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Re: Future ISS amateur radio modes, Marex



Hi Eric:

I agree with your analyses on the Doppler / PL Tone
shift.
With a Doppler of less than 2 kHz, the PL tone should
be passed with little or no degradation. The FM
Capture effect locks on to the signal and compensates
for some of the frequency error.  At a higher Doppler
values, you do see noise and other distortions begin
to creep in.
The PL tone suggestion just needs to be tested to get
a realist feel on what to expect.  We have had issues
in the past, with putting stuff in space that was not
properly tested end to end.  Whenever I hear of a good
idea, I try thinking about the environment where it
will be used.  

Packet is affected by Doppler when it begins to get
above 2.0 kHz.  The amount of error is also dependent
on the Signal level at the receiver.  At a signal
level of S9 and a 2.5 kHz Doppler you will see very
few data errors (Retries caused by check sum errors). 
At S2 and 2.5 kHz Doppler your receiver will have a
harder time decoding the data.  Thatís why, at the
beginning and End of ISS packet passes when the
Doppler is the greatest, I adjust my TX and RX for
Doppler.

On a related note, I did test the Icom ID-800 digital
voice mode with a Simulated Doppler.  The results were
very good.  The ID-800 uses a 2.4 kbit digital data
stream for Digital Audio.  When this data stream was
subjected to simulated Doppler of 2.5 kHz, at an
indicated receiver S-meter level of S1, the audio
stream decoded perfectly.  This means that some of the
narrow digital modes can be used from FM satellites
when the Doppler is less than 3 kHz (depending on
received signal strength).

Miles WF1F


--- Eric van de Weyer <eric@van-de-weyer.org> wrote:

> Hi Miles, 
> 
> think about it, the percentage shift of the carrier
> frequency of the
> modulating tone compared to the carrier will be
> negligible and therefore the
> effect on the tone itself will also be virtually
> zero. If the Doppler
> affected it significantly, our voices through the
> system would also be
> changed significantly. Also, packet wouldn't work
> either and we know that it
> works fine. 
> 
> 73....Eric VK2VE.
> 
> -----Original Message-----
> From: sarex-bounces@AMSAT.Org
> [mailto:sarex-bounces@AMSAT.Org] On Behalf Of
> MM
> Sent: Wednesday, 2 May 2007 22:42
> To: va7to@yahoo.ca; sarex@AMSAT.Org
> Subject: [sarex] Future ISS amateur radio modes,
> Marex
> 
> ISS Amateur Radio Status: May 2, 2007
> 
> Future Projects on ISS
> By Miles Mann WF1F,
> 
> MAREX-MG News	www.marexmg.org
> 
> Manned Amateur Radio Experiment
> 
> Future Projects on ISS:
> 
> There are a lot of good ideas regarding how to use
> Amateur Radio equipment on board ISS.  I like the
> suggestion from Darrell Bellerive va7to of using a
> Downlink PL tone from ISS for the voice channel.
> 
> I am not sure how much the Doppler will affect the
> PL
> tone.  I am intrigued by the idea and will try some
> terrestrial experimentation to if there is much of
> an
> effect.
> 
> Current In-flight projects on ISS include:
> Packet, Voice (mono-band), Cross-Band Repeater and
> SSTV.
> 
> Each of these projects has shown good results from
> manned platforms such as Mir and ISS.  The projects
> that the space agencies like the best are the ones
> that do not use very much crew time.  The projects
> Packet, Cross-Band and SSTV are the highest bang for
> the buck projects because they do not take up too
> much
> crew time. And as we know, free crew time for ham
> projexts is very very limited.
> 
> Cross-Band Repeater generates a lot if good interest
> from the amateur radio community.  There are a few
> down side issues to cross band that have to be taken
> into consideration.
> Not all countries allow amateur radio on the 440
> band
> (sometimes called 70cm).  
> There is more Doppler on 440 (+ and - 10khz)
> Some of these and other issues can be overcome with
> experience.
> I wold be nice if someone could design a small
> frequency agile cross repeater that could work on
> any
> combination of 10 meter, 2-meter and 440.  That way
> we
> would have the maximum flexibility based on project
> needs.  We have the existing antennas on ISS, let's
> use them.
> 
> Existing ISS Antenna counts:
> Module FGB 	One Sirius 2-meter antenna tuned for
> approximately 147 MHZ.  Dual one-quarter wave
> co-phased antennas mounted externally.  Currently
> connected to the Ericsson Ht.
> 
> Service Module, Three Tri-Band antennas, that
> support
> 2-meters, 440 and a patch antenna supporting 1.2 -
> 2.4
> GHz.  (The patch antenna has high coax losses,  > 8
> dB
> at 1.2 GHz)
> One 10-meter whip and 1.2-2.4 GHz patch combination.
> One of these Tri-Band antennas is conneced to the
> D700.  The others are not currenlty used.
> 
> Grand total of currently installed Amateur Radio
> antennas on ISS
> 4 antennas for 2-meters
> 3 antennas for 440
> 4 antennas for 1.2-2.4 GHz
> 1 antenna for 10 meters
> 
> MAREX is focusing on the entry-level projects for
> beginners such as Slow Scan TV and Packet Email.  We
> have had excellent results on Mir project with both
> SSTV and Packet.  And last summer experimented with
> SSTV from ISS with some very good down linked
> images.
> 
> The long term plans, hardware and crew time
> permitting
> is to place SSTV on a 10 meter down link,
> continuously
> streaming images from ISS.
>
http://www.marexmg.org/imagessstv/SpaceCamImages1.htm
> 
> And place a continuous presence Packet Email system
> on
> 2-meters, running 24/7.  MAREX has received initial
> approval to use a Kantronics KPC-9612 TNC as the
> data
> engine.  This modem supports all the standard
> features
> of most TNC's built, including:
> Full Multiple user simultaneous Email users.
> Simultaneous dual speed support 1200 and 9600 baud.
> Un-proto modes, Text messaging and APRS beacons.
> 
> Some unapproved projects Marex is working on are to
> provide a full plug and play solution for a new
> system.  New style easy to use transceivers, Analog
> and digital voice capabilities, Bolt on heat sinks
> and
> fans to compensate for zero gravity cooling issues,
> standardized plug in DC headsets and more.  
> Your support for these projects would be greatly
> appreciated.
> http://www.marexmg.org/
> 
> 
> 
> ARISS Web page and other great Space projects
> http://www.rac.ca/ariss/
> 
> 73 Miles WF1F MAREX-MG
> 
> Until we meet again
> 
> DOSVIDANIYA Miles WF1F
> 
> 
> 
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> Sent via sarex@amsat.org. Opinions expressed are
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> 


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