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SATELLITES
Brief over view of contacts via various Amateur satellites

Satellite communication

First attempts during 1979 with both the AO-7 and AO-8 satellites proved successful even with the very modest equipment at my disposal. The up-link was easily established with only 10 Watts SSB (Single Side Band) on the 2 metre band with a Kenwood TS700 transceiver, but more surprisingly good signals were recovered on the 10 metre band down-link from the less than ideal Yaesu FRG-7 general coverage communications receiver. AO-7 and AO-8 were in my opinion one of the most accessible amateur satellites due to the choice of the 2 metre band uplink and 10 metre band down link which had the advantage of suffering much less Doppler shift than the use of higher bands on later satellites.  The choice of bands were also consistent with what the typical amateur station may have had on hand in that era. These satellites with an orbit altitude of around 700km are designated a LEO (Low Earth Orbit) type satellite which has a foot print, depending on the orbital pass of most or all of Australia or part of Australia and New Zealand.

The AO-7 and AO-8 transponders were designed to pass a band of frequencies 100 kHz wide enabling many stations to operate simultaneously in various modes which were generally CW or SSB.

The downlink was 29.450 - 29.550MHz and the uplink frequency was 145.900 - 145.800MHz.

Much later and after quite an absence from amateur radio I found an equally accessible satellite in UO14 and established many contacts from 2001 through to 2003 again with modest station equipment. UO-14 using exclusively FM was almost an orbiting repeater of the type familiar to most amateurs except that the input or uplink frequency was on VHF (145.975MHz) and the downlink was on UHF (435.070MHz). With an output power of 1 Watt and an orbit altitude of around 800km signals could be weak when the satellite was near the horizon where it would be typically many thousands of km away. This is obviously where the longest distance contacts could be made and where dedicated satellite stations with their steerable high gain antenna systems had all the success. Unfortunately UO-14 had catastrophic electrical failure in late 2003 and has not been heard from since!

In 2004 I was ready to tackle the high frontier with the initial trials of the steerable high gain Patch Antenna to access AO-40. AO-40 was a semi geo synchronous satellite in a highly elliptical orbit between 800km (Perigee) and out as far as 60000km (Apogee) with a range of transponders presenting pass bands similar in principle to the old AO7 and AO8 birds.

With another station monitoring the downlink frequency of 2401.335 MHz and with the satellite at Apogee (Maximum distance from the Earth) I commenced a test transmission on 435.7MHz with 30 Watts resulting in LILUC the satellite power management system warning that I was over loading the uplink. After winding back the power to around 8 Watts I had a sufficient quality down link return signal to carry out contacts too the part of the world that was visible to AO40 at the time, which was half the globe. With the completion of my 2.4GHz downlink dish antenna only days a way the unfortunate news was that AO40 was lost after a major electrical management failure. With no high altitude satellites available all the gear has been placed in storage awaiting the successful placement into orbit of the next semi geo synchronous amateur satellite, hopefully in 2009.

FO-29 is a LEO (Low Earth Orbit) orbiting at an altitude between 700 km and 1322 km and a similar concept to the earlier AO7 and AO8 satellites with uplink pass band between 145.900 -146.000 MHz and a down link pass band between 435.800 - 435.900 MHz and again targeted at CW and SSB modes. I established a number of successful contacts via this satellite during 2005, but found that the Doppler affect at these higher frequencies meant that I need to constantly retune the receiver to resolve the SSB signal as it wandered across the band. Many stations have had a lot of success with this satellite by employing complete computer management of the antenna tracking and the radio to track the receiver to compensate for the Doppler shift.

In late 2006 AO-51 became available and like UO14 it is designated a LEO (Low Earth Orbit) satellite with a typical altitude of around 800km. AO-51 with a analog uplink of 145.920 MHz FM and a downlink of 435.300 MHz FM is now amateur radio’s most accessible satellite

Software

Satscape is my preferred satellite tracking software partly as it is a Freeware program, however mostly as it is very user friendly and produces truly stunning displays. Satscape is constantly being improved and is supported by an equally stunning web site.

http://www.satscape.info/modx/index.php

 

Orbitron is a satellite tracking system for radio amateur and observing purposes.

http://www.stoff.pl/

 

Live OSCAR Satellite Status

This web page was created to give a single global reference point for all users in the Amateur Satellite Service to show the most up-to-date status of all satellites as actually reported in real time by users around the world. Please help others and keep it current every time you access a bird.

http://oscar.dcarr.org/

 

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Page last revised 06 January 2011 
 

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