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|The entire repeater (except
for the 4-can duplexer) is installed a half-height Motorola equipment
cabinet. The Astron RS-35 Power Supply is located on the
bottom. Above that is the rack containing the 4 receivers and the
voter (see photos below.) Above that is the Hamtronics REP-200
Repeater Controller. The large unit at the top is the 100W VoComm
|This is the rack containing
the 4 receivers and the voter. The rack is a Vector CMA13-20/90
Subrack and the individual modules are type EFP. Two receiver
modules are on each side, and the voter module is in the middle.
(When this photo was taken, only 3 receivers were installed, hence the blank panel near the center.)
|This is the rear view of the
receiver and voter rack.
|A receiver module. Each
receiver is installed in a separate module for improved shielding and
isolation. The large knob on the bottom is the volume control for
a local speaker, and the smaller upper knob is the squelch
control. These receivers are very sensitive and selective - all
measured less than 0.12uV sensitivity for 12 dB SINAD.
|The rear view of a receiver
module. All of the connections are made at the rear panel.
The RCA jacks at the top connect the audio and COR signals to the
voter. 12VDC is connected to the middle power jack. The
antenna connects to the SO-239 jack at the bottom.
|An inside view showing the
Hamtronics R-30x receiver mounted in the Vector EFP module. The volume
and squelch controls had to be remounted on the circuit board in order
to fit in the module. All connections on the rear panel are
bypassed with capacitors and filtered with ferrite beads. (Except for
the antenna lead, of course!)
|The DHE 4-RV Voter Card was
also mounted in a EFP module. Added to the front panel are 4
select switches to manually disable any of the receivers. At the lower
right are 4 green LEDs to show which receiver is currently voted, and 4
red LEDs to indicate which receivers are receiving a signal.
|An inside view of the voter
module. The perf-board circuit on the left is the microcomputer
the generates the CW reset beep indicating which receiver was voted the
most. The microcomputer is a PIC16F628. The assembled
program is 730 words long and uses 48 bytes of memory.
|This is the 140 ft tower at
the Madison County Hospital. Our repeater antenna is side-mounted
at the 100 foot level. It is a Decibel Products DB-224 4-dipole array
with 3 to 9 dB of gain. Since it is side-mounted on the tower,
the gain will vary depending on the direction - approx 9 dB gain
towards the North and East , and about 3 dB to the Southwest.
The three UHF link antennas are about 15 feet below the repeater antenna. Each one points to its respective remote receiver in Sedalia, Plain City, and West Jefferson.
|A close-up view of the three
UHF link antennas. They are Cushcraft A449-6s yagi beams with
about 10 dB of gain.
|Copyright © 2006 All rights reserved Donald Kovalchik||
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|This page last updated January 30, 2006||