On Nov 19, 2004, at 4:57 AM, Josh Keller wrote:
> My Search & Rescue unit has a couple of Motorola CDM-1250 mobile
> radios that I've been asked to turn into a link repeater. One
Two comments Josh, from long experience with SAR groups.
a) Mobile rigs do not make properly built repeaters. SAR = Someone's
life is on the line. Don't do this. If a couple of mobiles and a
lashed-together RICK in a beat up plastic box are what your field teams
are relying on - they'd at least better know that. Tell them your
little "repeater" is barely better than a toy before they call for help
through it.
(I'm sorry to be harsh, but read below for more of the reasoning why.)
b) Rarely is a SAR group in an area long enough to deploy a portable
repeater in any fashion where a couple of people with 50W mobiles and
good antennas can't handle the communications needed. And you lose the
risk and liability exposure of #a above.
And I guess a third comment:
c) If this is for a permanent repeater link - using mobiles and RICK is
even worse than #a. Just don't do it. Everyone knows budgets are
tight, but watching a mobile melt down right when the furball really
gets flying on a bad day in the SAR biz that's your only link
transmitter will make you a believer in "do it right the first time, or
tell the boss he needs to pony up a budget that works". Yes I know you
can turn the power back - if it's a properly engineered system with
plenty of link-fade margin and good antennas and you can do it with a
mobile, fine... but if not and it needs to be a 10-30W link... buy
radios designed for the backbone.
That's my thoughts on SAR repeaters. Good luck with it if you really
need the portable box. I understand there are useful purposes for
them, but I can't stand it when I see a couple of mobiles lashed
together in a temporary box and it's supposed to be my primary way to
reach help from the back-country. NO THANKS.
I know I'm making a lot of assumptions here, but I see bad engineering
far too often on radio lash-ups that are supposedly carrying primary
health and welfare traffic. Not a good thing to have your name on, if
you're the designer/technician. It's a good way to accidentally test
out how good your liability insurance is after someone's hurt.
Sometimes quick lash-ups last for years and years on a hill somewhere
and people get used to them and start planning on them being there.
They do their risk analysis of who to send searching in a particular
area (by themselves? not by themselves? etc.) by what they BELIEVE to
be the communications capabilities from that location -- and five years
down the road no one remembers that the silly thing is a couple of
cheap mobiles lashed together in a box with a car battery... they just
figure it's a full-blown repeater. No matter how many times you tell
them otherwise.
For hams... sure, slap stuff together. For SAR -- no. Not worth the
headache or possible problems...
Nate WY0X
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