Ham Radio 2000/Ham Radio 2000.iso/ham2000/packet/aprs75c/meteor.txt

Text File | 1995-11-02 | 8KB | 151 lines

METEOR.TXT  ver 7.4a:        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.


METEOR SHOWER EVENTS ON TWO METERS:

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 in
alt-S-MODES-mscaT mode:

  1) Your grid square posit is placed in the TO address of your packets
     in order to get the shortest possible packet:  W3XYZ>FM19DX:^HP
  2) Your beam Heading and Power are appended as three additional chars
     as follows:  H= heading/10      : 2=10, 9=90, A=100, Z=350 etc
                  P= squareroot(P/10): 2=40, 3=90, 5=250, 9=810
  3) your digipeater path is removed
  4) A DIRECT filter is enabled (CONTROLS-FILTER-DIRECT) which ignores
     all packets heard via a digipeater.
  5) The normal APRS filter is opened up to capture OTHER packets
  6) The country is divided into four regions, and on a 15 second cycle,
     everyone in each region transmits randomly.  This significantly
     improves the chances that stations 500 to 1000 miles away will be
     LISTENING when a DX packet is being transmitted.
  7) 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%.
  8) Your TNC is placed in FULL DUPLEX mode so multiple local TNC's
     will transmit at the same time, instead of collision avoidance.
  9) 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.


DURING A METEOR SHOWER PLEASE DO THE FOLLOWING:

1) Turn off all 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.
8) Send all MS posit reports (Greater than 250 miles) to me  either
   WB4APR @ KA3RFE.MD  (currently INOP BBS!)
   [e-mail]


METEOR SCATTER NETWORK ON 6 METERS:

   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
      which can be crystaled for 6 meters
   2) The Kantronics 9612 TNC not only has both the 1200 and 9600 baud
      modems, but it also operates simultaneously on both bands, just
      like the KAM, so the 1200 baud port can operate on 145.79 for normal
      APRS activity, and the 9600 baud side can operate the 6M MScat
      channel.  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!?
   50.64
   50.66
   50.68
   50.70  OLD RTTY FREQ
   50.72
   50.74
   50.76
   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.