APRS Meteor Scatter

Meteors are constantly bombarding the earths atmosphere and each one leaves an ionized trail. Although there is a randomness to these events, there is enough of a continuum to provide an almost continuous data throughput of around 100 baud over ranges of 500 to 1000 miles. This is usually done by two stations operating full duplex on separate frequencies with beam antennas pointing to the same area of the sky, and running the highest practical power levels (100% transmit duty cycle). The optimum frequency seems to be around 40 MHz, making the 10 meter and 6 meter bands the most favorable. Usually data is transmitted at high data rates 4800 or 9600 baud so that the packet lengths are very short.

Can Meteor scatter work on 2 meters? Yes and no. K1HTV and W0RPK completed the first packet QSO between Maryland and Iowa during a meteor shower back in 1984. Running very high power, and it still took 2.5 hours to complete the contact. My APRS station has been on 145.79 MHz 24 hours a day for 4 years, along with hundreds of other stations across the country. In all that time I have seen only ONE packet from OHIO that could be attributed to Meteor reflection ( and it WAS during a meteor shower). HOWEVER, using APRS during the 95 Persieds, 18 stations saw packets over 1000 mile paths.

There are TWO things we can to with APRS and METEOR SCATTER. The first is to play with it on 2 meters during the very predictable Meteor SHOWERS that happen a few times a year. The second is to begin building a 6 meter MS network. APRS is an ideal tool for generating interesting but SHORT packets and for displaying and recording them.


I have implemented a MS mode in APRS to improve the probabilities of seeing APRS packets during a Meteor Shower (MS). These are all implemented using the alt-S-FORMATS-MSCATTER command:

  1. Your grid square posit is placed in the TO address of your packets in order to get the shortest possible packet:
                  |   ||
                  |   |*- - P = SqrRoot(P/10): 2=40, 3=90, 5=250, 9=910
                  |   * - - H= heading /10:    2=20, 9=90, A=100, Z=350
                  * - - - - ]$[ indicates that the TO address is the
                            grid square and that the $ is the map symbol
  2. your digipeater path is removed
  3. CONTROLS-FILTER-DIRECT is enabled to ignore all but DIRECT packets
  4. CONTROLS-OTHER is set to capture OTHER packets
  5. The country is divided into four regions and everyone in each region transmits randomly on the same 15 second sycle. This significantly improves the chances that stations 500 to 1000 miles away will be LISTENING when a DX packet is being transmitted.
  6. When your station transmits, it will send from 10 to 20 copies of your packet (.25 secs each, or about 3 seconds total). Or a full 15 seconds of packets if you choose 100%.
  7. Your TNC is placed in FULL DUPLEX mode so multiple local TNC's will transmit at the same time, instead of collision avoidance.
  8. The objective is to see POSITS and record HEARD logs. There is NO enhancement given to other APRS packets (ie, messages).
In order for this to work optimally, everyone must be synchronized to within a few seconds of WWV! APRS will let the Northeast transmit from 00 to 15, then the Southeast to 30, then the Southwest to 45 and then the Northwest to 00. The dividing lines are 39 degrees latitude and 96 degrees longitude. Most Meteor showers only peak for a few days, so, although this mode will generate a LOT of local QRM on 145.79, it wont last long!

TWO WAY CONTACTS: Two-ways are really only expected on 6 meters, but here is the procedure suggested by W0RPK and implemented in APRS72c:

  1. When you see a MS packet from another station, use the APRS SEND command to enter an Snn signal report. Send Snn where nn is the number of packets copied from that station.

  2. When you see an Snn report from another station, send back his report with an R on the end: SnnR

  3. When you see an SnnR from another station, send back SnnR73

  4. When you see SnnR73 from the other station, then you have one for the record books.

In all of these exchanges, the number nn will probably increment as the number of successfull packets accumulate. The on-air format of these packets are simply UI frames with the FROM and TO callsigns. In MScat mode, APRS automatically takes the TO call and properly places it in the packet inplace of the GRID SQUARE. TO continue with normal MScat mode, ERASE the outgoing message, and the Grid Square CQ will continue.


  1. Turn off all HF GATEWAYS!
  2. Set your UNPROTO PATH TO NONE, nothing, nadda, zip, zero
  3. Use MAXIMUM POWER and coordinate your BEAM headings not to overlap the beam headings of other transmitting stations in your area
  4. Put up with the QRM. If you need the APRS network for a special event POST A BULLETIN asking other locals to NOT TRANSMIT during your event.
  5. Be sure that at least one station in your area posts a BULLETIN advising everyone of the MS EVENT and to NOT use digipeaters.
  6. Check your screen daily for MS posits. Especially in the morning. Look at the D-LIST to be sure it was heard direct.
  7. Only the MAP, P-list and HEARD log will be useful. The L-LIST does not normally update on POSITS, and a MS packet with a GDSQ in the address, is a POSIT. It will NOT show up on the L-LIST or A-LIST.


    To make this work, we need to operate at 100 watts or more, using 9600 baud packets. This is actually quite easy to do:

    1. It is easy to find 100W surplus highway-patrol radios for about $50
    2. The Kantronics 9612 TNC has both the 1200 and 9600 baud modems that can operate on both 145.79 for normal APRS, and 9600 baud on 6m for MScat. Transmitting normal APRS packets at the normal timings, however, will almost certainly not be seen.
    3. The best way to transmit is by using any 9600 baud TNC and loading the grid square into the UNPROTO TO call, and placing the TNC into CONVERSE mode. Then periodically, a series of 10 carriage returns are sent to the TNC to force the generation of 10 minimal length position reports.
    On 6 meters, the objective of the network is still only to send and receive position reports. Remember that MS is MORE reliable than the ionosphere and HF. It will be a good band for reporting the position of distant mobiles (who can afford to run 100W on a 20% or so duty cycle!)

    THINGS TO DO! We need to get a NATIONWIDE 6 meter APRS tracking frequency AND A SEPARATE 6 meter Meteor Scatter frequency. Here is the existing band plan in the Washington DC/Baltimore area:

       50.62  Packet backbone (defunct)  XTALS in hand tho!  GOOD MS freq!?
       50.70  OLD RTTY FREQ
       50.78  SUGGESTED APRS FREQ?
       50.80  Lower band edge for remote control

    I recommend we choose a frequency FAR from the radio control OPS... I suggest 50.62 MHz, unless someone comes up with a better one.

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