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This is the Motorola outdoor
cabinet that the receive site is mounted in. This photo was taken
when it was located in the
office at the Range Township Firehouse in Sedalia (Midway) Ohio.
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Here are two views inside of
the cabinet - front and rear. The GE transmitter is at the top,
the Motorola receiver and controller card in the middle, and the
monster
power supply on the bottom.
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This is a close-up of the GE
Mastr-II transmitter mounted onto a 19" rack panel. Below that it
the Motorola Spectra-TAC chassis that holds the Micor receiver,
audio-squelch board, and controller card.
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This is the new
microprocessor-controlled controller card that is installed in the
Spectra-TAC chassis. It was under development for 6 months. The
goal was high performance, low cost and simplicity. There is only one
adjustment to calibrate. It contains a DTMF decoder, CTCSS decoder, and
a PIC microcontroller to run the whole show. The complete schematic and
layout is here. (PDF -1MB). The
controller has several modes, such as carrier access, CTCSS access
only, carrier access with CTCSS boost, and others. During periods of
interference, it is possible to put the site into CTCSS protect or
disable it completely for 1 hour, then it will automatically return to
its previous mode.
The CTCSS decoder is also a PIC microcontroller, using a specialized
version of a FFT (Fast Fourier Transform) called the Goertzel Algorithm
to detect the CTCSS tone.
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An inside view of the Bud
Box
that contains the GE Mastr-II exciter board, the COR interface board
mounted on the side of the box (seen here at the bottom-center of the
photo) and the modified crystal oscillator (it's in the channel
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This is the antenna
configuration at Mt Sterling. The tower is about 70 feet high,
and our
antennas are side mounted at about 55 feet. The 2 meter receive
antenna is a Hustler G6-144B, and the UHF link antenna is a PC-Tel
BMOY-4450.
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The Tri-County Firehouse
#491 in Mt. Sterling, OH, located on SR-56 at US-62 in the center of
town. The tower is directly behind the firehouse, as seen here in the
middle of the photo.
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