| Project
Name: MIREX-2 |
G.
Miles Mann, MIREX
Revision 1.0
October 8, 1997 |
This is the Mirex proposal
for the second Amateur Radio station on the New ISS. This
proposal will attempt to improve on what has proven to
work very well and add support for 9600 baud packet. This
proposal does not cover all of the exact
hardware/software details of the equipment
implementation.
| Goals: |
|
| 1 |
The
new Mirex-2 ISS-PMS will be designed to challenge
Amateur Radio stations by offering them a choice
of using 2-meters at 1200 baud, or 70cm and 9600
baud packet. |
Go! |
| 2 |
The
new ISS-PMS, receiver specification: |
Go! |
| 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
modes. |
Go! |
| 4 |
The
first new 9600 baud ISS-PMS, will support 1 users
(Multiple user support will be added at a later
time) |
Go! |
| 5 |
Limitations
and restrictions will be added to enhance message
traffic and reduce interference. |
Go! |
| 6 |
Hardware,
this design may require some custom hardware and
software development. |
Go! |
| 7 |
Mono
Band operations verses Dual Band operations. |
Go! |
| 8 |
Remote
control from authorized Amateur radio ground
control stations. |
Go! |
| 9 |
Project
Duration |
Go! |
| 10 |
Skill
Level |
Go! |
Details:
1. The new ISS-PMS will need to be
accessible by as many people around the world as
possible.
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 Mirex-2 ISS-PMS
will support 9600 baud AX.25 Packet, in the FM mono-band
mode.
Ground station
requirements will be similar to the existing Mir PMS,
including:
- Antenna 0 dBd Gain Omni
or small Yagi,
- Radio, standard FM mobile 25 watt transceiver or better
- Terminal Node Controller (TNC) supporting 9600 baud
AX.25 packet protocol
 Top
2. The new ISS-PMS, receiver
specification:
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 20k Doppler shift will be a big challenge to ground
stations.
Ground stations will need to shift their transmit
frequency during a ISS-PMS Pass.
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.
Suggested
Transceiver:
| Kenwood
TM-V7 |
| Frequency Range |
144
Mhz: |
TX:
144 - 148 Mhz
RX: 118 - 174 Mhz |
| 440 Mhz: |
TX: 430 - 450 Mhz
RX: 410 - 470 Mhz |
| Mode |
F3E (FM), A3E (AM) (VHF Main band Rx
only) |
| Power
Requirement |
13.8 V DC +/- 15 %, negative ground |
Current Drain (High Power)
Transmit |
144 Mhz: Less than 11 A
440 Mhz: Less than 10 A |
| Receive |
144/440 Mhz: Less than 1 A |
| Operating
Temperature |
-4 deg F ~ +142 deg F (-20 deg C ~
+60 deg C) |
| Antenna
Impedance |
50 Ohms |
| Microphone
Impedance |
600 Ohms |
| Frequency
Tolerance |
+/- 3 ppm (14 degF - 122 degF) |
| Weight |
1.2 kg |
| Dimensions,
projections not included (W x H x D) |
5-1/2 x 1-9/16 x 7-7/16 ins |
| |
|
| TRANMITTER |
| RF
Output Power |
HI
Mid (approx)
Low (approx) |
144 Mhz: 50W, 440
Mhz: 35W
10 W
5W |
| Modulation |
Reactance
Modulation |
| Maximum Frequency
Deviation |
Less
than +/- 5 kHz |
| Spurious
Radiation |
Less
than -60 db |
| Modulation
Distortion |
Less
than 3% (300-3000 kHz) |
| |
|
|
| RECEIVER |
| Circuitry |
Double
Conversion Superhetrodyne |
| Intermediate Frequency |
1st IF |
144 Mhz: 38.85
Mhz
440 Mhz: 45.05 Mhz |
| 2nd IF |
144 Mhz: 450 Khz
440 Mhz: 455 Khz |
| Sensitivity
(12db SINAD) |
144
Mhz: Less than 0.16 uV
440 Mhz: Less than 0.16 uV |
| Sensitivity |
-6 db
More than 12 kHz
-60db Less than 28 kHz |
| Squelch
Sensitivity |
144
Mhz: Less than 0.1 uV
440 Mhz: Less than 0.1 uV |
| Audio Output
Power |
More
than 2 W (8Ohms, 5% distortion) |
Top
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
received signal.
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
antenna solution.
Top
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.
Features of the
KPC-9612 Plus, running at 9600 baud on 70cm
Hardware
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
attached devices
Two analog inputs which can be monitored with the ANALOG
command
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
Firmware
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,
automatically
Command sets for both new and experienced users; on-line
help messages for each command
Top
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
stations.
The Digital-Repeater
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
base:
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.
Top
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
designed hardware.
Top
7. Mono Band operations verses Dual Band
operations:
To simplify operations,
the system will be used in a Single band configuration.
Top
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
telemetry
- To be defined
Top
9. Project Duration:
This project is expected
to be the second Amateur Radio Experiment enabled on the
ISS.
It is expected the 70cm 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 70cm 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 70cm 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 launch.
The long term goals for 70
cm packet for ISS, are to expand the capacity and at the
same time, not interfere with the existing beginners
2-meter Mono band project.
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.
Top
10. Skill Level
Mirex tested the 70cm band
in September 1997. We found that 75% of the existing
2-meter users of the Mir PMS, could not afford to operate
the 70cm packet on Mir.
A similar problem would occur if a PMS was designed to
operate as a dual band system (70 cm uplink with 2-meter
down link).
This project has been
designed for the more advanced users who can afford the
additional expense in operating 70cm.
Skill
Level 2: Intermediate
Newly licensed Amateur
Radio stations with Minimal technical and practical
experience.
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.
Access: Satellites
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
level 1.
Top
Summary:
| After
a ground station has mastered 2-meter 1200 baud,
they can learn how to support the challenging
70cm 9600 baud operations. 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. |
|
Mirex ISS