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Marex, How 2 RX ISS SSTV part 1 10/16/05

October 16, 2005

How to be successful with the ISS Slow Scan TV (SSTV)
Imaging system 

By G. Miles Mann, WF1F MAREXMG  for the
ARISS-International Team

There are currently two projects on board the
International Space Station that will support Slow
Scan TV (SSTV).  These projects are called SuitSat and
SpaceCam.  The SuitSat project may be activated in
December 2005 and SpaceCam in 2006 (all dates are
subject to change without notice).  The goal of this
series of memos is to get the world ready to start
decoding SSTV images from Space.  If you want to get
Ready for SuitSat and SpaceCam Slow Scan TV, then now
is the time to  start getting ready.

How to Slow Scan TV from Space, Part 1.

Slow Scan TV on the International Space Station:
The ISS Slow Scan TV system will support two-way SSTV
image transmission. SSTV is a form of sending still
images via an Analog format by radio.  Amateur Radio
operators have been using SSTV since the 1950’s. 
Today there are many software applications available
that will allow you to connect your home computer to a
radio and allow you  to decode images from space. 

The Basics:
The Slow Scan TV system on the International Space
Station that I will be focusing on is called
SpaceCam1.  The SuitSat Project may be activated
first, however the functionally is very similar. The
SpaceCam1 project is a PC based application that will
be running on board the International Space Station. 
The system will be connected to an Amateur Radio
transceiver called the Kenwood D700.  This radio will
transmit on the Amateur radio 2-meter satellite band
from the ISS (The exact uplink and down link
frequencies will be posted later).  The transmission
mode will be FM (aprox 4k deviation) and will be
sending images in the Slow Scan TV format called
Robot-36.  When SpaceCam becomes operation, it will be
transmitting over 400 images per day from the
International Space Station.  The crew will load a
directory full of still images taken earlier and then
tell SpaceCam to run “Slide Show”.  SpaceCam will then
keep sending the images from the directory over and
over again.  This will allow people on earth several
chances to decode all of the images from the directory
on board the International Space Station.

The SpaceCam slide show will be configured for a
specific delay between images.  Lets assume the delay
is set for 3 minutes. The Space Station will pass
within radio range of  your house several times a day
for up to 10 minutes per pass.  During a typical
10-minute window you will have the opportunity to
receive 2-3 images per pass.

SpaceCam & Kenwood D700 System:
The Kenwood transceiver that has a built in Packet
modem. This system is located in the Service Module. 
The Kenwood model D700 supports two Amateur radio
bands: 2-meter FM (144 – 146 MHz) and the
70-centimeter FM (435 - 438 MHz).  The built-in modem
or TNC supports 1200 and 9600 baud data rates.  The
D700 is currently connected to one of the 4 Amateur
Radio antennas mounted outside of the Service Module. 
The typical power output of this system is 5, 10 or 25
watts.  The Kenwood D700 system was activated in
December 2003.  The D700 will also be the primary
radio for the SpaceCam SSTV project.  The ISS crew
will connect the D700 to a laptop computer via a
custom designed adapter module made by ARISS. The
VOX-Box will match the audio signals from the laptop
computer to the D700 radio.  The VOX-box will also
signal the radio when it is time to transmit.

What do I need at home?
To work ISS from your home, you should have at least
the following Amateur Radio equipment:
A 2-meter FM radio with an output rating of 25 to 50
An Omni-directional antenna or small beam (the higher
the gain the better). 
A short run of good quality coax (RG-213, 100 feet or
A PC running one of the common Slow Scan TV decoding
(In this memo I will not go into the details of any
one specific SSTV applications at this time.)
And that is it for radio equipment. I use an
inexpensive Laptop computer with a 233 MHz CPU and
Windows 2000.  The software I use is either CPIX by
Silicon Pixels or and engineering version of SpaceCam1
(Sorry, SpaceCam1 is not for sale).

Slow Scan TV Decoding Software
Here are just two of the many Share-Ware SSTV
applications on the market.  There may be many more.

W95SSTV by Silicon Pixels


There are also many High quality pay software
applications that offer many more features, such as
multiple windows that allow your to simultaneously
receive an image while preparing your next image that
you want to transmit.


You will need access to a computer or web to tell you
when ISS is in range of your station. The timing of
your contact is the most important part of a
successful contact with ISS. There are many tracking
programs out in the market place today. The ARISS team
does not endorse any specific tracking program. Some
programs are share-ware (STSPLUS); others cost a few
bucks. I recommend using the DOS InstantTrack, program
by AMSAT. www.amsat.org  This program is very easy to
use and works very well with older style computers
such as 80286 style PC's. The cost of most tracking
software applications is approximately $50-100.

Doppler Shift:
The ISS Space Station is traveling around the Earth at
over 17,500-mph (28,000 Kph). This great speed will
make radio signals appear to shift in frequency. This
phenomenon is called Doppler Shift. Many of us have
radios that are Channel locked. This means you cannot
make any fine tuning adjustments to your receiver or
transmitter's frequency. Most Mobile and HT radios
cannot make any frequency changes less than 5 kHz
channel steps (lets hope that radio manufacturers will
add 1 or 2 kHz channels steps in the future). This
Doppler shift will cause the ISS transmit frequency
(145.800) to look as if it is 3.5 kHz higher in
frequency when ISS is approaching your location.
Fortunately we will be using the FM mode, and this
mode does help compensate for part of the Doppler
frequency drift automatically.  If you are fortunate
enough to have a radio with the ability to make
smaller channels steps then you should take advantage
of this feature.  You will need to review the owner's
manual for your radio to learn how to program
"Odd-Splits" channel combinations and program the
following consecutive frequencies into your radios'

For 5 kHz channel step radios do not try to adjust for
Doppler.  The exact frequency for Slow Scan TV has not
been announced at this time.
( Region 2--North & South America, Region 3Asia,
Channel 1 145.800.0 RX 144.490.0 TX Voice 
Channel 2 145.800.0 RX 145.990.0 TX Packet (Worldwide)
Channel 3 145.800.0 RX 145.200.0 TX Voice (Region
1Europe, Africa)

For VOICE (Region 2North & South America, Region
3Asia, Australia)
2.5 kHz channel step radios
Channel 1 145.802.5 RX 144.487.5 TX
Channel 2 145.800.0 RX 144.490.0 TX 
Channel 3 145.797.5 RX 144.492.5 TX

For Packet 2.5 kHz channel step radios (Worldwide)
Channel 4 145.802.5 RX 145.987.5 TX
Channel 5 145.800.0 RX 145.990.0 TX 
Channel 6 145.797.5 RX 145.992.5 TX

For VOICE (Region 1Europe, Africa) 2.5 kHz channel
step radios
Channel 7 145.802.5 RX 145.197.5 TX
Channel 8 145.800.0 RX 145.200.0 TX 
Channel 9 145.797.5 RX 145.202.5 TX

Let's assume ISS is approaching your location (QTH)
and the Slow Scan TV system is active. Use channel #4
at the beginning of the pass, then when ISS is over
head, use channel #5 and when ISS passes your QTH use
channel #6. For best results, use an updated tracking
program, which displays the current Doppler shift.
This will assist you in determining when it is best to
change channels.

As you may have noticed, it is not recommended for you
to adjust your uplink frequency on 5 kHz radios. You
may have better results if you leave your receiver on
145.800 and your transmitter on 145.990.  The Doppler
shift is only at the +3.5 kHz setting for a few
seconds, then it will slowly begin to approach zero.
After 5 minutes or less, the Doppler shift will be 0
for a few seconds, and then it will begin to swing
towards -3.5 kHz.

What is Slow Scan TV:
On this web page you will find many links to  help you
learn more about Slow Scan TV


Practice Practice Practice:
If you want to be successful in sending and receiving
Slow Scan TV from ISS you must be fully proficient in
using Slow Scan TV on Earth first, before you make any
attempt to use the Slow Scan TV on ISS.

If you can not find any friend locally to test with on
2-meter, you can always try 20-meter (14.230 USB,
assuming you have license privileges and equipment). 
During most of day and night you can easily hear
people sending SSTV images on the 20-meter band.  On
HF the most common SSTV analog mode is called
Scotty-1.  Most SSTV applications support several of
the common SSTV modes.  

You can also experiment with SSTV by plugging two
computers together, PC to PC via the sound card audio

Receiving Images from Space:
The SuitSat project will only be sending an image. 
The SpaceCam project later on, will allow both
Uploading and down loading of images from ISS.  The
Schedules for SpaceCam will be posted early next year.
 For now you will just need to concentrate on
receiving SSTV images from space.

Picking A Pass:
Use your computer program to select a good pass with
high elevation angles. When ISS first appears on the
horizon, the satellite will be 1500 miles (2400 km)
away. When ISS is directly over your house, it is only
240 miles (384 km) away. 
Using your tracking program, pick a pass with a
maximum elevation of over 40 degrees. These are
typically the best passes because ISS will be closer
to your QTH. For low elevation angles, your radio
signal will have to travel along the ground, where it
will be affected by trees, buildings and hills. When
ISS is high above the trees, you will have a clear
line-of-site shot to the ISS antenna. A 1000-mile
contact on 2-meters is easy, that is if there is
nothing between you and the other station. A good pass
is only 10 minutes long. 

Receiving SuitSat:
The SuitSat Transmitter is preprogrammed to send a
series of Voice messages, Telemetry and a single SSTV
image, every 8:46.  Then the whole process then
repeats from the beginning.  This means that each
orbit over your house you will have one or two chances
to receive and decode the image from SuitSat.  You may
also want to have your tape recording device handy to
record the rest of the messages.  The exact location
of the image is approximately 6:42 seconds from the
start of the first message. 

Don’t wait to try SSTV:

As more information becomes available on the
activation dates of the project, the information will
be posted.  It is possible that SuitSat may be
activated in December 2005.  If this it true, they you
only have a few weeks to get your home station ready
to receive SSTV image from Space. So, don’t wait until
the last minute to get your home station SSTV ready.

73 Miles WF1F MAREX-MG

Until we meet again

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