Precautions; Battery And Oscillation Coil Loading; Obtaining A Dip Point; Measuring Transistor Resonant Circuits - Kenwood DM-81 Manual

KENWOOD DM-81

PRECAUTIONS

Battery and Oscillation Coil Loading

Taking the coil compartment out, you will find a battery snap connector inside the unit.
Fit the snap to the battery. First lay the battery take-out ribbon into the battery holder,
then install the battery in place. Place the supplied oscillation coils into the coil
compartment and reinstall into the dip meter main body.
Verify that the battery is serviceable before operating your DM-81. First, turn the
POWER switch on. Set the FUNCTION switch to "BATT CHECK". The battery is
usable as long as the meter pointer is within the "B.C" zone. A low battery results in
weak or unstable oscillation, no oscillation, or frequency error. Replace the battery when
weak.
After use, be sure to turn the POWER switch off. If your DM-81 will not be used for a
long period of time, remove the battery. You can easily remove it by pulling the take-out
ribbon toward you. Never remove the case screws.

Obtaining a Dip Point

The closer the dip meter is brought to the resonant circuit being checked, the tighter the
two are coupled and the deeper the dip point. However, the tuning point becomes so
broad that you cannot find the correct resonant frequency. Therefore, it is advisable to
move the dip meter a little away from the circuit.
Note that the A band has a large pull-in effect and therefore the dip point is broad.

Measuring Transistor Resonant Circuits

There is no load problem in measuring vacuum tube resonant circuits. In measuring some
resonant (tuning) circuits in transistorized transmitters and receivers, the resonant point
cannot always be found by the dipping load. In this event, temporarily disconnect the
transistor or operate the given resonant circuit with power on and measure by absorption.

Caution in Measuring Transmitters

Your DM-81 is usable as an absorption frequency meter in measuring transmitter power
amplifier tank circuits and similar stages producing high RF energy. In rneasurement, do
not abruptly bring the dip meter close to the circuit as the transistors and other parts in the
dip meter could be destroyed by excess RF energy. Bring it near the circuit slowly while
observing the meter pointer.
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