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[aprssig] Re: Radio Recommendation

Curt, WE7U archer at eskimo.com
Mon Jul 19 16:37:06 UTC 2004


On Mon, 19 Jul 2004, Sean Jewett wrote:

> On Fri, 16 Jul 2004, Keith - VE7GDH wrote:
>
> > Another option... the PocketTracker also from www.byonics.com. Only
> > about 250 mW, but it's a complete APRS tracker when you add the GPS. It
> > can run 100 hours on a built-in 9V battery, or it can be powered from
> > 12V. Just don't go adding an amplifier to this setup. A gain antenna?
> > Perhaps if you are away from populated centres that have lots of digis
> > or IGATEs.
>
> I'm not sure I'm following you on your comment about not adding an amp.
> Care to expand or clarify?

Because it only has a transmitter and no receiver, it can't listen
on the channel before transmitting.  Because it is low power, it has
little chance of overriding another transmitter on frequency.  The
FM capture effect causes those with higher received strength to be
decoded (assuming the strength is sufficiently higher than the
others).  The lower-power units need to be very close to the
receiving station or must be transmitting when the channel is clear
to be heard.

If you were to crank up its power you would end up interfering more
with other transmitters on frequency, at least if you keep it on
144.39.

If you instead switch to a different frequency and run these units
with higher power, most likely with timeslots enabled for each, then
I don't see a big problem with it.

Personally I'd like to see a higher power version of this thing
produced, but we'd be using it for SAR applications, off in the
woods/mountainous country.  We'd have little chance of interfering
with others, but if we did we could move to another frequency for
our "events".  We're still evaluating them in our area to see
whether more power might be necessary.

--
Curt, WE7U			         http://www.eskimo.com/~archer
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"




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