Gold Medal Software 3/Gold Medal Software - Volume 3 (Gold Medal) (1994).iso/misc/hod003.arj/FILE7.003

Text File | 1994-03-26 | 16KB | 297 lines

     AN INTRODUCTION TO AMATEUR SATELLITES AND EARTH-SPACE COMMUNICATIONS

The following text was compiled from the following sources:

* "How to use the EZSATS pas tables by N9LTD" reprinted without permission.
Full text, tables, and lots of other useful information can be obtained by
sending a SASE to David Mullenix N9LTD, 2052 Brentwood Pky, Madison, WI
53704

* "Amateur Radio Satellite Frequencies"  This file can be obtained from the
ARRL e-mail server.  For information on the server, send an e-mail message
to [e-mail] with 'HELP' in body of message.

* "Summary - Getting onto the Hamsats"  This was an article posted to
rec.radio.amateur.misc newsgroup by Stephan Greene
([e-mail]) on 20 Mar 1992.  The article is also available
via anon ftp from ftp.cs.buffalo.edu or Australian mirror at
grivel.une.edu.au as file pub/hamradio/ham_sat_sum.

* "An Amateur Satellite Operation Upgrade Path" from the AMSAT Journal,
September/October 1993, pp. 24-26.

FORWARD:

Having recently started to get into Satellites, I asked MANY people what
it took to get started and what to do.  I found few people who could offer
all the information necessary to start.  I have attempted to compile this
information for future newbies.  If I have missed something, please ask and
I will attempt to add it to the collection.

Also, if you really want to get serious about satellites, I would STRONGLY
recommend joining AMSAT to help promote the satellite hobby.  AMSAT is a
volunteer organization that works for the interests of amateur satellites.
Dues are only US $30 per year and you will receive a subscription to "The
AMSAT Journal".  For US $80, you will receive first year dues and a copy
of Instant Track computer tracking software which is a top-notch program.
Instant Track was donated to AMSAT by its author and its sales account for
a considerable portion of AMSAT's income.  AMSAT-NA, 850 Sligo Avenue,
Silver Spring, MD 20910-4703.  [phone].  Credit cards welcome.
NOTE:  I am in no way connected with AMSAT-NA, other than I have found their
publications quite useful.

MODES:

The combination of uplink freq, downlink freq, and transmission mode are all
lumped together into standardized satellite MODES.  Here is a list of common
satellite modes used by satellites covered by this article:

A - This mode requires a 2 meter SSB/CW transmitter and a 10 meter SSB/CW
receiver and supports CW and voice.

B - This mode requires a 70 cm SSB/CW transmitter and a 2 meter SSB/CW
receiver and supports CW and voice.  Some satellites also support RTTY
and SSTV in this mode.

K - This mode requires a 15 meter SSB/CW transmitter and a 10 meter SSB/CW
receiver and supports CW and voice.  This mode is unique in that it can
be done with a simple HF rig.

JA- This mode stands for J Analog and requires a 2 meter SSB/CW transmitter
and a 70 cm SSB/CW receiver and supports CW, voice.

JD- This mode stands for J Digital and requires a 2 meter FM transmitter and
and a 70 cm SSB/CW receiver and supports packet.

S - This mode requires a 70 cm SSB/CW transmitter and a 2.4 GHz SSB/CW
receiver and supports CW and voice.  Many people use a 2.4 GHz to 2 meter
converter with a 2 meter SSB/CW receiver instead of buying a 2.4 GHz
SSB/CW receiver.

Also, satellites have 3 basic types of retransmissions:  beacon, transponder,
and repeater.

Beacon - Most satellites have a fixed Morse beacon at the lower end of the
satellites band-pass transponder.  This is useful to detect when the
satellite has crossed the horizon and is in range for operation.  It can
also be used to determine doppler shifts.

Transponder - A transponder is a band-pass repeater.  It accepts a range of
frequencies on the input and retransmits the entire range on the output.
All offsets within that range are preserved.  NOTE:  since the satellite is
transmitting many signals at the same time, it is dividing its output power
amongst all of these signals.  If someone transmits a very powerful signal
into the satellite, it will spend most of its power retransmitting that
signal and all of the other signals will drop in power.  This is NOT a way
to earn friends and people who overpower the satellites input are called
"alligators" and are not very popular.

Repeater - This closely resembles a land-based repeater.  It listens for
signals on one frequency and retransmits it on another frequency.  All
satellite repeaters (and transponders) are full duplex, meaning you can
(and should) listen to your signal on the downlink (with headphones) while
you are transmitting.

SATELLITES:

Some satellites are easier to work than others.  The satellites that follow
can be operated fairly easily and are referred to by some as the Easy Sats.
What follows is a brief description of each satellite.  A summary list of
operating frequencies is included later.

Mir

Mir (pronounced "mere" - "Peace" in Russian) is the Russian Space Station.
It's been in orbit since 1986.  All recent Russian Cosmonauts have been hams
and have callsigns with "MIR" in them, such as U2MIR.  Mir has 2-meter
equipment on board and they operate packet and voice on 145.55 MHz.  (This is
the same freq as the Space Shuttles.)  The cosmonauts also have a digital
voice recorder which can repeatedly transmit voice announcements.

The best way to get a QSL card from Mir is to connect to their TNC's mailbox,
R0MIR-2, (That's R Zero MIR) leave a message AND GET A MESSAGE NUMBER.  You
must have the message number to qualify for a QSL.  The TNC is often busy
because amateurs forget to disconnect before Mir goes under their horizon.
In a case like this, try connecting to yourself or a friend VIA R0MIR.  And
if you hear a heavily accented voice calling CQ, by all means say hello!

70 cm and ATV gear is being prepared for future flights!

QSL Address:
Sergei Samburov (RV3DR)
Prospect Kosmonavtov. d.36, kw.96
Kaliningrad City, MOSCOW 141070, RUSSIA.

Sergei can also be reached via packet radio as RV3DR @ RK3KP.#MSK.RUS.EU

A special note on calculating Mir's orbit: Mir is big and it's in a low
orbit.  This means that there's a lot of atmospheric drag and it has to fire
its rockets every month or two to boost itself back up or it would have
re-entered and burned up long ago.  Unfortunately, whenever this happens, it
throws off all pass predictions.  When this happens, Mir will arrive LATER
than predicted, so if you tune to 145.55 and nothing happens at the predicted
time, keep waiting, it may be along in 10-30 minutes.

SEEING MIR: Mir is also the only EZSAT that can bee seen.  Mir is very big,
about the size of a semi-trailer, and when it comes over just after sunset or
just before sunrise, you can often see it go by.  This is because Mir will
still be in sunlight while you're in the earth's shadow.  In these cases, Mir
looks like a very bright star gliding across the sky.  It's a beautiful sight
and well worth looking for.  It's best to use a tracking program set to
VISUAL to find visible passes.  The best such programs will even draw you a
star map and show you Mir's path across it.  Don't forget to tune to 145.55
when you see it.  Also, don't forget to get on the local repeater and tell
people when you spot it so that others can share in the fun.

OSCAR-21, RS-10/11, RS-12/13

These three satellites are all in 600 mile high polar orbits, which carry
them over the US six to eight times a day for 10-18 minutes at a time.
They all have orbital periods of about 95 minutes and we typically get two
sets of three or four passes spaced 95 minutes apart.  The two sets of
passes are spaced 12 hours apart and their passes come a little earlier each
day because their orbits don't take quite exactly 95 minutes.

These satellites all have a coverage circle about 4000 miles in diameter, so
when they're about the horizon, you can use them to work hams anywhere in the
continental US, Canada, Alaska, Mexico, Central America, South America down
to the Equator, the Caribbean, Greenland, Iceland and parts of Scandinavia.
Eastern hams can work Europe and the West can work Hawaii.

All of these satellites are in boxes that are bolted to larger Russian
satellites and draw their power from the large satellite's solar cells.
They are VERY easy to hear and fairly simple to work.

OSCAR-21

My favourite satellite.  This is a German/Russian radio that uses a Digital
Signal Processor (DSP) chip and it is Flexible with a capital "F"!  It was
launched in January, 1990 configured as a linear translator which received a
band of 70 cm CW and SSB signals and relayed them on 2 meters.  The bird was,
to put it mildly, under-utilized.  Then in 1992 the DSP chip was reprogrammed
in orbit into a cross band FM repeater!  If you've been wondering if DSP is
as powerful as you've heard, now you know!  In the past year, it's telemetry
has been re-programmed from an obscure format to standard 1200 baud packet.
WEFAX pictures (which are uploaded by the ground controllers) were added in
December 1993.  (This is the same format used by many weather sats and short
wave weather stations.)

OSCAR-21 has an input frequency of 435.016 MHz, but 435.015 works just fine.
It's output frequency is 145.987 MHz, but 145.985 or 145.990 will receive it
quite well.  It has a strong transmitter and a ground plane antenna and most
HTs have no trouble picking its signals up when it passes over.  Mobiles and
base stations with omni antennas will receive it full quieting.  You can get
into this bird with 20 watts and a six element beam antenna.  I mount my beam
on a photo tripod next to my car and run coax to my dual band mobile.  You
have to point the beam accurately, so I take a list of altitude and azimuth
bearing generated by simple tracking software out with me and re-point the
beam once a minute.  In one summer, I worked the east and west coasts,
several Canadians, Texas and Guantanamo Bay, Cuba before fall's cold weather
drove me indoors.

Some OSCAR-21 tips: you can hardly get a word in edgewise during "prime time"
opening passes.  Try the late night passes instead, they're much less
crowded.  OSCAR-21's transmit and receive polarity rotate constantly during a
pass.  Mount your beam so you can easily rotate it for the best signal.
Remember, all these ham sats are full duplex, so you can and should monitor
your signal on the downlink.  (Use headphones.)  Turn the beam for minimum
noise.  You'll probably have to modify your dual band rig to get it to
transmit on 435.015.  BE CAREFUL because FM is generally NOT appreciated
below 440 MHz.  Also, the mod may allow you to transmit out of band, which is
a real no-no.

OSCAR-21 is also known as RS-14, AO-21 and Rudak-2.  It's bolted to a
satellite called INFORMATOR-1, which is often abbreviated INFORMTR-1.  It's
NORAD ID number is 21087.  Be careful, the rocket booster that launched the
satellite is still up there and it's named INFORMTR-1 R/B in some element
sets.  Your tracking program may find it instead of the satellite if you're
not careful.

RS-10/11

This is probably the easiest satellite to work of them all.  It has an
incredibly sensitive receiver that can pick up the faintest two meter signal
and relay it on ten meters.  There are documented examples of people having
QSOs on RS-10/11 by clicking Morse on HTs with rubber duck antennas!  I
guarantee you that your HT can put a useable signal into RS-10/11, I've done
it myself.  WARNING: if you try this, disable the microphone so you don't
transmit any FM sidebands and turn your CTCSS (PL) OFF!

RS-10/11 (Radio Sputnik) is for CW and SSB signals, so an all mode 2 meter
rig is ideal for transmitting to this bird.  The input bandpass is from
145.860 - 145.900 and the output freqs are from 29.360 - 29.400 MHz.  There
is also a morse beacon at 29.357 MHz.

RS-12/13

A cousin to RS-10/11, RS-12/13 is also a 40 KHz wide linear transponder.
However, this bird is unique because its input frequencies are in the fifteen
meter band!  This is also the only ham sat in the sky that requires more than
a code free technician license to work it, because its input band is from
21.210 - 21.250 MHz.  This straddles the Advanced and Extra portions of the
15 meter band.  Its output freqs are from 29.410 - 29.450 MHz.  Because of
skip, this satellite can often be heard and worked when it's below the
horizon!  At least one person has earned DXCC on this satellite!  RS-12/13 is
bolted to the ?????? ???? satellite and its NORAD ID is 21089.

DOVE

DOVE is a transmit-only hamsat.  It has no user accessible receiver.  Built
in Argentina, DOVE was launched in 1990 as a goodwill satellite.  It was
originally intended to transmit digitized voice messages that could be picked
up by students with simple receivers.  Unfortunately, the digital voice
hardware and software has been a constant source of problems since launch.
Attempts to get DOVE to works properly are proceeding as this is written, so
the best bet is to tune your 2-meter rig or scanner to 145.825 MHz and see
what the bird is up to currently.  Be ready for Morse, standard 1200 baud
packet or (with luck) digitized voice messages.  The signals are strong
enough so that an HT with a rubber duck will hear it when it's overhead,
although ground plane antennas will give better coverage when the bird is
near the horizon.

ANTENNAS:

For AO-13, the consensus is get to get KLMs, Telex/Hy-Gains, or roll-your
own,  Nobody liked the Cushcraft satellite antennas - they appear to have
problems in wet weather.  Bigger is also better, if you have the space.
Several people mentioned the KLM 22C and 40CX pair as excellent performers
(again - you need the room for those long booms!)  KE4ZV stated his pair of
KLMs (the big ones!) lets him work AO-13 with 3 to 30 watts (hardline feed
and rigorous attention to routing the feedlines and cables properly to
maintain the antenna patterns helps, too.).  Others mentioned the KLM
14C/18C pair as good performers - but you need more power on the uplink.

Telex/Hy-Gain antennas were recommended by several people as a less
expensive alternative to KLMs that work almost as well.  There's also M2
(started by an engineer from KLM).  While no one who responded uses them,
the information I received from a call to their factory in California
suggests they are comparable to slightly better than the KLMs in performance,
and about the same in cost.  Dave, WB6LFC, said homebrewing antennas is also
feasible - it takes work, but attention to detail results in top-notch
performance for very little money.  Finally, Ross, VE6PDQ, reported good
results using a pair of Cushcraft 215WBs on receive.

Problems encountered with AO-13 antennas include routing cables and
feedlines off the back of the antennas (to preserve antenna patterns), use
of fibreglass cross booms, mounting preamps as close to the feedpoint as
possible, and long antenna booms drooping.  (Gary, KE4ZV, recommends using
a rope to brace the boom or stiffening booms and fibreglass masts internally
with foam-in-a-can insulation.)

On antenna rotators, it appears the Alliance UD-100 is no longer made,
though it should still show up at hamfests.  People with long-boom antennas
report the Alliance rotator is too weak to move a big array anyway, and
recommended Yaesu's elevation-only rotator or their Model 5400 azimuth-
elevation unit.

Antennas for the low-altitude satellites appear to be much less critical.
J-poles were most frequently mentioned (the design from the AMSAT Journal?),
but dipoles, ground-planes, and yagis are also in use.  Several people work
RS-10 quite well with antennas in the attic.  Best results are with
steerable antennas, but the high operator workload during a pass (unless
the satellite is just grazing your access circle) almost demands computer
control of the rotators.

More to come soon...