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![Previous (earlier) Story](/images/sty-down.gif "7 MHz "Realignment" Among WRC-2003 Advisory Committee Preliminary Views"){kind=small} Previous: 7 MHz "Realignment" Among WRC-2003 Advisory Committee Preliminary Views |  Next: The K7VVV Solar Update |
NEWINGTON, CT, May 4, 2001--The amateur community will get a chance to try out the AO-40 transponders this weekend. The AO-40 team has announced that experimental transponder operation will start on Saturday, May 5, at approximately 0800 UTC.
"We expect good conditions on Saturday morning over North and South America and Europe," said AMSAT-DL President Peter Guelzow, DB2OS, an AO-40 team leader. Guelzow said the 435 MHz and 1.2 GHz (L1-band) uplinks will be connected to the S2 (2.4 GHz) transmitter passband.
It's estimated that AO-40 will be available on May 5 in the Western Hemisphere from 0800 until approximately 1400 UTC. Stations should use only SSB and CW. Guelzow said it's expected the transponders will remain available over a period of approximately 10 days.
"Needless to say, we're all very excited," he added.
The uplink frequencies are 435.550-435.800 MHz and 1269.250-1269.500 MHz. The Downlink passband is 2401.225-2401.475 MHz. The transponders are inverting, so a downward change in uplink frequency will result in an upward frequency shift in the downlink.
Users are asked to avoid the "middle" 2.4 GHz telemetry beacon and give it a clearance of 5 kHz on either side. "If the beacon cannot be copied because of interference from transponder users, the passband will be closed and the transponder shut down," Guelzow warned.
He emphasized that the operation is experimental, the schedule subject to change, and the transponders could be shut down at any time without warning.
"The window for transponder operation is about 10 days, before we move to try to raise perigee using the arc-jet," Guelzow said.
The AO-40 ground controllers also plan to test the problematic VHF and UHF transmitters again, when the squint angle and visibility are favorable. "We will place announcement ahead of time, so that the 'big guns' can listen for weak signals," Guelzow said.
In other AO-40 news, AMSAT-DL reported the RUDAK experiment was powered up and made available to the RUDAK team for testing on May 1. The RUDAK--the German acronym stands for "Regenerative Transponder for Amateur Radio Communication"--is a digital transponder system that can be programmed to perform a variety of functions.
Jim White, WD0E, in Colorado reports reliable command results with the RUDAK-A processor on the L-band (1.2 GHz) uplink. "The gain of modulator 1 was turned up, and the resulting downlink at 2401.72 was usable for most of this period as squint angles improved below 50 degrees," he said.
This week White successfully loaded the primary housekeeping task on RUDAK-A, which is now sending telemetry and a pass-through of the IHU downlink.
White noted that while all testing during the period was successful, a lot remains to be tested and exercised. RUDAK-B software has not been loaded yet. James Miller, G3RUH, has reported good copy of the RUDAK 9k6 downlink.
"Please do not attempt to uplink to RUDAK until testing is completed, and it is made available for general operation," White said.
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