ATV From Space? – Try CD-ATV
by Miles Mann WF1F
This is part one of many on TV in space.
ATV, has been one of my pet projects for years, however, I never found
a way to make it affordable. Or overcome some of the technical and legal
issues.
But let’s get more people and do it.
ATV basics:
Frequency issues:
ATV uses a lot of radio spectrum (Space), about 6 MHz for a VSB signal,
which is similar to normal TV [USA] format. The 435 / 70cm band for satellites
is only 3 MHz wide. So we need to form a team to start petitioning the
ITU for more room and more uplink and down link satellite bands.
In the USA we can use full fast speed TV on 440, 900, 1.2 GHz and 2.4
GHz (on Earth). In space we smaller band segments for satellite, 435 MHz
= 3 MHz, 1.2 GHz =10MHz, 2.4 GHz = 50 MHz, but it has killer 110kHz Doppler
for LEO satellites. So if we do go into space we will need to deal with
the band-width issues and Doppler
Range:
Assume you have a HT that is running 1 watt FM Voice into a Zero Gain
antenna on the 430 band. If you wanted to send a VSB ATV signal the same
distance, with the same Zero Gain antenna you would need approximately
200 watts.
The short range is caused by the large size of the radio channel, over
6 MHz for VSB format, and even more for FM-ATV. To compensate for the
large channel you need a big antenna and or a big transmitter. That’s
why TV stations run 30,000 to 50,000 watts.
In order to legally run VSB or FM ATV full speed/frame TV in space our
choices are 1.2 GHz uplink and down link on 2.4 GHz and a big antenna
with lots of power. And don’t forget cables losses on 2.4 GHz, you
start counting inches to save on coax loss.
There is another solution that is more appealing and it is called CD-ATV,
Compressed Digital Amateur Radio TeleVision. The big benefit of CD-ATV,
is it uses much less bandwidth than VSB or FM TV signals. CD-ATV at 128
kbit data rates, uses less than 150 kHz that’s over 30 times less
bandwidth than VSB TV and when you run a narrower signal, you get better
range!
In 2004 Icom loaned me some Beta hardware for their
D-Star ID-1 project. This radio runs on 1.2 GHz and will send digital
data at a 128 kbit clock rate. With these early Beta-radios, I was able
to set up a low speed audio video link using NetMeeting video conferencing
software. The proof of concept phases prove to me that it could be done
and that there was a more affordable way to put ATV on Earth and in Space.
I submitted a proposal to ARISS as a possible ISS project. Two big issues
popped up and one was that there are going to be more European Satellites
using the 1.2 GHz band. This will prevent hams from getting Down-link
access from Ham satellites on the 1.2 GHz band. The second problem was,
Icom was only making a 1.2 GHz version of the 128 kbit radio. So the only
option is to wait for Icom to make a 70cm version of this radio, so I
can resubmit the proposal again.
CDATV on ISS
Compressed Digital Amateur Radio TV
Analog Video
- Analog FM Video requires 20 MHz
- Analog FM can only be Down-Linked on 13 cm and higher bands (2400 MHz).
- Analog FM can be Up-linked on 23 cm... and higher bands (1290 MHz).
- Analog FM provides good quality Video and Audio.
CDATV
- CDATV Requires < 150 kHz RF band width (128 KBPS).
- CDATV Down linked on 70.
- FCC allows 1260-1270 for satellite uplink.
- CDATV will send a lower quality image at QCIF rates of 5-15 Frames per
second.
Digital transceiver ID-1
Ground Station Requirements
CDATV
- Antenna-U/D: 23 cm 12 dbic $200
- Amp and Preamp: optional
- Rotor System and Tower: $1000
- Radio: $1500
- Transverter: None
- Video Converter H.323: $200
- Approximate cost: less than $3000
- Doppler TX/RX: 40 kHz
Ease of use CDATV
- To receive CDATV on 23 cm, you need to compensate for a Doppler frequency
shift to 40 kHz.
Goal and Objective
- Install and easy to use CDATV system on ISS.
- Design the system for easy access to experience Amateur Radio Stations.
- Video will be in a Half-Duplex mono band mode.
- Provide live WEB Video
Available Options
- The CDATV project is not for beginners, however video can be saved on
Web pages for easy access to schools.
- ISS will need other Amateur Radio Projects specifically designed for
Beginners (2-Meter Mono-Band packet, etc.)
- Data modem supports 128-kbit which can be used for other projects.
So lets get some heads together and put ATV in space
Miles WF1F
Email: ka1rrw@<no spam>yahoo.com
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