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Re: ISS Repeater






> From: bruninga@usna.edu
> Subject: Re: [amsat-bb] Re: ISS Repeater
> To: Kenneth.G.Ransom@nasa.gov; ko6th_greg@hotmail.com; w5ggw@wonderly.org
> CC: amsat-bb@amsat.org
> Date: Tue, 30 Dec 2008 22:09:02 -0500
> 
> > The ISS radio system currently supports 
> > only one mode at a time. The current 
> > L/v configuration is scheduled to be 
> > active until Saturday, Jan 3.
> > 
> > And I don't think you can't get into 
> > the 1.2 GHz uplink without a yagi ;)
> 
> The most important thing is proper Doppler compensation.  At 1.2 ghz the Doppler is from -25 KHz to plus 25 KHz or so, and you have to be within a few KHz, or your splatter will not open the squelch of the repeater.
> 
> With 11 full Doppler steps during a pass, you have to nail it exactly or you dont get through he 12.5 KHz filter.  Plus I bet even being 2.5 KHz off between each step and speaking fully, will splatter so much as to keep the squelch closed.
> 
> So in that case, there are 22 discrete windows of opportunity, only half of which are useable, so it takes real care to get through.  Of course, I am only kibitzing, since I have not tried it, but all the signals I have heard  do NOT seem to be suffering power limitation, but all seem to be suffering off-frequency splatter and therefore squelch unreliability.
> 
> Maybe setting narrow band deviation (as used in europe) will reduce the spaltter and keep the squelch open better.
> 
> Good luck!
> Bob, WB4APR
> 
> I'd suggest setting narroband deviation too, to help prevent


Yeah, I think it's going to be one hand on the mike and the other on the uplink tuning knob, adjusting it real-time by ear.  I can use the computer to keep the antennas and downlink radio on track, but the rest is going to be up to me.

Greg  KO6TH





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