[amsat-bb] Duchifat1 updates
Herzliya Science Center
4x4hsc at gmail.com
Fri Jul 17 10:53:16 UTC 2015
Duchifat1, launched 1 year ago, was supposed to have onboard a "standard"
space APRS transceiver operating on 145.825MHz. That would have made the
satellite compatible with ISS, other APRS satellites and APRS-IS.
Unfortunately, a short time before launch, we realized that technically we
couldn't keep the intended 145.825MHz transceiver in the final satellite
configuration but we still wanted to make some contribution to amateur
radio in space. After a quick research we discovered that the 2nd
transceiver onboard Duchifat1, the ISIS (Netherlands) TRXUV planned for
Duchifat1's command and telemetry can be programmed to also accept APRS
packets!, however, limited to 14 characters long. Also, the
downlink digital modulation was not the common space APRS of 1200bd AFSK
but 1200bd BPSK, and the uplink frequency is in the UHF band.
We therefore came with the idea of supporting COMPRESSED APRS, and instead
of the standard digipeater, we implement kind of "store&forward" function
in which the satellite collects packets during its flight in orbit and the
students of Herzliya Science Center will download those packets and display
them on a world map in a web site programmed by them.
We published here a few weeks ago the opening of this service and put in
our web site detailed instructions on how to use the Byonics TinyTrak4
(TT4) tracker, with or without GPS to generate packets in the required
format that Duchifat1 will accept. So far, TWO pioneers used this service.
THANKS PETER & MIKE!
While the TT4 solution is still the best we know for sending your actual
live position to Duchifat1, we are happy to announce the 'APRS Encoder', a
new tool in our web site that can generate for you the COMPRESSED APRS
packet for Duchifat1.
The input for the new APRS Encoder is the station's (or nearby) coordinates
set that can be obtained from Google Maps, so this solution is naturally
adequate for stationary base stations, while mobile stations should still
use the Byonics TT4.
The output of the APRS Encoder is a 14 character long Compressed APRS
packet that can be converted to 1200bd AFSK with a hardware TNC or software
like MIXW – just copy the 14 chars string and paste it into the MIXW window.
The MIXW should be set to mode Packet, using the most common "VHF 1200 baud
(Standard 1200/2200Hz)" setting. Prior registration is required.
All the details on the satellite, the registration and the APRS Encoder are
at this link: www.h-space-lab.org
Please read all the documentation in the site.
We wish you all good luck and enjoy!
73 from 4X4HSC team: instructors 4Z1WS and 4X1DG, and the students!
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