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Suggested RX Station for MAREX-NA Mir SSTV Images





Suggested Receiving Station for MAREX-NA Mir SSTV Images.
Jan 24, 1998

by Miles Mann WF1F,
MAREX-NA (Manned Amateur Radio Experiment, North American Division)



MAREX-NA Team designed the Mir SSTV system to be as simple as possible so
that many people from around the world will be able to receive the SSTV
signals from Mir.
The system was specifically designed  with beginners and SWL stations in
mind.
A simple receiving station should be able to decode a few images a day.

Mir SSTV Transmit system:
The transmitter on the Mir SSTV system is a Kenwood TM-V7A transceiver.
This  radio supports three different transmit power levels, (5 , 10 and 45
watts).  To conserve power resources on the Station Mir, we have programmed
the radio to default to the 5 watt setting.  The SSTV system is currently
using an antenna mounted on the PRIRODA Module. The Priroda antenna is a
dual band 2-meter/70 cm antenna, similar to a car
style dual band antenna (only the 2-meter portion is available to SSTV at
this time).
The approximate gain of the antenna on 2-meters is 0 dBd.
This will produce an approximate Effective Radiated Power (ERP) of 5 watts.
This may not sound like a lot of power, but it is more than enough for most
simple ground stations.  When Mir is directly over head, there are no trees
in the way, the signal only
needs to pass through 250 miles of air and space.  Once you get the trees
and hill out of the way, a little power goes a very long distance.

Basic Receive Station:
I am going to describe a minimum basic receiving station.  The actual
number of images you decode per day will vary.  The better your antenna
system, the more images you will be able to receive per day.

The antenna and coax cable are the most important parts of your whole radio
station.
Any omni Directional antenna, with Zero gain or more will be sufficient to
receive a few
images a day.
The quality of the coax you use, will determine how much of the power from
the antenna will be lost before it gets to your receiver.  Try to stick
with short runs (100 feet or less) of high quality coax such as RG-213 and
9914.

Most 2-meter radios will work good at receiving the SSTV signal from Mir.
I have heard a few stories of people using a Rubber-Duck and a HT.  Just
about any 2-meter HT, Mobile radio or Police Scanner, connected to an
outside antenna will work for some orbit passes of Mir.

Mir

ís Orbit:
The Russian Space Station Mir is in obit approximately 200 miles above the
earth.  The Inclination of the orbit is 51 degrees, this means that MIR is
in range of Amateur stations North and South of the equator up to 51
degrees latitude.  Stations from the USA and southern Canada should not
have problems hearing MIR during a good orbit.  The Space Station typically
comes in range 8-10 times per day for up to 10 minutes per pass.  A good
computer tracking program should be used for best tracking results.

During a 10 minute pass, the SSTV system will send 1 new image every 2
minutes.  It is possible to receive up to 5 images per pass.  However the
signals of Mir may be weak when the station is low on the Horizon.  Most
zero gain Omni directional antennas will work best when the Mir station is
above the horizon between 20-45 degrees elevation.
With a zero gain station, and a Mir orbit over 40 degrees, you should be
able to get at least one good image.
With a little practice you will be able to determine which orbits will work
best for your station configuration.

Doppler:
Doppler is a speed induced frequency shift.  This frequency shift is not
much of a problem on the 2-meter band.  There are two ways to compensate
for Doppler shift with a FM receiver.
1.  Some radios have find tuning controls, which will allow you to center
the FM signal.  The Doppler from Mir will cause the frequency to drift
between 145.982 - 145.988.  Try to tune your station to stay on frequency.
Note:  Most mobile radios and HT can not make this fine tuning adjustment,
but since Doppler is only 3.3kHz drift on 2-meters, you receiver will
usually be able to compensate if you have a good signal.

2.  Bigger antenna. The stronger the signal, the better your receiver will
Capture the FM signal.
With a strong signal, your receiver will be able to compensate for Doppler
errors greater than 5.0 kHz.

Benefits to the world
The  Mir  SSTV  experiment will also generate a lot of positive interest in
school  educational  programs.  Now for the first time school children will
not  only  able  to hear the crews talking during school schedules, but the
students  will  be  able  to see some of the 720 images per day coming from
Mir.   Web pages around the world will store the best images for schools to
log  into  and view.  Many schools are expected add Amateur Radio equipment
to  the schools so the can down load and display the images live.  To date,
over 4000 images have been transmitted from Mir to Earth.

The  success  of the Mir Amateur Radio and other Russian Satellite projects
has  been  very  good  for  Amateur  Radio  and Amsat.  Over 75% of the new
Amateur  Radio  satellite  operators  started  their  operations by using a
Russian  sponsored  satellite.   Most  of  those  people began by using the
Russian  Space  Station  Mir  Personal Message System.  The Mir SSTV system
will  help  keep  the people interested in Amateur Radio Satellites and may
encourage people to join some of the many Amateur Radio Satellite clubs.



Next week,
SSTV software decoder tips.


Web Page information:
The new MAREX-NA SSTV web is under construction but is now ON line
check it out.

www.marex-na.org


SSTV in the new:
There is a good story about the MAREX-NA SSTV project on the MSNBC web.
http://www.msnbc.com/news/227580.asp

Tracking Mir

The best way to track satellites is to get access to a good satellite
tracking program.
There are numerous programs on the market, both for sale and share ware.

The best place for current satellite position date (Kepí) data is at the
CelesTrak web page http://celestrak.com/


Copyright 1999 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.
Images received from the MAREX-NA SSTV system on the Russian Space Station
Mir
are considered public domain and may be freely distributed, without prior
permission.



Miles WF1F



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