Miles Mann MIREX Revision 1.2 Oct 8,1997
After 7 years of
continuous activity, the Mir Space Station PMS has become
the most popular Amateur Radio Satellite in the world.
When Mir is retired, a suitable replacement will need to
be found. This proposal will attempt to improve on what
has proven to work very well. And will address some of
the existing limitation of the Mir PMS system. This
proposal does not cover all of the exact
hardware/software details of the equipment
new ISS-PMS will need to be accessible by as many
people around the world as possible. Any ground
station currently capable of accessing the Mir
PMS, should continue to be able to access the
ISS-PMS with a greater success rate and with a
new ISS-PMS, receiver specification:
new ISS-PMS, should be able to take advantage of
improved antenna designs. Which should result in
stronger signals for both Transmit and Receive
first new ISS-PMS, will support 1 users (Multiple
user support will be added at a later time)
and restrictions will be added to enhance message
traffic and reduce interference.
this design may require some custom hardware and
Band operations verses Dual Band operations.
control from authorized Amateur radio ground
1. The new ISS-PMS will need to be
accessible by as many people around the world as
Any ground station
currently capable of accessing the Mir PMS, should
continue to be able to access the ISS-PMS. The
reliability of the packet link can be easily increase,
with should result in fewer bit-errors.
The Mir PMS is the easiest
and least expensive satellite in the world to operate.
The ground station requirements can be easily built or
purchased. Expanding the capabilities of the ISS-PMS,
will allow easier access and improved data through-put.
The new ISS-PMS MUST continue to support 1200 baud AX.25
Packet, in the FM mono-band mode. Ground station
requirements will be similar to the existing Mir PMS,
- Antenna 0 dBd Gain Omni
or small Yagi,
- Radio, standard FM mobile 25 watt transceiver or better
- Terminal Node Controller (TNC) supporting AX.25 packet
2. The new ISS-PMS, receiver
As most of us agree, it is
a good idea to keep the 2-meter Mono band radio station
active on Mir, and in the future on the International
Space Station. This radio will be used for both FM voice
and FM AX.25 Packet.
But the choice of the radio equipment is important, so as
not to limit access by ground stations. The 3.5k Doppler
shift is not a serious problem on 2-meters, however the
ISS radio receiver my need to be modified to accommodate
a wider receiver.
Ground stations may not need to shift their transmit
frequency during a ISS-PMS Pass. It is true that
adjusting your uplink will improve the bit-error rate on
packet, but most beginners are "Channel
A channel locked station is not able to make the fine
tuning adjustments required to compensate for Doppler.
Goals of the Ideal
1. Perform as well as the
existing Mir 2-meter station.
2. Improved Adjacent channel interference
3. Improved ability to copy off frequency stations (up to
3.5 kHz, with AFC)
4. Direct connect AX.25 Packet (volume control
5. Remote control of TNC settings from ground.
Radio -6 dB -60 dB
ICOM 228 15 kHz 30 kHz (Mir station 1993- June 1996)
Kenwood TM-733 15 kHz 28 kHz (Existing Mir Station)
Yeasu 736 12 kHz 25 kHz
Yeasu 2400 12 kHz 30 kHz
Ideal Mir 18 kHz 24 kHz (attempted Goal)
The Ideal radio should
have a wide front end at the -6dB Selectivity points.
This will allow the radio to better receive the incoming
signals when the signal is shifted 3.5k by Doppler.
Ground Station Transmits on: 145.550.0
Doppler Shift induced 3.5k (Mir heading Towards the Ground Station)
Frequency heard at Mir 145.553.5
With the old Icom radio,
less than 20% of the signal would fall out side of the
-6dB receiver Selectivity point.
With the Ideal radio, less than 1% of the signal would
fall out side of the -6dB receiver Selectivity point.
At the same time we need
to widen the -6dB point, and tighten the -60dB point to
help reduce Adjacent channel interference. With this
filter configuration, the ISS station would be in better
position to tolerate stations operating 20kHz on either
side of the ISS channel. However, I would still recommend
that all ground stations to stay at least 25 kHz from ISS
Uplink/down link frequencies.
If we use existing off the
shelf radio equipment, we should be able to meet most of
the goals. The receiver modifications could be done with
a minimal expense.
144 - 148 Mhz
RX: 118 - 174 Mhz
||TX: 430 - 450 Mhz
RX: 410 - 470 Mhz
||F3E (FM), A3E (AM) (VHF Main band Rx
||13.8 V DC +/- 15 %, negative ground
|Current Drain (High Power)
|144 Mhz: Less than 11 A
440 Mhz: Less than 10 A
||144/440 Mhz: Less than 1 A
||-4 deg F ~ +142 deg F (-20 deg C ~
+60 deg C)
||+/- 3 ppm (14 degF - 122 degF)
projections not included (W x H x D)
||5-1/2 x 1-9/16 x 7-7/16 ins
|144 Mhz: 50W, 440
than +/- 5 kHz
than -60 db
than 3% (300-3000 kHz)
||144 Mhz: 38.85
440 Mhz: 45.05 Mhz
||144 Mhz: 450 Khz
440 Mhz: 455 Khz
Mhz: Less than 0.16 uV
440 Mhz: Less than 0.16 uV
More than 12 kHz
-60db Less than 28 kHz
Mhz: Less than 0.1 uV
440 Mhz: Less than 0.1 uV
than 2 W (8Ohms, 5% distortion)
3. The new ISS-PMS, should be able to
take advantage of improved antenna designs.
Which should result in
stronger signals for both Transmit and Receive.
The existing Mir station
is using an externally mounted dual band antenna. The
gain values are unknown.
The transmitter on Mir is running approximately 5-25
watts. The current power levels on Mir have proven to be
sufficient for most ground stations. There are however
deep signals fades caused by polarity shifts in the
A new circular polarized mono band antenna should be
installed on the ISS. The circular polarization should
help ground stations running linear polarized antennas by
reducing signal fading.
An antenna on the ISS, with a gain figure of 3-9 dBic
should be possible.
The Antenna will then be place on the Nadir (Earth
facing) side of the Space Station.
At the present time MIREX
does not have the resources to provide an antenna
solution. The MAREX team will need to find a stable
4. The new ISS-PMS, should be able to
support multiple users.
The first release of this
PMS will only support 1 user. The multi user version will
not be read until late 1999.
There are existing Pac-Sats in use, which have proven the
ability of a Pac-sat to support multiple users.
The big difference with the ISS-PMS and the Pac-sats,
will be the mode (FM) and the frequency.
To keep the costs low for
ground station operators, the ISS-PMS MUST stay a
Mono-band system, in the 2-meter band. The initial system
will be able to support 1 users.
Features of the
128K byte RAM (expandable to 512K), battery
backed to save all parameters and PBBS messages
Real-time, battery-backed clock
Low power: 5.5-25 Vdc at <45 mA
Four digital output lines enable remote control of
Two analog inputs which can be monitored with the ANALOG
Eight front panel LEDs provide operational information
Measures only 0.8" x 6.7" x 6.9" (2 cm x
17 cm x 17.5 cm)
Weighs only 18 oz (0.5 kg)
RS-232 serial port (cable not included)
Expansion header allows connection of future modems
(third port) or other additional hardware
1200 Baud Port
Connects to mic jack
Internal, external, or software carrier detect
AFSK output (1mV-4V P-P) adjustable from the keyboard
with digital potentiometer
Can be configured for 300, 400, 600, or 1200 baud
9600 Baud Port
Connects to high-speed-capable radio
Can be configured for 4800, 9600, 19200 or 38400 baud and
is G3RUH compatible
Internal or external carrier detect
GMSK output (2mV-4V P-P) adjustable from the keyboard
with digital internal potentiometer
Change all KPC-9612 Plus parameters from another
packet station using remote sysop access
Can connect to one radio and still operate at two speeds,
Command sets for both new and experienced users; on-line
help messages for each command
5. Limitations and restrictions will be
added to enhance message traffic and reduce interference.
The new ISS-PMS will have
most features commonly available to terrestrial PMS
users. One specific feature the PMS will need is an
Idle-User-Timer. This timer will force a user off the
ISS-PMS, after a sysop-selectable time has expired (the
initial value of 2 minutes is suggested).
This is a limitation we
have with the current Mir PMS system. Idle-User-Timer is
hard coded into the TNC for 7 minutes and cannot be
changed by the Mir crew. This limitation has proven to be
a serious problem. When a connected ground station goes
out of range, the new stations coming in range cannot log
into Mir for 7 more minutes. This waist valuable time and
causes lots of frustration to the calling ground
option will be tuned off. All Unproto, APRS and Two-way
connects will be blocked from this ISS-PMS. We have seen
from the past 7 years of using the Digital-Repeater
option on Mir, that excessive Unproto traffic lowers the
message traffic and reduces reliability significantly. If
there is a need to Unproto and APRS traffic, then a
separate Digital-Repeater could be installed using
different frequencies on a different band.
Call Sign Date
This option could be used to assist in blocking
illegal Amateur Radio Calls. In the USA, we have several
stations using the call sign "NOCALL". The
ISS-PMS can then automatically reject illegal call signs.
An extended data base look-up table, could offer even
more protection from illegal use of the ISS BBS.
6. Hardware, this design may require some
custom hardware and software development.
It may be possible to
build this system by using off the shelf equipment.
Further investigation is needed to determine the exact
amount and weight of the ISS-PMS.
The incorporation of an AFC circuit may nessicate custom
7. Mono Band operations verses Dual Band
The two-meter band is
ideally suited for the satellite operation for beginners.
The equipment for the two-meter band is easy to build and
or inexpensive to purchase. Most new Amateur Radio
Stations first radio is a two-meter FM transceiver. This
make the two-meter band the primary candidate to
introduce new users to satellites.
The Two-meter packet band
is not plagued with the problems of the 70 cm band,
packet or voice.
The Doppler shift on two-meter band is somewhat
negligible, and station power necessary to provide
reliable communication is easily available.
The equipment and procedures are not so highly technical,
but just a solid understanding of all the fundamentals of
satellite communications is necessary.
The two meter band has the fastest growing user base of
any of the amateur radio bands in the world.
Almost all newly licensed USA technicians without code
will start with the two meter band (voice) and then add
two meter packet. This large growing base of users, will
undoubtedly lead new users to the better, but much more
highly advanced and expensive forms of satellite
This in turn should bring a wide new influx of abilities
and ideas into satellite communications leading to
development of cheaper, better equipment and methods.
8. Remote control from authorized Amateur
radio ground control stations.
Authorized Amateur radio
station on the ground should be able to remotely control
the following functions:
- All TNC Parameters
- PL Tones
- Down Load system
- To be defined
9. Project Duration:
This project is expect to
be the first Amateur Radio Experiment enabled on the ISS.
The First experiment must always be the experiment which
reaches the most users around the world. It is expected
the single user PMS system, will be in use from 1998
until the year 2000. After this date, the Multiple user
PMS should have built and ready to fly.
The proposed 2-meter Mono
band Packet system does have limited functionality in
that the initial version will only support 1 packet user.
Plans are currently in development to expand the
capabilities of the PMS system to support multiple users
via multiple 2-meter channels.
The hardware for the Multiple user system has not been
funded and as a result Mirex will only be able to fund a
single user PMS system in time for the first module
The long term goals for
2-meter packet for ISS, are to keep a 2-meter Mono band
project in place for beginners around the world for the
next 10 years.
Mirex encourages other
more sophisticated experiments to be installed on ISS,
just as long as they do not interfere with the operations
of the beginners 2-meter mono band PMS station.
10. Skill Level
Mirex has designed this
experiment for Amateur Radio Stations with a Skill level
Level 1: Entry Level
Newly licensed Amateur
Radio stations with Minimal technical and practical
Stations who have never
operated through Amateur Radio Satellites.
Limited funds: Since these
are beginners, the amount of time and money invested into
the Amateur Radio hobby is limited, their ability to work
sophisticated satellites is limited.
designed for Skill Level 1, will have the greatest access
to the largest number of stations around the world. Even
stations in Third-World-Countries should not have
difficulty in operating satellites designed for Skill
one of the goals of having an Amateur Radio on
the ISS, is to encourage greater interest in
Radio and Space exploration. Then this type of
PMS will contribute to those goals and give
people around the world a "stepping stone to
the stars". Amateur radio stations around
the world will have easier and more reliable
access to a world resource.