Amsat's Echo gets 'turned on'

AO-51 (AMSAT-Echo) will be turned on for general use in FM repeat mode on 30 July 2004 at about 0215 UTC.

This will be for a trial period of about three weeks during which the command stations will be watching the power budget and adjusting the UHF transmitter B power as needed for good management of the battery.

Initially, the transmitter will be running at about 1W.
If power allows, it will be slowly increased during the trial period. We will also be adjusting settings on the satellite, so if the signal changes slightly from time to time, do not be alarmed. The TXB transmitter will be on 435.300 MHz, which is also a trial frequency. The original frequency of 435.225 MHz is now in regular use by GO-32, so the alternate is being tested to see if it can be used long term.

To work Echo in this mode you need the following information:

Uplink: 145.920 MHz FM voice with 67 Hz PL.

Downlink: 435.300 MHz FM voice.

The downlink transmitter will come on when it hears an uplink signal with a 67 Hz PL tone for about 1 second.
It stays on for 10 seconds after that signal goes away.

This operation is just like a terrestrial FM repeater with a 1 second kerchunk filter and a 10 second hang time.

The command stations will be watching the AMSAT-BB email reflector for report of how Echo is working. Please post your results there. We are most interested in hearing about how well Echo hears you and how well you hear it.

Note that Echo is still wobbling a great deal and the polarization sense of the downlink will vary. The B UHF TX is nominally RHCP in the northern hemisphere but this will change over the duration of a pass due to wobble and orientation relative to the ground station.

Transmitter A will generally continue to operate on 435.150 but may be at reduced power at times, or may be at about 1W only when the command stations are gathering Whole Orbit Data (WOD) telemetry. We will be analyzing the
WOD for information about how much TX B is on and how the power system is behaving. Please note that the digital transponder and the store and forward BBS, are not yet open for general use. TX A may also switch to 38k4 from time to time to facilitate downloading large files.

We expect Echo will be heavily used in these first few days. Many stations will be trying to make a contact through Echo. It is good amateur practice and common courtesy to let everyone have a chance.

Echo will hear you as well as or better than any previous amateur FM repeater satellite. With the downlink transmitter at 1W you will need a small directional antenna to hear it. Especially in these first few days, always listen first. Even though the downlink will only come on when it hears an uplink signal, with hundreds of stations trying it out, we expect the transmitter to be on continuously when over populated areas. So again, listen first, and be courteous to let everyone have a chance at making a contact via AO-51.

And a reminder, this is a trial period of the FM voice repeat function. The digital portion of Echo is not yet open for use.

Echo Command Team
Jim White, WD0E
Mike Kingery, KE4AZN

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