Lectrosonics VRFIELD (Narrowband) - Manual (Page 25)

Digital Hybrid Wireless™ Modular Receiver System
Antenna Use and Placement
The VR Field System is designed for rack mounting.
Although it can be operated with two whip antennas, it
is best to use remote antennas such as the SNA600
or ALP700 for optimum reception. Position the remote
antennas at least three or four feet apart and not within
three or four feet of large metal surfaces. If this is not
possible, try to position the antennas so that they are as
far away from the metal surface as is practical. It is also
good to position them so that there is a direct “line of
sight” between the transmitter and the receiver anten­
nas.
In situations where the operating range is less than
about 100 feet, the antenna positioning is much less
critical. However, the length of the cabling between
antennas and the system is critical. Long cable runs
can experience serious signal loss. Lectrosonics offers
in-line RF amplifiers suitable for compensating for this
signal loss. Contact your dealer or the factory for more
information.
A wireless transmitter sends a radio signal out in all di­
rections. This signal will often bounce off nearby walls,
ceilings, etc. and a strong reflection can arrive at the
receiver’s antennas along with the direct signal. If the
Phantom Power
direct and reflected signals are out of phase with each
other and similar in strength, a cancellation (“dropout”)
may occur. A dropout can sound like audible noise
(hiss or swishing), or in severe cases, it may result
in a complete loss of both the carrier and the sound.
Moving the transmitter even a few inches will change
the sound of the dropout, or may even eliminate it. A
dropout situation also may be either better or worse as
a crowd fills or leaves the room.
The VR Field System offers a several sophisticated
diversity designs which can overcome most dropout
problems. In the event, however, that you do encounter
a dropout problem, first try moving the one of the re­
mote antennas at least three or four feet from its current
location. This may alleviate the dropout problem at that
location. If dropouts are still a problem, try moving the
antennas to entirely different locations.
Lectrosonics transmitters radiate power very efficiently,
and the receivers are very sensitive. This reduces
dropouts to an insignificant level. If, however, you do
encounter dropouts frequently, call the factory or con­
sult your dealer. There is probably a simple solution.
Warning: Phantom power operates independently of the power switch.
When using battery power, you must disconnect the battery when the
Remote antennas can be
placed at a distance from
the VRF to optimize recep­
tion. To overcome loss in long
coaxial cable runs, a Lectro­
sonics UFM Series inline RF
filter/amp can be positioned
at the far end of the coaxial
cable, close to the antenna,
or use ALP650 antennas with
built-in RF filter/amps. With
amplifier in this position, gain is applied ahead of the
loss to maximize the signal to noise ratio of the antenna
system.
Power for the UFM of ALP650 can be supplied by the
VRF assembly through the coaxial cable by setting
jumpers on the main PC board toward the center of the
board as shown. Disconnect power from the VRF, then
remove the top cover for access to the jumpers.
Location.of.Jumpers
Jumper positioned to
enable DC power
VR Field is not in use to prevent the battery from continuously discharging.
CAUTION: It is best practice to enable this DC power ONLY
when a remote amplifier is used. Some antennas may
present a short to the power supply. While the power supply
is fused and it is unlikely that damage would occur to the
VRF, it is always best to disable the DC when it is not in use.
Rio Rancho, NM