Motorola VRS750, Service Manual

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2
Ordering
Information
The VRS is a crossband repeater that operates on either UHF or VHF
frequencies. The repeater cannot be operated with a mobile radio
operating in the same band as the VRS unit.
The VRS RF platform is based on a synthesized transceiver. The VRS
supports one channel whose frequency and channel spacing can be
programmed in the field. The VRS remains a simplex repeater and as a
result, the transmit frequency must be set equal to the receive
frequency. The VRS receives its programming information from the
ASTRO Spectra mobile at power-up. The ASTRO Spectra mobile
supports the VRS programming fields via ASTRO Customer
Programming Software (CPS). For more information, refer to “VRS750
Programming,” in Chapter 2, “Installation.”
The VRS is not compatible with ASTRO Spectra mobiles with the
VSELP signaling type.
When integrating a VRS with an ASTRO mobile with a Siren/PA, an
alternate interface cable is needed (HKN6154A). This cable allows the
VRS to be connected to the Siren/PA. For more information, refer to
“Installation,” Chapter 2.
When integrating a VRS with an ASTRO mobile with Dual Control
heads, an alternate interface cable is needed (NKN6460A). This y-cable
allows the VRS to be connected to the ASTRO mobile with two control
heads.
A separate antenna (not included) is necessary for use with the
repeater. Typically, a one-quarter (1/4) wave length antenna
maximizes radiation efficiency when installed at the center of the
vehicle roof. If it is necessary to mount the antenna on the vehicle’s
trunk lid, an appropriate 3 dB gain antenna should be used. See “VRS
Antenna Installation,” in Chapter 2, for details.
A filter for the battery lines (TLN5277B) is available for use with ASTRO
Spectra mobiles. This filter can be used to prevent excessive alternator
whine noise from being heard on the mobile speaker during VRS
operation.
The VRS ships from the factory with the low output power setting at
275 mW and a high output power setting of 2 W. The low output
power setting is the default setting. We recommend the LOW Transmit
Power setting of 275 mW for optimal performance. This output power
provides the VRS with a similar range as the portable when attached
to a mobile antenna. Any deviation from this setting could result in a
loss of communication from the portable to the base.
The Global Tuning Tool (not included) can be used to tune the VRS
output power in the field. For more information refer to “VRS750
Global Tuner,” in Chapter 2.
Contact Customer Resources for information on how to obtain this
Global Tuning Tool.