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[aprssig] more ocean buoy stuff

Jim Lux jimlux at earthlink.net
Tue Jan 9 22:59:10 UTC 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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