|Field Day 2000 QSO Points|
|Total QSO Points||Power Multiplier||Claimed Score|
Note: Bonus Points Not Included
by John Gafford N5XAK
|by Bill Cox W5JRM|
First, I identified the RS-13 satellite as the bird of choice: It would have an ideal pass right over Waco during the event. It used 2m SSB or 15 m SSB uplink and 10 m SSB downlink. Since the 2m antenna is easier to direct at the satellite, we went with the 2m SSB uplink.
But I didn't have a 2-m SSB rig. Larry Bush, W5NCD to the rescue! Larry loaned me his Icom 2m all-mode transceiver and amplifier to bring the output power to about 70 watts. The 2m signal went into a 9-element horizontally polarized yagi aimed with an "Armstrong rotator" (manually aimed throughout the pass). It would have been nice to have a circularly polarized antenna, and a motorized rotator. Having neither, I shortened the yagi to 6 elements to broaden the signal beam width at the expense of a dB or so of gain. The received signal from the satellite was picked up by my Icom-728 HF rig connected to a 10-m vertical dipole.
RS-13 uses 145.96-146.00 MHz for uplink and 29.46-29.50 MHz for downlink. The lower halves of the bands are traditionally used for CW and digital modes, so SSB contacts are made in the upper halves.
The first thing to do was identify the satellite passes and practice, practice, practice in the week or two before field day to get down the technique. The Doppler shifting of the signals takes a little getting used to. I used my CW keyer to send out short strings of dits to locate the correct frequencies for TX and RX, and then called CQ (or answered a CQ). Because of the split band operation, you can (and must) hear your own voice coming back down on the 10-m band. As the bird passes over, you slowly adjust the TX frequency to keep the RX frequency constant. When the satellite is straight overhead, your uplink of 145.980 comes back down at 29.480. But at the start of the pass, the bird is coming right at you and so it sees your TX waves compressed (i.e., a higher frequency than you're sending). So you start the pass by sending a bit lower to compensate, say, at 145.974 MHz. Just before the bird drops below the opposite horizon, you'll have to compensate by transmitting a higher frequency, about 145.986 as your waves race to catch up to the bird. It helps to imagine how a fire engine might have to continually adjust the pitch of their siren if they wanted you to hear a constant pitched sound as it approached you and then zoomed by!
At the same time all of this is happening, since we're using the Armstrong rotator, we must pay attention to the pass geometry, and keep that 2-m yagi pointed as close as possible to the satellite's location. For that I used the beautiful STS-Orbit, a free tracking program originally designed for tracking space shuttles.
So how did it go? I made several contacts in the week preceding Field Day, and so was pretty confident that my setup was performing. When Field Day arrived, we had a beautiful opportunity in Waco, Texas: an ascending pass (up from the South) almost directly overhead. That meant we'd get first chance at RS-13 when it popped up to see the U.S. That advantage proved a necessity, as we made a very brief but all-important contact with another Texas station, K5VAS, in the first few seconds after the bird became "visible." As the bird rose higher in the sky, it quickly became saturated by all the stations in the central U.S. attempting to make that 100-point satellite contact, and we were unable to make any further contacts. We tried again the next morning when there was another favorable pass, but again encountered the saturation from everyone calling CQ and few stations (including us!) answering any CQ.
Lessons learned? Next time I will try to locate or design an alt-azimuth rotator that will improve our aiming. (It's hard to imagine how fast the satellite is moving when it passes right overhead!) And also, we will spend more time listening and answering other's CQ's, though that takes a bit more rapid tuning skills.
It was a great learning experience for me—which is what Field Day is all about! Thanks are due to W5NCD for the loan of the 2-m rig and antenna, and KB5SLI, KC5NT, and other enthusiastic HOTARC members for their antenna aiming and SSB listening skills.