Gentlemen,
Please do not use FM on any of the transponder satellites, whether D-Star or plain FM. FM of any kind is expressly unwelcome on AO-7 especially.
If you would like to set up a test of D-Star via AO-51, please organize the effort and send a request to schedule it to [email protected] or to myself directly and we will accommodate the test on a FM satellite, where FM belongs. I think it'd be an interesting experiment.
73, Drew KO4MA AMSAT-NA VP Ops
----- Original Message ----- From: "MM" [email protected] To: "Dave hartzell" [email protected]; "Amsat BB" [email protected] Sent: Monday, February 26, 2007 4:18 PM Subject: [amsat-bb] Re: Yes, DStar can work on LEO,
In my first memo about Digital Audio on Satellites I did not have time to go over a few other outstanding issues, such as Inverting Transponders and Doppler on the 440 band.
Will DV work on Inverting Transponders? I do not know. My guess is that Non-inverting would work better, but that's just a guess. Let's try it and find out.
Doppler on 440. The Doppler on 440 is plus and minus 10 kHz. That is too much for the ID-800 and similar radios running digital audio. Normal FM 5k deviation voice can work find at 3 kHz frequency error and is even usable with noise up to 6 kHz of frequency error. Digital Voice would work best on 10 meter / 2 meter satellites, with non-inverting transponders. Maybe AO-7 could work. The other satellite VUSat-OSCAR 52 is inverting.
Future Radios: Wish List Most mobile radios made today are designed for channel steps starting at 5 kHz, 6.25, etc. It would be desirable if manufactures would design their rigs for smaller channels steps to allow us a little more flexibility in using them for FM satellites. It would not add much cost to a typical FM mobile rig to allow 1.0 kHz and 2.5 kHz channel steps. For FM satellites you do not need to be exactly on frequency. You just need to be in the ball park (plus and minus 2.5 kHz works).
Miles --- Dave hartzell [email protected] wrote:
Will this still work on an inverting transponder?
On 2/26/07, MM [email protected] 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
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At 09:14 AM 2/27/2007, Andrew Glasbrenner wrote:
Gentlemen,
Please do not use FM on any of the transponder satellites, whether D-Star or plain FM. FM of any kind is expressly unwelcome on AO-7 especially.
If you would like to set up a test of D-Star via AO-51, please organize the effort and send a request to schedule it to [email protected] or to myself directly and we will accommodate the test on a FM satellite, where FM belongs. I think it'd be an interesting experiment.
Umm, I thought D-Star was a digital mode, not riding on top of FM. Is it transmitted as AFSK or is it modulated directly onto the carrier? If it's the latter, then it wouldn't work on an FM satellite.
73 de VK3JED http://vkradio.com
It's GMSK modulation. I don't have the spec in front of me but I doubt it'll run where there is any processing (preemphasis/deemphasis) is taking place. This is why I suggested using a linear transponder. I realize that D-star equipment would be unfriendly to the current operations of sats being that there is no continuous tuning D-Star radio currently so using this would most certainly would drift into other QSO's in progress. Along with that problem you have the inability to full duplex the QSO because someone mentioned that the vocoder/decoder can be used only in one direction at a time. Seeing as this is a new mode and the equipment is expensive, I don't see this being wildly popular that it'll "take over" the sats from their usual operation. A test at some point in the future would probably be good to see if it can be done. Perhaps Echo's B-side could be converted to pass GMSK modulation? Something for the programmers to think about.
73 de Pat --- KA9SCF. Amsat #35741
On 2/26/07, Tony Langdon [email protected] wrote:
At 09:14 AM 2/27/2007, Andrew Glasbrenner wrote:
Gentlemen,
Please do not use FM on any of the transponder satellites, whether D-Star
or
plain FM. FM of any kind is expressly unwelcome on AO-7 especially.
If you would like to set up a test of D-Star via AO-51, please organize
the
effort and send a request to schedule it to [email protected] or to myself directly and we will accommodate the test on a FM satellite, where
FM
belongs. I think it'd be an interesting experiment.
Umm, I thought D-Star was a digital mode, not riding on top of FM. Is it transmitted as AFSK or is it modulated directly onto the carrier? If it's the latter, then it wouldn't work on an FM satellite.
73 de VK3JED http://vkradio.com
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
It might make more sense to use a different modulation technique for satellite links, and establish earth statiions that gate D-star packets over the links. They're apparently Ethernet frames inside a D-star wrapper; the docs show a pretty elaborate routing scheme.
-- 73 de Maggie K3XS Editor, Phil-Mont Mobile Radio Club Blurb - http://www.phil-mont.org Elecraft K2 #1641 -- AOPA 925383 -- ARRL 39280
participants (4)
-
Andrew Glasbrenner -
Margaret Leber -
Patrick Green -
Tony Langdon