[aprssig] Base antennas and a couple other questions

scott at opentrac.org scott at opentrac.org
Fri Dec 10 20:08:55 CST 2004

This might not help you any, but I've got a working prototype of a TK-790
specific variant of the OpenTracker installed in one of our vehicles.  It's
a transmit-only tracker though, and won't be of much use as a base station.

We've got everything pretty much permanently installed in a mobile command
post.  Antennas aren't really my thing.  As soon as I get my uTNC, I'll be
setting up an APRS demo using the existing radios and laptop.  DMAPPER
doesn't support AGWPE or I'd use that.  I'm considering building an ammo can
digi, too - another uTNC could fill that role until my own project is

Is your SAR team part of the Mountain Rescue Association?

N1VG / 31-Rescue-35

-----Original Message-----
From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Josh Keller
Sent: Friday, December 10, 2004 5:42 PM
Subject: [aprssig] Base antennas and a couple other questions

#1) We were given a Kenwood TK-790/890 110W VHF/UHF radio for use as a
base station. For this my task is to get an antenna. The requirements
here are that it needs to be relativly portable as it will be packed
away in a trailer after each mission. It should be relativly easy to
setup so that almost anyone can throw it up in the air. It also needs to
be omnidirectional. Our primary frequency is Oregon State SAR 155.805Mhz FM.

#2) We have a few Kenwood D7-AG units and a couple D700 units. One of
the D700s wll be connected to a laptop to track teams via APRS. At the
moment I have a home built j-pole in use for this...is that the best
route, or is something commercial (<$200) going to work out better?
Again...simply to setup, relativly portable, etc. This will be
monitoring 144.390 99% of the time, seldom will it TX.

#3) They also would like a link repeater setup so that when 'base" needs
to be setup in a non-idea radio location we can put a repeater in a
better location which will link down to base on a separate frequency. We
have found a plastic ammo can style box to place 2 Motorola Radius M1225
units in. The idea was to put 2 SO-259 bulkhead mounts through the ammo
can, along with a powerpole connections for power. In addition an
extender module either from Echo Communications or a Motorola RICK will
be included in the box.

Most of  the time this box will actually be used in base as 2 separate
radios. The ability needs to be there though to create a link repeater.
Again, the question is going to be on antennas. I'm guessing it would be
best to use the same antenna as from question #1 above for simplicity
since they will be working in the same frequency range.

The other question is if it would be better to go with a regular metal
ammo can. Would this providide RF shielding for the radios? Is that
important? Would having 2 bulkhead mounts drilled through the metal box
cause problems?

Although coming up with a true repeater would probably be idea, that
isn't in the cards at this point. The powers that be would like the
above listed setup, so thats what I'm out looking for.

Thank you for any info you can provide.
Josh Keller

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