AO-40 S-Band receiver tests - 23 Feb 2003
The first test of the AO-40 S-Band receivers was performed on 23 Feb 2003. Since the receivers would have been blocked by the S2 transmitter, the test used the K-Band transmitter to relay the signals. In response to a request from W4SM, a number of stations prepared for this test over a 2 week period. Stations known to be participating were W4SM (command), N1JEZ (K-Band receive), I8CVS (S1 transmit) and G3WDG (S1 transmit / K-Band receive).
At G3WDG, preparations included repairing the DB6NT 24GHz preamp, removing insects from the dish feed, and retuning the 13cm transverter from 2320MHz to 2400MHz.
The test started with 2 MA units of S-Band / K-Band beacons only. I used this period to align the dish carefully first on S-Band, enabling the K-Band signals to be found. The dish feed consists of a 24GHz horn looking through the centre of the S-Band helix, so the beams on the two frequencies are exactly aligned. The K-Band horn deliberately under-illuminates the 10ft dish to make pointing easier (making it operate something like a 5-6ft dish). Once the dish had been lined up, the K-Band beacon was running approximately 15dB above noise (2.5kHz bandwidth). This was the best I had heard it since the power loss event last year.
Stacy then commanded the S2 transmitter OFF and connected the passband to the K-Band TX. The beacon was left on to assist dish tracking. Signals were heard on the passband almost immediately - both my own ssb signal and Domenico's cw. Both signals were quite strong, and both of us were suppressing the beacon by quite a few dB (this is normal for the K-Band transmitter which operated as a limiting transponder). Both I8CVS and I were running about 8W output power, to 4ft and 10ft dishes respectively. Domenico then switched to ssb, and the wave file is a short recording of both of our signals.
N1JEZ also copied I8CVS and G3WDG during these tests.
Photo shows the temporary (!) installation of S Band TX on a workmate at the back of the dish. Blue box is the 144-2400 transverter with about 10mW output. On top of this is the PA ( 10mW to 1W amp driving 10W amp). Prime mover is IC202 in the shack (100m away from dish). Behind and above is the permanent installation of the 24GHZ transverter. PA was running about 8W out in this set-up (normally tuned for 2320).