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[aprssig] kayaks and aprs

jimlux jimlux at earthlink.net
Fri Aug 29 14:32:48 UTC 2008


> 
> Sounds like you're looking for AIS class B. (AIS class A is for commercial 
> shipping). Could be a bit bulky for a kayak, though, and APRS would be much 
> cheaper.

AIS Class B isn't available (legally) in the US.  The DSC/GPS marine 
radios from, e.g., Standard Horizon (aka Yaesu), are less than the cost 
of 2m ham rig + TNC, and waterproof and float to boot. (minimalist 
radios are $120, substantially fancier ones are $300+)

The Marine VHF radio also serves as a way to communicate with the other 
kayak, without having to have everyone have ham licenses (not that I'm 
not willing to have the rest of my family get their license, just so I 
can do an experiment). Not to mention that if you DO get into trouble, 
Ch16 is there.

But, the inexpensive marine radio is a pretty nice all-in-one package, 
and space/mass is at a premium on a kayak.



> From: Jan T. Pharo <la2bba at jpharo.net>
>>
>> is to get a marine VHF radio with DSC (which can send a GPS position) 
>> for the kayak, and set up a DSC receiver in the car, tied to a APRS 
>> transmitter.
> 
> You will probably have the same problem with the marine VHF (160 MHZ)
> as with your 145 MHz amateur equipment: same frequency (2m), same wave
> distribution properties.
> 
> The signals from a 5W handheld marine trx won't reach your car unless
> the 5W handheld amateur trx does the same.


The issue isn't reaching the car, it's that a regular APRS rig would 
have a tough time getting into the overall APRS system.  A 5W rig, in a 
car with an external antenna, driving 40 minutes across the LA basin, 
might only get 2 or 3 packets into "the system".   A combination of 
digis (N6EX?) that are up on very tall mountains with huge fields of 
view, and lots of 50W mobile rigs to compete with, and topography with 
lots of narrow ridges/canyons.


> 
> calls with position om marine channel 70 will probably reach the
> coastal station, but won't be retransmitted from there unless it's a
> distress signal (AFAIK from being a marine VHF user). So there might
> be practical issues in addition to the possible legal ones.

It would appear (I'll have to go down to West Marine or something to 
take a look) that some of the units have a "keep track of your fishing 
buddy" sort of feature, which presumably sends periodic polls/posits (on 
Ch70, I imagine, but without the "distress flag")...


> In the area you're talking about, is there a hilltop digi which cover
> the area where you will be navigating? In that case, your amateur APRS
> signals will be digied from there and reach (1) your car; (2) all APRS
> stations within hearing range of the digi, most probably also some
> Igate.

Nope.. no convenient hilltop digi.  Hence the idea to use the car as a 
"fill-in" digi to relay data from local area into the the wider net (the 
car, w/ more power and better antenna, is more likely to be able to get 
to a igated digi)

Just speculation at this point, in any case.




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