|Release: September 1997|
|First you need a little history of how Mir got on the Air|
The SAFEX team
designed built and delivered a working 2-meter station to Mir in
Soon Mir was on the air in Voice. The Mir frequency was chose by accident.
It seems the example the radio manual gave instructions on programming 145.550. During ground training, the Mir crews practiced using the example in the Manual. And that is where 145.550 simplex came from.
It is a pure coincidence that SAREX shuttle operations choose the same frequency.
The frequency 145.550 turned out to be a big success around the world.
There were few if any repeaters located in this part of the band.
In Europe the channel was near a popular Simplex channel. This was the only known complaint.
It seemed some of the simplex operators did not like to share the channel for the 10 minute passes (maximum usage in 24 hours is less than 60 minutes of Mir activity).
The SAFEX team then upgraded the Mir station to an easy to use 1200 baud packet station.
This was an excellent decision from the SAFEX team. Now for the first time, we have an easy to use, inexpensive FM "Easy-Sat".
Beginners from around the world, could not use either Voice or inexpensive 1200 baud packet to work a satellite. The Space Shuttle was also in operation, but because of a lack of Outside antenna, the Shuttle could not be considered an "Easy-Sat".
SAFEX had done an excellent job in putting Mir Voice and Packet on the air.
Stations from around the world began using Mir daily, we even got good results from fishing vessels out at sea.
|But then the problems began|
It seemed that few
people knew how to use the Mir Packet station properly.
Most stations did not realize that the Mir PMS was a Single user Mail box.
Only one stations is allowed to transmit to Mir at a time. As Mir became more popular, the ability to connect and Read or Send a message dropped to nearly Zero. The only time people could work Mir, was during the early AM hours on Weekdays, when Most people were asleep.
|Something had to be done|
This was when MIREX
Dave Larsen and Miles Mann began a program to teach people how to use the Mir PMS correctly.
Dave and Miles wrote hundreds of short articles about "How to work Mir" to be published on Packet and Internet. Miles wrote two very detailed articles which were published in QST and CQVHF.
After the QST article came out, many people in the USA began to start using the correct procedures.
Stations in the USA and other parts of the world became very courteous when operating the Mir PMS.
During prime time hours of 6pm - 11pm over the USA, it was possible to 6 to 10 people successfully logging to the Mir PMS and complete a transaction.
This success was a direct result of the training and informaiton provided by MIREX.
Lower power stations across the USA were having excellent results when the stations all followed the same procedures defined by MIREX. And the success were not limited to stations in the USA.
Many stations around the world began to follow the MIREX procedures for using the Single User Mir PMS and were having good success in their countries (South American, Australia, Canada, Asia Pacific, etc.).
|Intermittent Problems in the USA|
From time to time,
the courteous order for connecting to Mir would fall apart for a
This usually happened for three reasons:
Some Mir crews did not fully understand the benefits of the Amateur Radio station, and would shutdown the station for weeks at a time. When Mir came back on the air, the press generated by terrestrial Packet and Internet would generate an large number of beginners attempting to connect to Mir for the first time. Since the beginners did not know the proper porcedures, the reliability of connecting to the Mir PMS would drop, Temporarily.
When ever there was a SAREX Shuttle mission about the take place, the extra publicity would also generate a lot of intereste in the Mir PMS. This too would over load the abilityes of a Single user Packet system.
Robot operated much differently than the Mir PMS.
Stations would connect to Mir, expecting it to operate
just like the Shuttle and issue them a QSL number.
The Mir PMS does not issue QSL numbers.
After each one of
these incidents, the MIREX team and dozens of volunteers would
start reminding their local users as to the correct procedures.
After a few weeks, everything would be back to Normal, and the success of connecting and preforming a full packet transaction would increase. If was normal for a 25 watt station with a 0 gain antenna to connect to Mir and suscessfuly upload a Message to Mir.
|Problems in Europe|
I have a few reliable
contacts in Europe who would send me packet log files of Mir
passes on a regular basis. It seemend the recomendations made by
MIREX on how to operate the Mir PMS station were not widely used
in Western Europe.
Hundreds of stations would constantly blast the Mir PMS with packet connect requests.
The end result, was that only the hand full of Kilowatt stations could use the Mir PMS while Mir was in range of Europe. Another problem in Europe was a station called a "Mir-Hog" .
A Mir-Hog is a station that connects on just about every pass every day and then ties up the Mir resources and prevents other people from accessing Mir.
We had a few stations like this in the USA, but they would usually go off the air soon.
Amateur Radio Stations from around the USA would send USA-based Mir-Hogs reminder to let the other beginners have a chance.
Mir was unusable over Europe, proper training would have siginifintly reduced most of the problems.
The MIREX team did not have the resources to teach Europe. We expected the SAFEX team to be responsible for training European stations the correct procedures for using the Mir PMS.
This is when the first big mistake was made in frequency selection.
The SAFEX team incorrectly assumed that because they could not use Mir from Germany, that Mir was receiving interference from Simplex FM voice activity.
In reality, the interference caused by FM Simplex voice activity was minimal. The real cause of the inability to use the Mir PMS as primarily caused by Improper use of the Mir PMS by untrained Amateur Radio Stations.
The MIREX team informed the SAFEX team in 1995, that changing the frequency would not solve the problem. The SAFEX team would need to take a more proactive approach to training stations in Europe on the proper procedures for working the Mir Single user PMS Mail box.
The MIREX team began
experiments on attempting to configure the PMS to support
We quickly discovered that allowing multiple connects would not solve the problem.
Multiple connects requires multiple Uplink frequencies. One uplink frequency per user. MIREX is looking into a long term fix for this problem.
In the short term, Educating the Mir PMS users is the best way to get around the Single user single frequency problem.
The 2-meter Mir PMS is not designed for High volume traffic.
It is a beginners satellite designed to welcome beginners to the world of Amateur Radio satellites.
MIREX began to experiment with different 2-meter channels on Mir beginning in September 1992, when MIREX had its first School schedule with Sergej Krikalev.
Our first school schedule was using 145.525 Simplex.
However this channel did not work very well because of Packet QRM from 145.510.
At the time, Digital and Analog Repeaters were Illegal in the band 145.500 - 146.000 (USA FCC Law). Unfortunately the law is ignored, and now Packet Cancer has spread all over the 2-meter band in the USA.
MIREX was spending more time running school schedules around the world, and we needed frequencies that would work World-Wide. MIREX tested several channels between 144.300 - 144.500, and 145.800 - 146.000.
The Mir school frequency changes were kept a secret.
We did not want the school schedules or other tests interfered with.
The frequency 145.550 was still used a the Primary Public channel, as was successful world wide.
MIREX used these
quite channels to conduct may types of packet tests.
We would configure the TNC modem for different parameters, to try to optimize the packet data throughput.
We each Mir crew change, MIREX would give the new Mir crews additional training, etc.
We verified that Full two-way Packet Digi connects through Mir, were NOT practical, because it used up too much of Mir packet time to complete a simple message. Unproto proved to be much more reliable than fully two-way connects.
All of the data
collected by MIREX as sent to SAFEX and SAREX.
SAFEX was spending most of its time building new projects for Mir.
MIREX was spending most of its time supporting and testing the existing Mir Amateur Radio Projects.
The SAFEX team never
performed any extensive frequency tests with the Space Station
The only time 145.800 was tested, was during a short Holiday week, in December 1996.
The Mir crew installed a digital voice recorder. The recorder would play a short message on 2-meter every few minutes. The system was placed on 145.800 simplex for a few days.
Then during a New Years party on Mir, the equipment was damaged and a power supply and the digital voice recorder was destroyed.
|Interference from Mir Comm Links|
The MIREX team began
to hear there were problems with 2-meter packet, when Mir was
transmitting on their commercial channel 143.625.
The rumors indicated the 2-meter station on 145.550 would become deaf.
The information that
MIREX received about this problem was very limited, and the
problems only happened over Europe. We did not have problems with
143.625 over the USA and were not able to analyze the problem
Then NASA began remote comm links with Mir in 1996. Now Mir was active on 143.625 as it flew across the USA. More Ground links were being added world wide.
Soon many populated areas of the world, would have remote Mir ground links.
MIREX began testing
with the Mir crews late 1996. It was confirmed that when the
commercial link was active on 143.625, it was impossible to work
the Mir space station on any frequency below 145.900.
The frequency 145.940, was barley usable when the ground station was transmitting more than 3000 watts of ERP. The frequency 145.985 was chosen to keep the PMS receiver as far as legally possible away from the 143.625 transmitter. (ITU regulations control satellite down-link frequency ranges).
The frequency 145.985
is still jammed by the commercial transmitter, but intermittently
high power ground stations can get access. More testing is
required to determine how much power is required to capture the
MIREX is working on a filter project, that if approved, will solve the comm link interference problem.
MIREX still encourages stations to use as little power as possible.
SAFEX announced it would switch Mir to 145.200 uplink and 145.800 downlink on November 1, 1996.
This frequency was never tested to see if it could support world wide communications.
This frequency was in direct conflict with Amateur Radio band plans from around the world.
This frequency was only approved by IARU region 1. Regions 2& 3 did not approve this channel because of the numerous band conflicts.
Since 145.550 received interference from Mir transmissions on 143 MHz, then 145.200, would receive even more interference.
right next to an over crowed and uncoordinated APRS
When Mir began
testing 145.200/800 in November 1996, the problems over the USA
Problems in many other countries were also reported, but here are the most common problem in the USA.
There are approximate 300 repeater outputs between 145.190 and 145.210.
Some of the repeater outputs are even on 145.200.
Previous MIREX FM satellite tests have proven, that Satellite FM requires a Minimum of 25khz channel spacing (30khz is preferred).
When Mir is listening
on 145.200, Mir can hear hundreds of repeaters in its 1500 mile
The Noise from the repeaters prevents Mir from hearing any data or voice on 145.200.
When the crew used 145.800 to listen to ground stations, a similar problem occurred.
It is Illegal for repeaters to used 145.500 - 146.000. Packet repeats think they are immune from the law.
Now the whole area from 145.500 - 145.790 is being blasted by Packet Cancer.
AMSAT-NA and the ARRL failed to setup a buffer zone to protect the bottom of the weak-signal satellite subband.
The QRM from the
packet cancer is so loud, it interferes with A0-10 & A0-13 on
SSB/CW below 145.900.
The closer you are to 145.800, the greater the amount of interference.
When Mir Packet is listening to 145.800, the TNC modem hears all of the APRS packet coming from 145.790.
This QRM prevents the Mir TNC from transmitting until the built-in timers of the TNC force a packet burst every 2 minutes. When ground stations are trying to listen to Mir on 145.800, the same APRS packet QRM, prevents stations from hear Mir.
Even expensive radios and narrow band filters can not block out the packet QRM.
In April 1997 Mirex proposed a 30 day frequency test.
We would move Mir from the 145.800/200 split to 145.985 FM Simplex.
The test was a big success.
The Mir crews loved the new channel and they spent more time working the public on voice and packet.
When the 30 day test was over, the crew switched back to 145.800/200 for a few days.
Then the Mir crew deiced they would abandon 145.800/200, in favor of the successful channel 145.985 FM Simplex for all operations, voice and packet.
Reliable access to the Mir PMS reached an all time high during the summer of 1997.
The IARU-1 suggested channel for Mir 145.200/800 & 145.800 is Unusable for most of the world.
very pleased with the former operations on 145.550 (it
may be difficult to get the channel back now that it was
The frequency 145.550 was a good choice for most of the world, and it was easy for simplex operators to share the channel.
MIREX has tested several combinations of channels. And proposed these combinations to SAREX, SAFEX and AMSAT-NA. The workable options are currently very limited because of interference from the commercial link, but after the proper filters are installed on the Mir 2-meter station, a wider selection of channels will become available.
opposed to Split Band operations because it prevents
beginners from accessing Mir.
Without Satellite beginners, you will not be able to get much support for expensive satellites such as the yet to fly Phase 3D. Split Band operations requires radios with the ability to adjust 70cm frequency in 1khz steps. These radios are too expensive for beginners to use.
70cm test with Mir proved, that 70cm operations are
possible for experienced stations with the proper
However, over 70% of the existing Mir 2-meters users can not support 70cm.
The MIREX Team
|Last modify: 2001-02-13||Credits|