AO-40 transponders to open for experimental operation

The AO-40 team has announced that experimental transponder operation
will start on Saturday, May 5, at approximately 0800z. The
announcement comes in the wake of successful initial transponder
tests last weekend.




''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 uplinks
will be connected to the 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 1400z. Stations should use
only SSB and CW. Guelzow said it's expected the transponders will
remain available over a period of approximately 10 days.



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. Guelzow said the
transponder might be shut down if the beacon cannot be copied
because of interference.



He emphasized that the operation is experimental, the schedule
subject to change, and the transponders could be shut down at any
time without warning.



AO-40 ground controllers also plan to test the problematic VHF and
UHF transmitters again.