On Thu, Jun 28, 2007 at 03:20:11PM -0500, we recorded a bogon-computron collision of the <[EMAIL PROTECTED]> flavor, containing: > For a portable digipeater ..... > > *) Steel ammo-can. > $20 at Sportsmans Guide
We use waterproof high-impact plastic containers, not ammo cans. > *) Large gell-cell. > $190 for 55AH Optima Deep Cycle Marine > *) Mobile antenna mounted to the lid, perhaps a 1/2 wave antenna so > that it doesn't require a ground plane. > $45 We have several options, including a tripod-mounted mast, roll-up wire antennas, etc., chosen to fit the need. > *) 2-meter handheld radio. > $130 I'd probably go with a cheap mobile rig instead of a handheld. Doesn't need to be fancy, just something you can tune to 144.39 and wire up to the KPC-3+. Could be a used unit you get at a swapfest. By using something barebones you might find a perfectly servicable unit getting offloaded for cheap because it isn't sexy enough for today's standards. > *) Kantronics KPC-3+ TNC, set up to digipeat. > $180 Specifically, you would probably want it set to digipeat as a callsign substitution (MYALIAS) digi, with an alias of WIDE1-1 --- only because this is a nice generic fill-in digi alias, and folks wouldn't need specially programmed trackers to participate in on your missions. Once you have gotten set up to work with APRS well, you're going to want to start bringing your other agencies/teams into the fold, and having a standard set-up is A Good Thing. > *) Perhaps a chain to lock it to a tree in case a stray hiker finds > it during the mission. > Free!! (my garage supply house) > > System about $515 Might want to add in whatever is neccessary to guarantee that the gell cell is always fully charged. > Since the battery is 55 AH and the Kantronics list a 30ma draw that equals a > long time , Right? Not exactly right. The kantronics might only draw 30ma, but the radio will probably draw an amp or two while it transmits, and probably more than 30ma while receiving. It *should* be a low duty cycle, though, so it shouldn't be drawing that much that often. If you're using a handheld, you don't want to rely on its NiCd or NiMH battery, you want it powered off of the gell cell, too. > Given this..... what does this do for you? Where would you want it in > relationship to the radios in the field? A digipeater's purpose is to retransmit data from other stations. If you had good mountaintop digipeater infrastructure in your search area such that you could reliably get a digipeater to hear your teams, you don't need the portable digi. The assumption is that you either *don't* have a nearby mountaintop digi, or that there are significant gaps in its coverage right where you're most likely to be operating. The portable digi's purpose is to fill-in gaps in digipeater coverage so your field team's data can make it to the place where the data is needed. So you place it where it has a good view of the places where your teams will be working, and either a good view of the command post/base camp/whatever, or is in a good place where another digipeater can hear it well. Either way, your goal is to make sure that data from field teams get heard by the base station with the display --- either directly from the trackers, via a single hop through your portable digi, via a mountaintop digi, or via a chain including both your portable and mountaintop digi. Running trackers in the field that can't be heard by your base station display is pointless. The alternative that Curt's advocating (which I say again has yet to be proven, and is hard to do with readily available equipment) is to create an ad-hoc network of man-portable digipeaters on the theory that each field team should be within simplex range of some other field team, and that the whole collection of teams ultimately contains at least one who is in an area that can either be heard directly by base or by a high, wide (mountaintop?) digi. In both approaches you're trying to set up a network that boosts the range of an individual tracker so that it can get heard by the folks who need the information being produced. -- Tom Russo KM5VY SAR502 DM64ux http://www.swcp.com/~russo/ Tijeras, NM QRPL#1592 K2#398 SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM "And, isn't sanity really just a one-trick pony anyway? I mean all you get is one trick, rational thinking, but when you're good and crazy, oooh, oooh, oooh, the sky is the limit!" --- The Tick _______________________________________________ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
