West Mountain Radio
The 12V voltage comparator & audible alert
A feature of the RIGrunner 4012 and 4008 is the precision
expanded scale voltage comparator display with audible
alert. (The 4004U, 4005, 4006U, 4005H and 4008H models
do not have this feature.) A basic explanation of 12 volt
systems will aid in understanding this feature. Equipment
commonly referred to as 12 volt is actually a nominal 13.8
volts. For example, a lead acid battery is a nominal 12.6
volts when charged and not under load, and approximately
14.0 volts under charge. A quality 12 volt power supply will
have its regulated output set to 13.8 volts. Most radios are
specified to require 13.8 volts +/- 15%. 12 volt automobile
or aircraft alternators have voltage regulation set between
13.5 and 14.3 volts.
The RIGrunner provides an accurate and unambiguous
display of voltage. There are three LEDs: red overvoltage,
green normal, and yellow undervoltage. The points at which
the LEDs change are set accurately to 11.5 and 15.0 volts.
The selection of these points gives a reliable indication of
proper and safe operation of your power supply, battery or
alternator. A green or normal indication is all you need to
look for.
An undervoltage indication, shown by the yellow LED, is
less than 11.5 volts. This should be safe for your radio, but
may cause improper operation. Low voltage on a modern
radio can cause a loss of phase lock and a frequency error.
This is a definite indication of a problem with the power
source; a bad connection, an unregulated power supply, a
bad alternator or dying battery. It is normal with most cars to
have less than 11.5 volts when cranking the starter motor.
A normal indication with the green LED illustrates, everything
is good and you are between 11.5 and 15.0 volts, do not
worry about a thing.
A red overvoltage indication with the red LED is a warning,
DISCONNECT OR TURN OFF YOUR POWER SUPPLY
IMMEDIATELY! It is possible to overheat or damage a radio
or other equipment. An overvoltage will sound an audible
alert; no need to watch the LEDs to signal a problem.
When running strictly on a 12 volt battery, an overvoltage
condition will not occur. The RIGrunner’s audible alert can
be reconfigured for a low battery warning. By removing the
four cover screws and move the P14 jumper to the “LO”
position. Remember to move it back to “HI” when changing
back operation from power supply or alternator.
Note:
Due to the characteristics of the comparator chip
it is normal for the undervoltage LED to glow very dimly
with a normal or overvoltage indication. It is also normal
for the LEDs to change intensity while stepping through 10
precision points.
In the event of a bad power source or power connection,
the yellow LED may flash or come on during transmit. If
this happens, check the power source and connections.
It is also possible for RF from a transmitter to cause an
electronically regulated power supply to lose regulation and
cause an overvoltage alert during transmit. The RIGrunner
