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SUNSAT HT success!



SUNSAT 1200 baud Mode-B SUCCESS with an HT!

After last nights failure to get any 9600 packets digipeated from a 5W HT
with WHIP antenna, in mode B, I decided to give in and try 1200 baud this
morning (5:45 AM!) to pick up the other 7 dB.... SUCCESS!

Yes it can be done with BEAMS and more power, but that is not the
objective here. We are trying to develop an APRS satellite comm system
that can communicate to and from HT's with WHIP antennas IN YOUR POCKET
and mobiles.

SUNSAT has demonstrated that ModeB can deliver MESSAGES to your HT in your
pocket and even indoors! ... and that MODE-J can reliably receive MESSAGES
from an HT with whip antenna in your hand.  (IE, what ever link is on 2m
has a 9 dB advantage over UHF and 1200 baud adds another 7 dB).

Fortunately SUNSAT (and APRSat) is leading up to a 2m up-and-down straight
DIGIpeater mode, but since that would invite bedlam, we are cautiously
testing each link separately with the MODE-J and MODE-B tests...

THis is the basis for our APRSat design.  It will have 2m up-and-down for
5W HT's only.  Mobiles with 50 watts will be strongly encouraged to use
9600 baud on UHF where their added power can make up for the 10 dB worse
path loss.. Also, this avoids ANY collisions with the HT's.  Its the best
of both worlds:

MODE-B: DOWNLINK is STRONG and requires NO TUNING. (Unattended)
        Uplink Needs 9 dB more and requires tuning Doppler BLIND

 *   5 W HT whip 1200 Baud UP  (tracking or traveler message uplink)
 *       HT whip 9600 baud reception anywhere anytime  (great demos)
 *   5 W HT portable ARROW 9600 baud UP and DOWN.  THD7(g) only
 *  50 W Mobile 9600 baud both ways 
 *  Any station IGates with unattended no-tune, OMNI horizon-to-horizon
    coverage.  (Only need one every 1000 miles). ANYONE with a D700
    and 50' of coax and a whip antenna can do it...

MODE-J:  Easy 5W uplink, NO TUNING required.  (Unattended)
         Omni downlink receive of central 30% of pass.  Needs tuning
 
 *   5 W HT whip 9600 baud UP (sending your message out)
 *  50 W Mobile 9600 baud both ways
 *       HT/Mobile reception with WHIP during central 30% of pass

In both cases, 1200 baud works 7 dB better than 9600...

So, Here is what you can do NOW with SUNSAT in MODE-B 145.825 down 9600
baud and  uplink 436.290 (-/+ 10Khz doppler) 9600 OR 1200 baud.

1)  Transmit 1200 baud with ANY system with 5W or more and omni antenna
                    (but you must anticipate the -/+10 KHz of doppler)

2)  Receive with ANY 9600 baud system (THD7  any model with a laptop)
                                      (THD7g or D700 to front panel)

3)  Receive packets by TELNETing to www.aprs.net or 
    Look at MAP at www.aprs.net with any browser for your position.

Or if you know anyone's call that is uplinking to SUNSAT, go to FINDU.COM
this site to see them:

   http://map.findu.com/wb4apr

This site shows you were ANY aprs station is REAL TIME if they have been
heard anywhere on the planet within the last few hours.  FOr SUNSAT, it
assumes that someone in your country is feeding the NO-TUNE, HORIZON TO
HORIZON downlink on 145.825 into APRServe (www.aprs.net).

See ya on the bird..  Remember, anyone with a 1200 baud TNC and a UHF FM
radio can uplink!  You can HEAR it digipeat the 9600 baud burst back
down..

de WB4APR, Bob


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