[Xastir] More system questions

[Curt, WE7U]

On Thu, 28 Jun 2007, Tom Russo wrote:

> We use waterproof high-impact plastic containers, not ammo cans.
>
> >  *) 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.

Or a used handheld.  If using a mobile rig, you can often disable
the backlight on the radio, saving quite a bit of power.  This might
involve clipping a wire/removing a component/cutting a trace.


> 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.

Another reason for a handheld:  Lower current consumption.  At least
if you pick the right one.  Also, it's advisable to run the handheld
with the squelch open (the audio out is always making noise whether
there's a signal or not) and have the TNC in a mode that'll work
with this.  This will allow you to both hear weaker signals and to
pick up signals where the transmit delay on the sender is set very
short.  Also it removes one more possible source of making the unit
non-functional:  Having the squelch set incorrectly...  You can
open the squelch up all the way, set the audio level appropriately
for good decoding, then somehow fix those two controls so that they
don't get bumped.  Fingernail polish to fix them in position
perhaps.

So:  With a handheld you can use lower current, allowing the battery
to be sized smaller, allowing the box to be smaller, allowing the
whole thing to weigh less.  Or:  Allowing you to have a much longer
run-time.


> 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.

Yep.  Yet to be proven.  I put forth that eventually this will be
the way we'll want to operate in the field, but for now, Tom is
proposing the tried-and-true approach which makes good sense.

With the experimental approach, the goal is also to get the position
data for each team and base onto every team's GPS map screen, as
well as provide for some sort of two-way communication, however
rudimentary.  For instance base could put a "recall" object onto the
map just ahead of a team that it wants to recall but can't reach on
the voice radio.  The team could place an object nearby called "ACK"
for acknowledged, which base would then see.

--
Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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"Windows:  Microsoft's tax on computer illiterates." -- WE7U
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