[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Amateur Satellites (definition?)



You may be interested in a project that I began over a year ago to build a
GPS tracking ocean-going buoy for tracking oil spills (in Cook Inlet,
Alaska) for my company.  Previously we had some units that used continuous
VHF beacons that required DF tracking.  They were marginal in use because
of the limited RF output power (~50mw) which was a constraint of the
on-board batteries.  Often we had visual sighting of the units before
picking up the weak VHF signal.  These units cost us $750 per buoy.  The
tracking receivers cost $5000.

In summer 1999 I propose to management that inexpensive GPS trackers could
be built at a fraction being asked by the commercial manufacturers (~
$5,000).  Also commercial tracking/mapping software was prohibitively
expensive for our small company (upwards of $30,000).  The first prototype
was built for about $800 of materials.  The commercial APRS license is $495.

Of course, as a ham I thought of using TNC's, GPS units, and APRS.  The
prototype was built in 2000 and tested last year.  It consisted of a
PicoPacket TNC, Garmin GPS-35, and a Ritron DTX-150 5w transceiver (we had
used this radio successfully before in custom-made portable repeaters).
The original unit was crudely housed in a 12-inch section of 6-inch
diameter plastic drain-pipe with threaded end-caps.  A 19-inch brass tube
antenna was used with a small loading coil.  The unit was programmable to
beacon anywhere from every 10 seconds to once/hour.  It was powered with a
2 AH gel-cell battery and two Lithium batteries which gave a life of 72
hours beaconing every 10 minutes or more.

A land-based test was made tracking the unit out to about 12 miles where
terrain and foliage permitted good propagation.  A sea-trial was conducted
last fall with good data achievable to 7 miles, receiving using a
ship-mounted unity-gain whip antenna, commercial mobile VHF radio, KPC-3,
and a laptop.  Operation is on a non-amateur VHF frequency.

>From our experience with the prototype, seven units will be constructed
this year.  They will use a completely custom-made aluminum water-tight
enclosure that can withstand ice crushing and abrasion by sea ice (we
hope).  Lithium batteries were found inadequate and only gel-cell
rechargeable batteries will be used.  The new model will use the Garmin
GPS-36 Marine unit and the TNC will be replaced by the MIM made by Bob
Bruninga.  This will result in lower battery drain with the a deployment
life expected up to 7 days.  Another advantage of the MIM module will be
remote monitoring of battery voltage and hull (water) temperature.

Ultimately, a ship outfitted with a 40w VHF radio and TNC will act as a
digipeater to relay the beacons from the buoys back to land.  The
digipeater will also be interconnected to the ships GPS to provide GPS
tracking of the ship.  Eventually I hope that this will lead to GPS
tracking of all the companies oil spill recovery vessels and provide
shipboard packet communications with the command center.  This will
facilitate oil spill recovery operations with near real-time information,
tracking the movement of the spill using the buoys and providing positions
of the recovery vessels.  The APRS map display will be networked to all
work stations at the response center and displayed on an overhead screen in
the command center using a projection unit.

Ed
Chief Comm Tech, Cook Inlet Spill Prevention & Response, Inc.
Nikiski, Alaska



----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home