OPERATING PROCEDURE.
THE RS - AND FO - SERIES OF SATELLITES.
For many years the Russian RS (Radio Sport) series of satellites were the most
popular for radio amateur operators. These satellites had LINEAR transponders
with extremely sensitive receivers. They could be worked with a minimum amount
of equipment at the ground station and were therefore the most logical place for
the newcomer to begin.
These excellent satellites were in LEO sun synchronous
orbits ... which means they "appeared" at more or less the same time
each day ... usually with about 8 useful orbits a day ... they had slow rates of
Doppler, were easy to track and didn't need sophisticated antennas. Not only did
they provide "local" contacts within Europe they also provided DX
contacts with daily QSO's between Norway and Japan or the UK and the USA.
There have been several RS satellites but the most popular one by far was RS-10
with it's linear non-inverting transponder operating with an uplink on 2m and a
downlink on 10m ... this allowed the new beginner to operate DX satellite
contacts using minimal equipment and very low power.
RS-10 was followed by RS 12/13 which was a satellite with pair of linear
non-inverting transponders aboard the commercial Russian COSMOS spacecraft.
RS-15 and RS-16 were also part of the Russian amateur radio satellite program.
Common to all the RS satellites was the ability to switch satellites and modes
to suit the orbit parameters. As well as very sensitive receiver and excellent
transmitters they also had a ROBOT mode that allowed automatic CW contacts ...
and subsequent QSL's from Moscow.
As can be imagined, these satellites were the perfect tool for mapping
propagation as well as providing interesting QSO's on CW or SSB from "down
the road" or intercontinental QSO's.
RS-10 stopped operating in 1997 and RS-12 to RS-16 a couple of years later.
Unfortunately, the Russians haven't maintained an amateur satellite program.
Although these RS satellites are now obsolete ...they are sorely missed .(
LA2QAA & GM1SXX)
The operating practices used on them will be included here to illustrate the
recommended operating techniques for satellites in general, likewise, the
transponder details ... in case any organisation decides to orbit satellites
that the amateur community really wants and needs.
RS-12/RS-13.
RS-12 and RS-13 were two independent amateur transponders riding piggyback on
the same commercial Russian COSMOS communications satellite circling the earth
in a POLAR orbit.
RS-12 could operate in mode-K or mode-T and could be switched by the ground
control station. The transponders were non-inverting ... that is to say, tuning
the uplink HIGHER would result in a HIGHER downlink.
Logically, an INVERTING transponder is the opposite, tuning the uplink HIGHER
will result in a LOWER downlink. This is useful to help combat the DOPPLER
EFFECT. On a non-inverting transponder if you transmit USB on the uplink you
will receive USB on the downlink, whereas on an inverting transponder the
opposite applies ... transmitting LSB on the uplink will result in USB on the
downlink.
Again, the reason that some transponders operate as an inverting transponder is
due to the fact that by using this system one can compensate for high Doppler
rates on the higher frequencies ... this will be more fully explained in a later
chapter.
The frequencies used for RS-12 operating were as follows ...
MODE-A Uplink 145.910 - 145.950 CW/SSB. Downlink 29.410 - 29.450 CW/SSB.
Mode-K. Uplink 21.210 - 21.250 CW/SSB. Downlink 29.410 - 29.450 CW/SSB.
Mode-T Uplink 21.210 - 21.250 CW/SSB. downlink 145,910 - 145.950 CW/SSB.
Beacon: 29.408 MHz (CW).
Robot-K Uplink: 21.129 MHz (CW).
Robot-K Downlink: 29.454 MHz (CW).
The ROBOT was an automatic CW answering machine. An explanation of how to use it
is given later.
Equipment.
As can be seen from the transponder frequencies one can utilise equipment
already available in most amateur shacks. For mode-K all that was required was
two HF links ... the Uplink in the 15m band and the Downlink in the 10m band.
It was even possible to use a single modern rig with dual VFO's, one tuned to
each band as long as one was aware that when using this method one had the
problem of not being able to hear oneself through the transponder simply because
a single rig can only operate semi-duplex ... which means ... you can't hear
yourself and since RS-12's Doppler shift was between 7 and 10 KHz ... depending
on where in the orbit the satellite was, in relation to your QTH ... you would
have had to 'guess' the offset.
Using two rigs .. or .. a rig equipped for satellite operations .. you can
adjust for Doppler shift as necessary because you can hear yourself! .. (full
duplex) .. just as everyone else can hear you .... it's just like a telephone
where you and the person you're in QSO with can speak at the same time.
The MAXIMUM power that should be used on ANY satellite should NEVER exceed that
of it's beacon ... you should adjust your EIRP (effective isotropic radiated
power)to be equal to the level of the beacon .. use it as your reference to
adjust your power.
As an example or EIRP, there are several permutations of radiating say 80w ERP
... for instance .. 80 watts to an omni-directional ground plane or 8 watts to a
10Db gain beam antenna.
A ground plane antenna is easy to construct or install but has the disadvantage
of needing a lot of power, most of which is 'wasted' in 'unwanted' directions.
Despite that it has the advantage of needing no rotor. Conversely, a beam has
the advantage of requiring less power but needs to be rotated.
A LEO satellite like RS-12 moves fairly rapidly across the sky .. a typical pass
taking approximately 18 minutes from horizon to horizon ... sometimes the
satellite would just graze the horizon and never actually pass near or over your
QTH...other times ... depending on the orbit ... it would pass right over your
head!. Remember, the orbit is constant but the earth moves within it ... by
studying a globe and imagining it turning within a polar orbit you will
understand why satellites sometimes appear to be low on the horizon and
sometimes right over your head.
Obviously...horizon passes allow QSO's at greater distances than overhead passes
.. but the possible communications time is reduced.
As mentioned previously .. Doppler effect on the RS satellites was between 7 and
10 KHz, this was due to the satellites motion in relation to your QTH. As a
satellite APPROACHES you the nominal beacon frequency will be slightly HIGHER
and as it RECEDES ... the frequency will be slightly LOWER ... the
frequency will be exact ONLY when the satellite is directly above you ... or ...
at the closest point of approach to your QTH. As the satellite comes over the
horizon the frequency will change SLOWLY and as it approaches you the rate of
change ..(Doppler).. will start to increase, reaching a maximum at closest
approach. As it recedes the Doppler rate will slow down again until it is
minimum just as it passes below the horizon again.
A ground plane type of antenna...(depending on the number of radials) ...has a
vertical radiation angle of approximately 19 to 25 degrees over the horizon. It
is a fairly good antenna for low horizon passes but is almost useless on passes
that are above 60 degrees. Obviously a beam that one can turn in azimuth and
elevation is the optimum but a turnstile type of antenna can also be used for
high angle passes. The LA2QAA satellite quad ... (see 'SIMPLE CONSTRUCTION
PROJECTS' is probably the best compromise between a ground plane and a turnstile
type of antenna ... neither of course being as good as a beam.
IT IS NOT MANDATORY to have high priced equipment, beams and rotors to use
simple satellites like the current HAMSAT which resembles the RS series of
satellites ... good DX QSO's can be achieved using simple aerial systems.
DOPPLER ... (This will be fully explained in a later chapter).
Due to the Doppler effect, you and the station you're in QSO with will be
operating on slightly different frequencies. This is due to the fact that the
distance from you to the satellite and the distance from your QSO partner to the
satellite are constantly changing, giving therefore a slightly different Doppler
effect as the satellite progresses along its orbit.
So how do you maintain contact when the frequency is constantly changing?
Like this:.....
(NOTE ... These frequencies only applied to RS-12 but the principle for any
satellite is exactly the same).
First, tune to the beacon frequency of 29.408Mhz and note how the frequency
changes ... slightly higher at the start of the pass but ALWAYS moving lower in
frequency. When you're familiar with the rate of change ... tune your RECEIVER
to 29.420 MHz and your transmitter to 21.220 MHz .... send a few dits with your
key and fine-tune your transmitter until you can hear yourself.
It is highly recommended that you get into the habit of using headphones.
This is to ensure you don't get feedback from the speaker into the microphone
causing a feedback loop between you and the satellite.
Once you can hear yourself you keep the RECEIVE frequency CONSTANT and tune the
TRANSMITTER frequency only, to adjust for Doppler effect. It may seem difficult
at first but you'll soon get the hang of it.
Make a mental note of the way to tune for Doppler on RS-12...and STICK TO IT!
If everyone follows the same convention there will be no problem .. if not ..
operators will find themselves 'drifting' across QSO's already in progress and
causing QRM. Since everyone can hear everyone else in full duplex ...
(satellite) QSO's there is ABSOLUTELY NO EXCUSE FOR QRM. Always listen before
you transmit.
(NB. Since this information was first published dedicated satellite rigs are now
available that allow automatic doppler tuning via software).
Don't be surprised if you receive a signal report of 539 when you're hearing
yourself at 599! ... there can be reasons for the discrepancy .....
(1) your QSO partner may have a poor receiving antenna ... (2) remember the
signal is passing through the ionosphere twice! and the state of the ionosphere
may be quite different between your QTH and the satellite and that of your QSO
partner's.
OPERATING THE ROBOT. (RS-12).
The ROBOT or autotransponder is an onboard computer allowing you to have
'contest' style QSO's with the satellite.
(Note that this is a good way of checking propagation).
Assume the ROBOT is operating in mode-T. Tune your transmitter to 21.129 MHz and
your receiver to 145.912 MHz ... taking into account the Doppler effect, send a
few 'dits'... just a few! ... until you can hear yourself in the Downlink window
.... (the Uplink window is between 2 and 3 KHz wide) .... tune a couple of KHz
'low' when the satellite is approaching or a couple of KHz 'high' if it's
receding.
When you hear the ROBOT calling CQ .... call the satellite using between 10 and
30 wpm thus ......
RS-12 DE LA2QAA AR....(the
AR sent as a single symbol).
If the ROBOT 'hears' you it will acknowledge your call with ..... LA2QAA
DE RS-12 QSO Nr *** OP ROBOT TU FR QSO 73 SK
the *** being a QSO number that is incremented after each QSO.
The ROBOT may ask you to QRS or QRQ ..... (higher speeds usually mean less
interference)...respond as requested.
DO NOT SEND A PERMANENT CARRIER ON THE UPLINK FREQUENCY.
After 'x' number of QSO's the ground (control) station downloads the computer's
'memory' and in due course you will receive a QSL card from Box 88 in Moscow.
The BEACON always transmits the current operating mode in CW.
The ROBOTS in the other modes operate in exactly the same way....just take into
account which mode is switched on at the time you wish to operate and check the
frequency list for the appropriate ROBOT combination of frequencies.
That's all there is to it. Remember ... practice makes perfect. It may seem a
little difficult at first but after a few successful QSO's you'll get the hang
of it. As mentioned...operating the ROBOT is an excellent way of studying the
idiosyncrasies of the ionosphere.
Sadly, the other RS satellites with the
exception of RS-15 are now non-operative.
RS-15.
Operating procedure for RS-15 is exactly the same as it was for RS-12.
Due to battery problems the signal from RS-15 can be quite weak...depending on
how much sunlight the solar panels 'see' ..however...though it may be difficult
to operate SSB sometimes...due to its lower power requirement CW is the
predominant mode of operation.
Test your skill with QRP SSB on RS-15.
See the frequency list for the transponder frequencies used.
RS-16.
Again, operating procedure is as RS-12 and RS-15 but RS-16 was the first Russian
satellite to carry a 70cm beacon. Sadly, this satellite too is now
non-operational.
FO-20.
FO-20 operating is a bit more difficult than operating on the RS-satellites; the
main reasons being the higher Doppler effect due to the higher frequency used on
the Downlink, the slightly more sophisticated equipment used and the fact that
FO-20 has an INVERTING transponder.
FO-20's Doppler effect is twice that of the RS satellites ... plus/minus 20 KHz
in the space of a pass. There are two 'conventions' for Doppler tuning...
1) The European stations tend to tune the transmitter ... (an old AO-13 habit
from mode-B operating) ... and leave the receiver on the same frequency.
2) The American convention however is just the opposite!. The Americans 'tune'the
receiver and leave the transmitter on the same frequency. This is because of the
fact that it is easier to tune for Doppler by tuning the 'higher' of the two
frequencies ... simply because the higher the frequency . .the more extreme the
Doppler. Perhaps that is why the 'habit' of the European operators is to tune
the transmitter regardless! .... after all .. mode-B is the exact opposite of
mode-J. This can be quite confusing for the newcomer .... the easiest way to
remember it is .... .whatever! the mode .... 'tune' the higher frequency and
leave the lower frequency constant.
Therefore on FO-20 in mode-J....TUNE the receiver (highest frequency) and keep
the transmitter (lower frequency) constant. The reason FO-20's transponder is
INVERTING is simply because by inverting
the transponder frequencies one helps to alleviate the high rate of Doppler
Note that on an INVERTING transponder LSB on the
Uplink will give USB on the Downlink.
Modern synthesised rigs designed specifically for satellite operating have a
separate transmitter and receiver in the same package and can be 'tuned' so that
as one VFO on one band goes higher in frequency while the other on a different
band goes lower by the corresponding amount...giving an automatic Doppler
correction.
Since most newcomers don't own such sophisticated equipment ... here's how to do
it by using separate rigs.
Print out the following table of FO-20's operating frequencies
...and remember to take into account that it is an INVERTING transponder.
Frequency Table for FO-20
FO-20 (INVERTING) TRANSPONDER FREQUENCIES.
Uplink. Downlink.
145.900 435.900 SSB
145.905 435.895 SSB
145.910 435.890 SSB
145.915 435.885 SSB
145.920 435.880 SSB
145.925 435.875 SSB
145.930 435.870 SSB
145.935 435.865 SSB
145.940 435.860 MIXED
145.945 435.855 MIXED
145.950 435.850 MIXED
145.955 435.845 MIXED
145.960 435.840 MIXED
145.965 435.835 CW
145.970 435.830 CW
145.975 435.825 CW
145.980 435.820 CW
145.985 435.815 CW
145.990 435.810 CW
Beacon 435.795 CW
Assume you want to operate SSB ... the FIRST! thing to do is tune in the beacon
on 435.975 and make a note of the signal strength and the speed of the
Doppler.
After getting a general idea of the Doppler speed ...... tune your receiver to
435.880 ... (or any unused frequency on the Downlink) .... if you've tuned to
435.880 ... look at the list and note the corresponding Uplink frequency will be
145.920. Tune your transmitter to that frequency. Taking into account the
Doppler effect ...send a few 'dits' and tune around until you can hear your own
signal in the passband. Switch to LOWER SIDEBAND and listen to your own signal
on the Downlink in UPPER SIDEBAND ... (remember, you're using an INVERTING
transponder) .. tune slightly until your Downlink signal sounds 'normal'.
If the frequency is still clear at this time ... you can start calling CQ
...
It is wise to call 'CQ FO-20' .. because you're transmitting in the 2m band and
any 'local' 2m stations will realise you're calling for 'satellite' QSO's and
will therefore not 'reply' on 2m ... not that they should! because the frequency
is in the satellite sub-band and terrestrial operators normally won't operate
there anyway.
All modern tracking programs for computers tell you which frequency to transmit
and which frequency to receive on ... as well as telling you the Doppler effect
at any given moment. IT is NOT mandatory to use a tracking program ..
there are several ways to track a satellite without using a computer .. a
computer is a good 'tool' though and will be dealt with in the TRACKING chapter.
Remember you're on an INVERTING transponder so that if you wish to move LOWER in
frequency your transmit frequency must be INCREASED accordingly .. and
vice-versa.
Get into the habit on FO-20 .. (mode-J)...of FIXED TRANSMIT frequency and
ADJUSTABLE receive frequency.
(Opposite to mode-B where the frequencies are reversed).
Be aware though .. some operators .. mainly European .. use the mode-B
convention on FO-20 and some use a combination of both! .. using the 'wrong'
combination leads to unnecessary QRM due to the fact of QSO's 'wandering' across
the passband due to Doppler effect and 'retuning'.
If everyone followed the same convention this 'problem' would not occur.
Again .. practice makes perfect.
GET INTO THE HABIT OF USING HEADPHONES so you don't get 'hit' by the feedback
loop.
EQUIPMENT NEEDED FOR FO-20.
Obviously one needs a 2m transmitter and a 70cm receiver as well as some method
of knowing where the satellite is/where to point your antennas etc if you're
using beams. As mentioned, 'tracking' will be dealt with separately in it's own
chapter but antennas can be mentioned here.
FO-20's beacon transmits with 1 watt so don't expect 60 over 9 dB signals. A
single groundplane or omnidirectional antenna will give a weak signal into the
satellite using SSB but is 'just' adequate for CW operating. A 10DB gain beam is
recommended for both the Uplink and the Downlink signals
If you use
a 10Db beam on the Uplink .. NEVER transmit with more than about 20w from
the rig... (that's 200w ERP!) .. normally,
between 5 and 8w is adequate.
The beacon is only transmitting 1 watt!) .. in any case...YOUR DOWNLINK SIGNAL
SHOULD NEVER BE STRONGER THAN THE BEACON .. the beacon is your reference ..
using more power ensures you're an ALLIGATOR ...... DON'T DO IT!.
Where most newcomers go wrong is having inadequate receiving systems .. they
have to use more power to be able to hear themselves ..often not realising that
they're overloading the transponder and making life difficult for those using
adequate receiving systems. The receiving set-up is MOST important. Ensure you
can hear the beacon well before even considering the transmit side of the
station.
A good 70cm preamp is to be recommended though if you have a 70cm beam with 10Db
or more gain it can be more of a hindrance than a help .. due to the 'noise
figure' .. on 70cm a preamp amplifies the background noise as well as the
required signal.
Coaxial cable is both lossy and noisy at 70cm so invest
in the highest grade of cable you can afford. For short runs ..up to 15m in
length .. RG-58 is 'just' adequate at 2m but too lossy at 70cm ..where 'at
least' RG-213 should be used. At 70cm, BNC or N-type connectors should be used
.. DO NOT use so-called UHF types .. they are definitely NOT recommended above
2m .. and they are NOT waterproof.
Once again .. the first QSO will most probably be a disaster! .. mainly due to
Doppler effect .. but by the time you've got the 3rd under your belt you'll find
it an enjoyable challenge after operating the RS series of
satellites. Most people get 'hooked' on satellites at this point and want to
progress to the digital satellites ..WELCOME ABOARD!.
... AND NOW THE GOOD NEWS ...
FO-29 is the current Japanese amateur radio satellite and is a replacement for
FO-20. At the time of this writing (25.05.05) it is still alive and well. Though
the "digital" mode and the "parrot" mode aren't operating,
the mode-J (2m up/70cm down) analogue inverting transponder is still providing
excellent communications.
SEE ALSO "HAMSAT" ...
AO-27.
AO-27 is rather special in that it is using standard terrestrial FM in voice
mode .. i.e. .. a flying repeater with Doppler effect!. (The latest FM satellite
is AO-51).
Oscar 27 is a very popular satellite. Launched from an Ariane rocket by the
European Space Agency (ESA) it is onboard the commercial EYESAT-A satellite 800
Kilometres over the earth in a near polar orbit. (See ORBITS). The satellite is
also known as AMRAD AO-27. Interferometrics (Vienna) built the commercial part
of the satellite while students in McLean, Virginia built the amateur part. The
name 'Amateur Radio Research and Development' being AMRAD, hence, AMRAD AO-27.
AO-27 uses a 'bent pipe' transponder. (What goes in one end comes out the
other).
The 'bird' also carries a 1200 BPS digital transponder using FSK on the Uplink
and AFSK on the Downlink. However, the FM transponder is almost always the 'main
mode'. An on board computer switches the transponder on and off according to the
eclipse schedule, usually about 20 minutes after the satellite passes into
sunlight. That is to say, when the satellite is in darkness, it's switched off,
to conserve battery power. It switches on several minutes after entering
sunlight. The solar panels then recharge the battery.
The frequencies used on the analogue transponder are 145.850MHz FM on the Uplink
and 436.800MHz FM on the Downlink.
Many operators have copied AO-27's signals on their handheld and rubber duckie
antenna. A popular pastime is AO-27 portable. Where operators use two H.T.'s and
a single dual band antenna, a 3el: 2m yagi and 6 el: 70cm yagi on the same boom,
held in one hand and pointed at the satellite.
To operate AO-27. Check the schedule to see when the satellite will be in
sunlight and in range of your QTH. If you operate your 70cm rig with the squelch
open you will hear the satellite 'switch on'. If the frequency is clear you can
then call CQ. Remember that this is an FM transponder and just like a
terrestrial repeater only 1 person can operate at a time, therefore, be brief.
Again, just like an ordinary repeater, the satellite will capture the strongest
signal.
This is NOT an excuse to use excessive power, an absolute NO-NO for satellite
operators. As with all satellites, due to Doppler, the frequency of the Downlink
will be a few KHz high as the satellite approaches your QTH and will decrease in
frequency as it recedes. Since the mode is FM the Doppler will not be as
noticeable as it is on CW/SSB on for instance FO-20. A lot of modern rigs only
tune in KHz steps in the FM mode but this is no problem if you tune 5KHz high
i.e. 436.805MHz to begin with. You will hear
the squelch break in as the satellite Dopplers down, you then drop down KHz etc.
With a bit of practice you'll soon be able to anticipate where your receive
frequency should be set.
Remember that the satellite's receiver is very sensitive so high power is NOT
necessary. (That applies to almost ALL satellites).
On AO-27, just a couple of watts are usually adequate for QSO's.
There are other satellites planned that use various modes of frequency and
communication combinations. See elsewhere in this book for planned projects.