[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

How to use Mir Digi







September 29, 1998

Miles Mann     MAREX-NA
(Manned Amateur Radio Experiment, North American Division)
WF1F @ K1UGM.MA
mann@pictel.com

Mir and Packet UnProto mode

The Mir PMS (Personal Mail System) also supports the Digital repeating mode
called  UnProto.  I am not going to get into too much detail about UnProto,
for  more  information  check  Amateur  radio hand books and back issues of
Amateur  Radio  magazine.   Basically  UnProto  is  a way of sending packet
messages  without requiring an acknowledgment from the other station.  This
mode  is  similar to RTTY in that, you can have several stations in one big
QSO  at the same time.  Set your UnProto command in your TNC, on my KAM the
syntax  is  "U  CQ V R0MIR".  Then switch to Converse mode (enter K at cmd:
prompt).   Now everything you type will be transmitted in UnProto Mode.  If
the  Mir station hears your transmission, the Mir PMS Digi will rebroadcast
your  information  with  a  range  of over a 1000 miles.   Below is a short
UnProto between a station in Massachusetts and Alabama, using the Mir Digi.
The stations were arranging to meet on Oscar 13 when the Mir pass was over.

WF1F>CQ,R0MIR*/V [04/21/93  22:22:09]: <UI>:
hi Tim can you work OSCAR 13?

N8DEU>CQ,R0MIR*/V [04/21/93  22:22:30]: <<UI>>:
Hi miles, yes what freq?

WF1F>CQ,R0MIR*/V [04/21/93  22:22:40]: <UI>:
145.895

The  UnProto mode does not guarantee you message will ever be heard, but if
the  Mir  Digi  does rebroadcast your line of text, then you can be assured
that  someone  saw  it.  The line of text you send will be repeated with an
Asterisk after it, 

“R0MIR*/”.  If you do not see the Asterisk, then Mir did
not hear your packet.  UnProto does have its drawbacks, but it is much more
efficient  to  use  on  Mir  than  the  Direct two-way connect method. Full
two-way  packet  connects  via the Mir PMS are not recommended because they
use  up too much resources and excessive “Retires”.  Before you try Unproto
on  Mir,  I  recommend that you practice on a Terrestrial Digi first before
attempting  to  use  the  Mir station for Digi-repeating. If you make a few
UnProto  calls  and  do  not  get  any echo's back from Mir, it is probably
because  UnProto is turned off or because of a collision.  Occasionally the
System  Operators may turn off Unproto (Digi = OFF) to improve the Mail Box
traffic  flow.   The  Mail  box access should always have top priority over
other  traffic. Also there is a good time and a bad time to use the UnProto
mode with Mir PMS.
Do not use UnProto when:
1. The Mir crew is operating in Voice mode.
2.   When the Mir PMS is connected to another station that is actively
sending/receiving information from the Personal Message System (PMS).  Any
Index packets going to the R0MIR-1 address.

The  only  real  safe  time to use UnProto, is when the Mir PMS is in its 2
minute  time-out  mode.  This time-out is caused when the station connected
to  the  Mir PMS is out of range and cannot log out of Mir.  No one can log
into  PMS  Mail  box  (R0MIR-1)  until  the  connected  station  times out.
Time-outs  are the best time to use UnProto.  Before using UnProto, monitor
Mir’s  down  link  to see who is using the PMS Mail box port “R0MIR-1”.  If
you  do not seen any Index packets from Mir PMS to the ground station using
to  the “R0MIR-1” port for 60 seconds, you can assume the connected station
is out of range of the Mir PMS and its “UnProto time”.
The  shorter  the  Unproto  sentence,  the  greater  your success of  a PMS
repeat.  Long sentences may get clobbered by other stations.  If you are in
the  middle  of  an Unproto QSO and you see someone connect to the PMS Mail
box  “R0MIR-1”,  you should end your Unproto QSO and let the Mail box users
have access to the PMS.

Previous Testing of Two-way Connects:
In  1993  WA2GSY  in  New  Jersey  (now  W2KQ)  and  I  WF1F in Boston made
arrangements  to test the efficiency of FULL-TWO-WAY packet connects verses
Unroto  messages.   Unfortunately  I  have  lost the original logs from the
test,  but I do clearly remember the results.  We made arrangements for the
Mir Amateur Radio station to move to a private channel for a weekend.  Then
Joe and I attempted a Full-TWO-WAY packet Digi connect via the Mir PMS on a
perfectly  clear  channel.   The  orbit  was a perfect pass, traveling from
Texas  to  Maine.   The  10  minute  pass  had good elevation.  Both of our
stations  were  similarly  equipped  and  running  high  gain antennas with
approximately  1200  watts ERP of transmit power each.  At the beginning of
the  pass,  we  sent  a  few  Unproto packets, and then Joe issued the full
two-way  connect to my station.  After the initial log-in we each sent each
other  two  simple  lines  of ASCII text and then logged out.  Now you must
remember we had a perfectly clear channel.  There were NO other stations on
frequency  because we had moved the PMS to a private channel.  There was no
interference from any ground stations.
It  required  over  4  minutes for us to exchange the 2 lines of text.  The
total  number  of  packet transmission from all three transmitters was over
200  packets.  Every packet which I sent, had to be heard and retransmitted
by  the  Mir  PMS.   The  same packet was then sent to WA2GSY and had to be
acknowledge.  The acknowledgment from WA2GSY then had to go back to Mir and
be  re-broadcast  cast  back to my TNC.  Four transmission are required for
each  original  packet.   However since my station in Boston cant hear when
Joe’s  system  in  New Jersey was transmitting, there were dozens of packet
collisions.  These  collisions  are  what  cause  the efficiency of two-way
packet  to  drop.   With  a  full-two-way  connect each packet sent must be
acknowledged.   This  causes  a  tremendous  amount  of  over  head in this
particular   satellite   configuration.   The  efficiency  of  full-two-way
connects  via  Mir  is less than 10% on a clear channel.  Now if you add in
the  normal  amount  of traffic to the Mir public channel, you can see that
full-two-way  connects  are  a  complete  waist of time.  The efficiency of
Unproto  on  the  other hand is greater than 50%.  And Unproto is more band
friendly.
The  existing design of the Kantronics KPC-9612 does not allow us to filter
out  the  difference  between  Unproto and Two-way connects its just all or
nothing.   So we need to rely on  your courteous corporation and for people
to help spread the word on the correct operating procedures.

Good luck and lets be courteous to everyone.

Remember,  Only 1 station can connect to Mir's PMS at a time, and try avoid
using UnProto when someone is actively using the PMS Mail Box.

Copyright 1998 Miles Mann, All Rights Reserved.  This document may be
freely distributed via the following means - Email (including listservers),
Usenet, and WorldWideWeb.  It may not be reproduced for profit including,
but not limited to, CD ROMs, books, and/or other commercial outlets without
prior written consent from the author.





Bob Bruninga <bruninga@nadn.navy.mil> on 09/28/98 12:15:13 PM

To:   sarex@AMSAT.Org, amsat-bb@AMSAT.Org, aprssig@tapr.org
cc:    (bcc: Miles Mann/PicTel)
Subject:  [sarex] MIR Digi




I have been told that the MIR digi is OFF now because users are still
trying to CONNECT TO EACH OTHER instead of using the much more effecient
UI frames.  STATION-to-STATION connects via MIR digi must be avoided.

Do NOT connect to anyone but the MIR BBS if you want to use it.  If you
want to esperiment with another user and no one is logged on,  Just send a
UI frame. If you see it, then your friend did also.  It is FAR more
effecient that way.

We must some how educate users to the basics of digipeater operations that
on a satellite, attempting to CONNECT to another station via the DIGI is
about the worst thing you can do.  It will rarely be successful and it may
take DOZENS of packets and dozens of ACKS just to get ONE line through.

The effeciency of a one line CONNECTION is probably TEN times worse then
sending  the SAME one line transmitted as a UI frame!

Please if you want to experiment via the UI digi on MIR, then ONLY SEND
one or two one-line UI frames DO NOT TRY TO CONNECT TO ANYONE ELSE.  If
you want to say "Hi Joe!" then send a UI packet saying "Hi Joe".

Do Not connect (2 to 10 packets ) to get an ack (2 to 10 packets), to
establish the connection so you can send "hi joe"(2 to 10 times) to get
another ack (2 to 10 times).  Thus 8 to 40 packets to send the ONE line!
This is crazy!

bob

----
Via the sarex mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe sarex" to Majordomo@amsat.org





AMSAT Top AMSAT Home