AO-40 Successfully Tests K Band Transmitter

NEWINGTON, CT, Sep 18, 2001--AO-40 ground controllers have succesfully tested the spacecraft's 24-GHz transmitter. The K-band transmitter on 24.048 GHz was activated September 9 on orbit 396 and connected to the passband and beacon inputs that feed the S2 (2.4 GHz) transmitter.

"The command team is delighted to report this additional functional transmitter on AO-40!" said Stacey Mills, W4SM. Commissioning of the K-band transmitter is the latest additional capability for AO-40, which was launched last November.

Mills said the passband and beacon were first detected at 1930 UTC by Petra, G4KGC, as the radio operator and Charlie Suckling, G3WDG, as the dish operator. "Shortly thereafter the beacon and passband were also detected by Michael Fletcher, OH2AUE," Mills said.

G3WDG and G4KGC were using a 22-cm offset dish and reported signals 6 dB above the noise floor. OH2AUE used a 60-cm dish and reported that the beacon was 7 dB above the noise floor under less than ideal conditions with overcast skies and occasional rain.

"Both used linear feeds and reported good, stable signals except for cyclic deep fades due to the linear polarization of the K-Tx antenna, the linear polarization of their feeds, and the rotation of AO-40," Mills said. "A circularly polarized feed should eliminate these spin fades."

Mills said that the RUDAK digital transponder was put back on line on orbit 399, with the GPS. "NASA has been very eager for data from the system." he noted. The K-band transmitter now is on from MA (mean anomaly--an orbital position--Ed) 118 to 138.

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