[amsat-bb] Re: Yes, DStar can work on LEO,

Dave hartzell hartzell at gmail.com
Mon Feb 26 09:57:26 PST 2007

Will this still work on an inverting transponder?

On 2/26/07, MM <ka1rrw at yahoo.com> wrote:
> The Icom IC-800 will work with some Doppler Error in
> Digital voice mode.
> I have been testing the IC-800 specifically to see how
> well it would work in theory with a 2-meter signal
> from a simulated LEO Orbit, such as ISS at 240 miles
> altitude.
> The results have been very promising on Earth.
> The IC-800 will decode good Digital voice, with a
> frequency error of > 2.5 kHz.
> And this was at an indicated signal level of S1 on the
> radios S-Meter.
> At higher S-Signal levels the amount of frequency
> error the IC-800 can tolerate in digital voice mode is
> higher.
> I setup a pair of IC-800 20 miles away.  Then by using
> a combination of 5k channels on one radio and 6.25k
> channels on the other radio, i was able to simulate 2,
> 2.5k and 3k channel doppler errors.  A beam antenna
> was used to Lower the indicated Signals levels until
> audio quality droped.
> The lower the altitude the higher the Doppler
> (Frequency dependant too).  The Doppler from ISS is
> approximately Plus and Minus 3.3 kHz.  This means that
> If a LEO satellite is approaching on 2-meters, the
> frequency you will see on your radio will be up to 3.3
> kHz higher for the first minute, then will quickly
> drop to zero Doppler for a few seconds at the 5 minute
> mark (assuming a 10 minute pass).
> So, in theory, if the Doppler on a transponder based
> satellite is less than 3 kHz and you have signals
> stronger than 1 S-Unit, it should be possible for
> 2-way Leo satellite via digital voice.  Anyone else
> have an IC-800 and want to test?
> Miles WF1F
> www.marexmg.org
> ka1rrw at yahoo.com
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