Country Home Products Wireless Microphone Systems - Manual (Page 42)

SYSTEM SETUP: BATTERIES
Always use fresh batteries of the correct type in the
transmitter and/or receiver. Most manufacturers
recommend only alkaline type batteries for proper
operation. Alkaline batteries have a much higher power
capacity, more favorable discharge rate and longer storage
life than other types of single-use batteries such as carbon-
zinc. Alkaline types will operate up to 10 times longer than
so-called "heavy duty" non-alkaline cells. They are also far
less likely to cause corrosion problems if left in the unit.
Consider bulk purchase of alkaline batteries to get the greatest
economy: they have a shelf life of at least one year. The
battery condition should be determined before system use
and checked periodically during use, if possible. Most
transmitters are equipped with a battery status indicator of
some kind that will at least indicate a go/no-go or some
minimum operating time. Some units have a "fuel gauge" that
can allow more precise indication of remaining battery life. A
few models even have the capability of transmitting battery
condition information to the receiver for remote monitoring.
Use rechargeable batteries with extreme caution: their
power capacity is much lower than the same size alkaline
and their actual initial voltage is usually less. The
conventional rechargeable battery uses a Ni-Cad (nickel-
cadmium) cell or Ni-Mh (nickel-metal-hydride) cell. The
voltage of an individual Ni-Cad or Ni-Mh cell is 1.2 volts
rather than the 1.5 volts of an alkaline cell. This is a 20%
lower starting voltage per cell. The standard alkaline 9-volt
battery is made up of six cells in series, which yields an
initial voltage of at least 9 volts.
The typical "9-volt size" rechargeable also has six cells,
giving it an initial voltage of only 7.2 volts. When combined
with its lower power capacity the operating time may be
less than 1/20 of an alkaline, only about 15 minutes in
some units. The "better" 9-volt size rechargeable has
seven cells (8.4 volts initial), but still has only about 1/10
the operating time of an alkaline. It is possible to obtain
9-volt size Ni-Cad batteries that have eight cells (9.6 volts
initial) but even these have less than half the alkaline
operating time and are expensive. (See Figure 4-7.)
If it is decided to use rechargeable batteries, battery
management is very important. For systems in daily
service a minimum of three batteries per unit is
recommended due to the charging time: one charged, one
charging, and one in use. In addition, Ni-Cad batteries must
periodically be completely cycled to get maximum service
life and avoid developing a short discharge "memory."
Ultimately, the long-term potential savings in battery cost
must be weighed against the short operating time, initial
investment and ongoing maintenance requirements for
rechargeable batteries. Experienced users almost
invariably choose alkaline batteries.
SYSTEM CHECKOUT
AND OPERATION
Good practice with any wireless microphone system
calls for a checkout of the system ahead of performance
time. As suggested in the squelch adjustment section this
should be done with all associated production equipment
also on. This may reveal potential problems that are not
apparent in a wireless-system-only test.
Pre-Show Checkout:
1) Verify good batteries in all transmitters.
2) Turn on all receivers (without transmitters)
and all antenna distribution equipment. All
receivers should show little or no RF activity.
3) Turn on individual transmitters one at a time to
verify activation of proper receiver. Transmitters
should all be at a comparable distance (at least
5 meters) from receiving antennas. Off-channel
receivers should show little or no RF activity.
4) Turn on all transmitters (with receivers) to verify
activation of all receivers. Transmitters should
all be at a comparable distance (at least 5
meters) from receiving antennas and at least
1 meter from each other.
5) Perform a stationary listening test with each
individual system one at a time to verify proper
audio level settings.
6) Perform a listening test around the performance
area with each individual system one at a time
to verify no dropouts.
7) Perform a listening test around the performance
area with each individual system while all
systems are on to verify no audible interference
or dropouts.
43
Selection
and Operation
of W
ireless Microphone Systems
C
H A P T E R
4
Figure 4-7: alkaline vs. rechargeable batteries