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Configure TNC for ISS chat Room

June 3, 2001

G. Miles Mann, WF1F MAREX-NA 

How to configure your TNC for Unproto (Chat Room) Amateur Radio System
on ISS

In this article I will describe the equipment you need to operate the
ISS (International Space Station Alpha).  I will also discuss the
features supported by the PMS and cover the setup details for operating
the Unproto mode called Chat Room.   Other modes will be covered in
separate memos.

If you live in the US or southern Canada, you should have six-to-eight
opportunities a day to contact the International Space Station Alpha.
The Space Station Alpha is in a nearly circular orbit approximately 240
miles orbit above the earth.  It takes ISS approximately 93 minutes to
make one complete orbit around the world.  If you were to look at the
path of ISS on a flat map, it would look as if it was tracing a big
sign-wave across the map.  The top of ISS's sign-wave orbit is
approximately 51 degrees North latitude.  What all this means is, if you
live below 51 degrees North latitudes, then ISS will pass directly over
your house every few days.  ISS will also regularly pass within radio
range of your QTH several times a day for up to 10 minutes per pass.

To work ISS from your home, you should have at least the following
Amateur Radio equipment.  
·  2-meter radio with an output rating of 25 to 50 watts or more
· An Omni-directional antenna or small beam.  
· A short run of good quality coax (RG-213, 100 feet or less).  
· A standard 1200 baud AX.25 Packet modem (TNC). 

I use an inexpensive KPC-3 modem for all of my ISS packet connections,
most common TNC's will work.

TNC Configuration:

To operate the ISS PMS, you will need to modify some of the settings on
your TNC (aka Modem or Terminal Node Controller).  Most of the parameter
changes required for ISS will be compatible with terrestrial BBS
operations.  Using these suggested parameters will improve you're
connection rate and at the same time help reduce interference (QRM). 
Note, ARPS settings will be covered in a different memo.  This memo is
for Unproto / Chat Room and Email settings.  You do not need APRS to
work ISS Email or Unrproto (Chat Room)

Here is a partial list of parameter I commonly use for Kantronics TNC's
(KPC-3 and KPC-9612), your actual parameters may vary:

AXDELAY			10 [100 milliseconds]
RETRY			8-10
SLOT				10 [100 milliseconds]
TXDELAY			20 [200 milliseconds]
Unproto			CQ V R0ISS 

The Most important commands are:


AXDELAY	10 [100 milliseconds]
The value of  "n" is the number of 10 millisecond intervals to wait, in
addition to TXDELAY, after keying the transmitter before data is sent.  
This value is added to the TXDELAY value

Make sure your beacon is disabled.  Unattended beacons on the ISS packet
uplink will just cause interference.  You should only transmit manually
while you are at controls.  Note: during pre-arranged special events,
the ARISS team may approved beacons for a specific date and time.  The
rest of the time, if you are not standing at your radio, keeps your TNC
beacons DISABLED.

This value seems to interfere with normal ISS BBS operations.  Make sure
LFADD is turned OFF.

Set this value on to monitor all data.

This value is normally turned "OFF" for terrestrial BBS connections and
"ON" for connections to the ISS PMS.  This value will allow you to see
packets going to other stations, while you are Connected or Attempting
to Connect.  All courteous operators using ISS will keep this value ON
while operating via ISS.    

Allows monitoring of packets while not connected.

PACLEN:  	70
Lots of short packet lengths are less likely to be clobbered than a few
very long packets.  

This will allow your TNC to decode damaged packet messages.

This is a complex collision avoidance algorithm.  The SLOT and PERSIST
command should be set according to your Manual to avoid most
collisions.  The Kantronics Defaults are acceptable

(this value is not used for unproto) You do not want to set this value
too high because you may cause QRM during your initial connect.  Also,
if "RETRY" is too short, you will time-out during the one of the 4 deep
RF signal fades.  Note:  During a 10 minute pass, there will be 4 RF
polarity shifts in the signal coming from ISS. This shift is caused by
the apparent position of the antenna on ISS's in relation to your

SLOT		10 [100 milliseconds]
This is a complex collision avoidance algorithm.  The SLOT and PERSIST
command should be set according to your Manual to avoid most collisions.
The Kantronics Defaults are acceptable

With Time Stamp turned on, you will be able to log data to your disk
while you are away and track the time and duration's of the passes. 
Make sure you clock is set correctly with DAYTIME, DAYSTR and DAYTWEAK
or similar commands.  I would suggest using UTC time in your TNC.  UTC
will help you compare logs with other stations.

TXDELAY:	20 [200 milliseconds]
This command sets the transmitter key-up delay as 10*n ms. This setting
establishes the time delay between the application of push-to-talk and
the start of packet data to the transmitter. Flags / Diddle (characters
to begin packet) are sent during the delay. This command needs to be set
long enough to give your transmitter time to come to full power before
data is sent. If set too short the beginning of the packet will be
chopped off and another station will never be able to decode you.
If set too long, additional flags at the beginning (heard as a
repetitive sound) waste air time. It may be necessary to increase your
TXDELAY to allow the receiving station sufficient time to switch from
transmit back to receive to detect your signal, or when you are using an
amplifier.  The other guys TNC will hear the Flag/DIDLE characters and
will begin to listen for real data which will follow after the AXDELAY

Most radios need approximately 300 - 400 milliseconds to allow the
transmitter to switch from Receive to Transmit and come up to full
power.  Add up the values of TXDELAY and AXDELAY to find the total time
before the first actual data bit arrives at your transmitter.  If this
value is TOO short, your packet may be damaged by your transmitter which
will prevent others, including ISS from decoding your data. If you have
an external amplifier attached to your radio, then you may need to add
an extra 100 milliseconds to the TXDELAY value.

Unproto / Chat Room:
The unproto command has two parts.  The first part can be any six (6)
letters of your choice.  Most people use CQ or a grid square location. 
The second part must be the call sign of the station you wish to use as
a Digital-Repeater (DIGI).  This call sign of the ISS DIGI this week is
NOCALL. (See Memo from Miles and Bob on the TOCALL settings.)
 cq via nocall

Now with the correct parameters configured, you will be able to monitor
all of the data coming from the ISS PMS.  The packet data you see will
typically fall into one of the 6 categories listed below:

C-Connect request
D-Disconnect request 
DM-Disconnect mode 
UA-Unnumbered Acknowledge 
UI-Unconnected Information frame
I(n)-Information frame (n=0-7).

ISS TNC Settings:
Note, some of the TNC settings on the ISS packet are not set properly,
this may intermittently cause the ISS TNC to send back your packets
before your receiver has had time to fully switch to receive.  We are
working on this issue.

Key ISS TNC settings
Slot		1 [10 milliseconds]
Persist		OFF
TXD		15 [150 milliseconds]
Axdelay	0

Calling ISS:
Before you begin calling ISS on packet, make sure you are familiar with
the operations of you packet system.  Try experimenting with a local
terrestrial PBBS or connecting to a friends TNC.  Practice Email, Chat
Room and uploading short files from your disk to another station.  See
if you can Login, upload and logout in less than a minute.  Once you
have mastered this technique on a busy PBBS frequency, you will be ready
for ISS.  Most TNC programs will allow you to save packet files you have
read to your disk. You can learn a lot from perusing you old data files
of previous ISS passes.

The ISS Call sign (June , 2001)

Due to a TNC memory battery problem, the TNC on ISS has lots its primary
configuration and has defaulted to factory settings.  The call sign has
defaulted to the letters NOCALL.  When configuring your TNC unproto
command, please use the temporary ISS call sign NOCALL (note, that's the
letter Oh, not the numeral zero).  In the future the ISS crew will
reprogram the TNC to the correct call sign R0ISS, please be away of the
pending call sign change.

Choosing the right TOCALL setting

On Sun, 29 Apr 2001, Miles wrote:
Hi everyone,

Here is a Suggestion for setting up your Unproto / Chat Room TOCALL

(Check your TNC manual for the correct syntax to change your unproto

Most unproto command are in two parts, a TOCALL parameter and a call

The TOCALL parameter section can be up to 6 characters long.  The data
in the greeting section can be just about anything.  It will not affect
the reliability of the Unproto/Chat room packet. Below are 4 examples of
unproto/chat room packets. The first part is always the call sign from
the original station.  The second part is what I am calling the greeting
section or TOCALL parameter. And the last section is the call sign of
the Digipeater.

Samples from the ISS Digi:

 W3ADO-3>APRK27,NOCALL*: <<UI>>:
 VE1JH>FN66,NOCALL*: <UI>:Hi miles
 WF1F>MILES,NOCALL*: <UI>: Welcome to ISS

Here wa3ado chose APRK27, which is related to APRS
 W3ADO-3>APRK27,NOCALL*: <<UI>>:

ve1jh-brent put in his Grid square FN66
 VE1JH>FN66,NOCALL*: <UI>:Hi miles

wf1f miles put in his first name
 WF1F>MILES,NOCALL*: <UI>: Welcome to ISS

and g6lvb put in the CQ symbol

My personal suggestion, is to replace the TOCALL greeting section with
your first name or nick name.  Putting a name in you unproto packet
string is much more friendly than a software revision number or a grid

Comments from Bob Burninga:

The "greeting" that Miles is referring to is the TOCALL in the AX.25
packet protocol.  It is usually used to address your packets to a
particular group.   APRS stations address their packets to APxxxx and
APRS uses this TOCALL address as a way of filtering out packets not
addressed to them.  

Thus they, and the thousands of APRS integrated HT and mobile radios
that display packets on their front panel, will not even see you if you
use a non-CQ or other generic BEACON TOCALL.

Of course, you are welcome to use the TOCALL for any purpose as Miles
suggests, but I just wanted to clarify, that a lot of people will not
see you if you don't use some of the standard ones that APRS accepts: 
Only the beginning characters must match.  They are shown in CAPS:

CQxxxx, BEACON, ALLxxx, QSTxxx, MAILxx, APxxxx (APRS), etc.

There are many more, but I don't remember them and will have to look
them up.   There is one special case, however, used by all the Kenwood
APRS radios.  if the packet begins with a "'" character, then they use
the TOCALL for their POSITION data....

Miles suggestions are very good way to use those 6 characters more
efficiently, but I just want to point out a disadvantage if you want to
be seen by everyone...

de WB4APR@amsat.org, Bob

For more informiaqton on ISS packet, please check the tips I have posted
on the MAREX web page

Copyright 2001 Miles Mann, All Rights Reserved.  This document may be
distributed via the following means - Email (including listservers),
and World-Wide-Web.  It may not be reproduced for profit including, but
limited to, CD ROMs, books, and/or other commercial outlets without
written consent from the author.

Until we meet again

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