[amsat-bb] Re: RAFT transponder turned on yet?

Bob Bruninga bruninga at usna.edu
Mon Apr 9 05:06:16 PDT 2007

> Do you have the Radar fence transponder turned on 
> this week? I will be in Texas this weekend and I 
> could listen for it if it's on.

Dan, Thanks,

The RAFT transponder needs to be activated by ground command when the satellite is approaching the radar fence.  Problem is, we have found only one station in Texas, New Mexico, Arizona, Arkansas, Mississippi, Alabama or Georgia that has volunteered to help out.  We have had some volunteers in other states, but they are too far from the radar fence beam.

What we need are OSCAR class stations on 2m that are familiar with normal packet that can logon to the remote sysop function of RAFT's onboard KPC3+ TNC and send the command to turn on the Radar Transponder.  It stays on for one minute and then fail-safe's to OFF. 

While the Radar Transponder is on, we get a Pure FM carrier that is also useful for hearing the "spin" of RAFT.  We have several volunteers in Europe and they confirm that RAFT is no longer spinning, but since the Radar Fence is only over the USA, that part of the experiment is still un-tested.

PE1ITR even built a 216.98 MHz beam and reports he can hear the 4 milliwatt RAFT radar transponder local oscillator.

The way it is supposed to work, is a station in the Southern USA turns on the RAFT transponder about 30 seconds before passing through the fence beam.  The 216.98 MHz receiver comes on and the 145.825 fm downlink comes up so we can hear anything the 216.98 receiver hears.  When it passes through the fence, everyone in the footprint should hear the 1 second or so radar beam as a Doppler tone.

>From The tone tells us the angle of passage through the beam, the time tells us when it crossed the beam.  From thos two, we can tell whre it is.

So, still looking for more volunteer 2m stations with beams familiiar with tracking satellites, familiar with operating packet, familiar with the KPC3 remote-sysop function, that live in those southern states from Arizona to Georgia.


More information about the AMSAT-BB mailing list