[aprssig] more ocean buoy stuff
Jim Lux
jimlux at earthlink.net
Tue Jan 9 17:59:10 EST 2007
Just following up on the many responses. Here's a quick summary:
1) VHF antenna sitting on the ocean surface is going to have "radio
horizon" issues (which I sort of expected). While there ARE
mountaintop digis around, they may have directional antennas, and
based on my experience in the Los Angeles area, you're going to need
a 50W Tx to get in halfway reliably.
2) 30m will require very good frequency control, and of course you're
subject to the vagaries of propagation. probably need to run a bit
of power too (but you'd have to do the same for VHF). (there may also
be a legal issue with control operators and the like.. one thing to
have a 30m APRS tracker in your car, where you can turn it
off. Totally another to have it drifting randomly off the coast of
California.. but that applies to ANY transmitter)
3) While the APRS format normally only includes lat/lon sorts of
things, there would be no problem adding some more data. After all,
it's just packet radio, and you can conceivably put pretty much
anything you want into the packet.
The commercial solutions are a bit more pricey (figure $1000 for the
Tx, and probably $500-1000 for a year's worth of monitoring) but are
intended for this kind of application, have very low power
transmitters (e.g. 401 MHz for Argos, with built in batteries,
designed to be glued to the back of a whale or something similar), etc.
Jim, W6RMK
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