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[aprssig] Base antennas and a couple other questions

Josh Keller jeepin95 at comcast.net
Sat Dec 11 01:42:00 UTC 2004


Seeing as how I am the most familiar with radios in my SAR group I have 
been assigned to come up with a few different things they want to 
purchase. I'm fairly new to all this radio stuff so I don't know a whole 
lot about it, which is why I'm asking here. Most of our searches are in 
the Columbia River Gorge and on Mt. Hood in Oregon. The terrain for 
those who don't know is fairly dense forest, 800' cliffs, plenty of 
vallys, etc. "Flat" isn't in our vocabulary.

There are 3 different things they are wanting to get setup, I'll start 
with what is probably the easier...

#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
KD7ZYW





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