is absolutely necessary. Most repeater offsets are standard anyway.

    CONCLUSION: On long trips, no matter where you are, we hope you will see not only one of these recommended voice repeaters on your screen, but also the nearest IRLP or EchoLink node as well... This combined with APRS Voice Alert will guarantee that if there is someone nearby wanting to chat, we will find each other.

    Bob Bruninga, WB4APR

    P.S. . Oh, there is an on line repeater lookup system, but it is just like the repeater directory. So many repeaters, so little time to pick out the one that is useable by travelers...