This is version 2 of the N8WKM 902 Repeater operating at
927.2625Mhz Output and 902.2625 Mhz Input. The repeater
requires 131.8 Tone for access. As the repeater says, "Welcome
to the N8WKM Repeater. The time is ...."
The repeater was started with an idea after spending some time talking
to other hams who were already using the 902-928Mhz band during
the Dayton Hamvention 2002. Several
people got excited about using 900Mhz and so began the the first 902Mhz
amateur repeater in West Michigan.
David Buffington KC8HVT and I were the first to take the plunge that very
Sunday afternoon by purchasing a pair of Motorola MTX-9000 portable radios.
Within a couple of weeks several of the local hams were beginning to find and
purchase suitable radios to use on 900Mhz. During this time I purchased a couple
of Motorola MaxTrac 900 Radios and began the learning curve to make these radios
operate within the 902 Ham bands. After many trials and errors, the new repeater
was born. 900Mhz brought alot of new factors into repeater building for us. Primarily
at 900Mhz small errors show up in big form. Also, the decision was made to follow
the comercial use at these frequencies and use Narrowband Modulation of 2.5Khz.
On top of that many of the ways that we have tested equipment in the past were
no longer available. I had to purchase an RF meter that would work at 900Mhz, my
choice was a Bird Model 43 along with elements in several different power ranges.
The repeater is currently operating from atop an apartment building
in the Western part of Grand Rapids and shares facilities with the
145.410 Repeater. An approximated
coverage map indicates excellent coverage. This map was made with
a program called Radio Mobile. The program was given information about
the height of the antenna, transmit power, reciever sensitivity, feedline
and system losses, antenna type and gain as well as transmit and recieve
frequencies. It uses terrain data and plots a coverage map. The map was
produced for 10 Watts of power output from the repeater transmitter. The
current configuration with the Glenayre amplifier feeds 325 watts to the
50' of 1/2 hardline that goes to the antenna.
At this point I would like to take a few keystrokes to thank all the people
who have helped with make this repeater a reality. Sam Nabkey K8SN provided
the cabinet and Hall Voter, Jeff Emery KI8BW who supplied the RackTrac custom
enclosure to hold the main reciever and transmitter, tower climbers Doug Lemmen
K8BBC and David Buffington KC8HVT, Mike Wolthuis KB8ZGL who found a boatload of
900Mhz MaxTracs, John Ruiz N8JPR, Bruce Sommer N8ODV, Jeff Nawrot N8JSN and all
of the others who helped with carrying and moving equipment and were just there
when they were needed to hand tools and parts to the rest of us. Also thanks to
all of the people on the
AR902Mhz yahoo list who
helped with finding parts for the modifications and provided some technical info
for getting started with the radios, especially Doug Bade who took time out to
get me started on the right foot.
Current plans for the repeater are the addition of several remote
recieve locations for top quality coverage. Design standards for the
remote reciever and links are still in the works. Once again there will
be a bit more learning curve as we are working with some things that
we have not worked with in the past. Also in the plans is a change to
a new RC-110 repeater controller by AH6LE. This controller has some great
possibilities that I will be working on. This is going to be a great up
and coming controller.
Currently we are working with several different radio models for use with the
repeater. All of the radios that we use were made by Motorola and use 2.5Khz
Narrowband FM Modulation. Top choices at this time are the Motorola GTX 900 series
radios both mobiles and portables. These radios work sufficiently well with no
hardware modification. Also in use are some Motorola MTX 9000 portable radios
that also require no hardware modification for operation with the repeater.
Next in line are the Motorola MaxTrac 900 and Spectra 900 radios. The Maxtracs
require hardware modification that is not for the timid or uninitiated. I won't
kid you the modifications require a steady hand and are time consuming. The Spectra
radios also require some hardware modifications. At this time we have not made
the modifications needed for this radio, but it looks like they will be similar
to the Maxtracs.
All of the radios above are programable via software using a Radio Interface Box.
The standard software will not work and I am not aware of any radio dealers that
will program a radio into the ham bands for you. So, before you decide that you
would like to join the people using 900Mhz you will need several items including
a radio, a computer that will run in pure DOS (not a DOS window), a Radio Interface
Box, and Software for programming the radio (Modified using a hex editor). These
are just the minimums. You may also need to do hardware modifications that require
removal and replacement of surface mount components about the size of the head of
a straight pin.
|
