Tuesday, October 19, 2010

Ham Radio Satellite Observations and Tips!

In no particular order, here is a list of the ham radio satellites that I have used so far. There's definitely a learning curve for using each satellite, and I've tried to add as much of the useful information as I can remember! Just FYI, the full rig setup is described in an earlier post, but to summarize I work portable with twin FT-817ND QRP radios and an Elk log-periodic dual-band antenna, for full-duplex operation on all of the linear and FM satellites.

AO-51: FM (2m up, 70cm down)
A fun satellite to work, easy to do with even a handheld. It's possible to work this bird with a rubber duck! There is no set daily schedule of operations, however the control team will change the uplink/downlink configuration periodically for a few days at a time. Often very crowded during weekends and during passes over central North America. From here in the west coast, ocean passes (west) are often fairly quiet, with just two to five hams on. Often hear Hawaii and Alaska from here in California. 5W into a directional antenna works great. Polarization stays pretty constant until mid-pass then seems to flip 30 to 90 degrees. The bird is sun-synchronous so there are good passes at start and end of day - the western passes at the end of the day are accompanied by a nice sunset. Often requires a CTCSS tone. The latest updates for AO-51 are located here.

SO-50: FM (2m up, 70cm down)
Less traffic than AO-51. No pre-set schedule, seems to use the same mode day-in and day-out. Also easy to work with 5W and a directional antenna. One quirk is that this bird seems to spontaneously change downlink frequency: I have recently seen it appear 10 kHz below published, and sometimes 5 kHz below. When this happens, it appears to be gone entirely (if using computer tuning) unless you switch to manual adjustment. You can overcome this by having multiple instances of the nominal downlink frequency in your control software. Requires a CTCSS tone to activate it (stays on for 10 minutes), and a separate CTCSS tone for uplink TX. Since this bird is not exactly sun-synchronous, there are some nice passes during the day, as well as nighttime passes.

AO-27: FM (2m up, 70cm down)
Fairly busy during passes. This satellite has scheduled operations, and is typically turned on as it comes over North America in afternoon passes. Fairly easy to work. There aren't any real quirks with this one, other than to be prepared for it to either not be there (if not turned on) or to suddenly turn off part way through the pass.

HO-68: FM/Linear (2m up, 70cm down)
This bird is often very crowded during weekend passes when in FM mode! This satellite is also scheduled, sometimes it's off, sometimes on, sometimes in FM, and sometimes in linear transponder (SSB) mode. The website www.camsat.cn usually has the current schedule for activation, and the satellite is often turned on for daylight passes over North America. If nothing is heard on FM when the satellite is expected to be active, check SSB because it's probably in linear transponder mode. The FM repeater also relays packets. so there are quite a few packet bursts during a typical pass. Requires a CTCSS tone. Seems to have a bit larger footprint than the other FM birds. This satellite often "ignores" uplink transmissions, for example, you can TX once, hear nothing on the downlink, then TX a few seconds later and hear yourself full quieting. This bird also seems to be "tumbling", in that the downlink polarization changes about every 30 seconds or so -- so handheld antenna polarization control is especially helpful. The latest updates for HO-68 are located here.

FO-29 Linear/SSB (2m up, 70cm down)
This linear transponder sat has a 2m uplink and 70cm downlink, and had a pretty much sun-synchronous shedule with morining and evening passes. However, as of mid-October, the power budget on the sat forced the operators to turn the unit off entirely, and then the bird failed to respond to any command signals. Currently it's silent. 5W and a directional antenna was plenty to work this one. We'll see if it comes back to life.

VO-52: Linear/SSB (70cm up, 2m down)
This one is 70cm uplink and 2m downlink, and makes some nice mid-morning and early-evening passes. The mid-morning passes usually have one or two conversations on them, while the evening passes (9pm local time, 0400UTC) are virtually devoid of anyone else! I find this to be a good sat for testing my radios with uplink/downlink calibration, etc -- even though I just talk to myself (call CQ) on this bird on the evening passes, it's still handy to make sure everything's working well. It's also good for practicing aiming the antennas, optimizing polarization, etc. The bird is fairly sensitive and quiet. Works well with 5W and a directional antenna.

AO-07: Linear/SSB (70cm up, 2m down)
This is the satellite that went "dead" many years ago with shorted batteries, then came "back to life" after the short went open-circuit. Since there are no functional batteries, the bird is only active in sunlight (which right now, given its orbit, is 24 hours a day), and switches between Mode A (2m up, 10m down) and Mode B (70cm up, 2m down) every 24 hours (currently around 0000 UTC). The oscar.dcarr.org website is a good one to check for the current mode. Since AO-07 is in a much higher orbit than any of the other satellites listed here, it has a much larger footprint. One thing I've found is that AO-07 seems to "disappear" on passes that go nearly directly overhead; this might be because when looking up underneath the sat, the antennas may not be oriented for best reception of my QRP signal with the small log-periodic. I haven't tried Mode A, but on Mode B, I've made some nice contacts out to 3000-mile range (maybe 15 degrees elevation).

Key Resources:
Real-time satellite status: oscar.dcarr.org
The AMSAT site: www.amsat.org

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