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0
CABLE
0
ANT
CONNECTOR
O
4705 —101<Q
MA,
TO MEASUREMENT
POINT
BELOW HUNDREDS
OF PF
O
PICK-UP COIL
(VINYL-COVERED
WIRE, 10— 30
TURNS)
PICK-UP FROM
TANK COIL, ETC.
EXAMPLES OF ATTENUATOR
TO MEASUREMENT
POINT
CABLE
capacitance and others of the cable from affect-
ing the circuit under measurement. A series
resistor is effective in measuring high-impedance
circuits and a series capacitor is adequate for high
frequency circuits. The higher the signal level
of the circuit under measurement, the higher the
resistor or the smaller the capacitor can be
placed. Therefore, it is recommended that the
resistor be as high and the capacitor as small as
the DG-5 can measure. This is useful to minimize
affecting of the DG-5 to the circuit under
measurement.
As your DG-5 has a very high sensitivity, it
could pick up the transmit wave or the waves
leaking from connection cables, particularly
in measuring low frequencies. This could result
in irregular frequency counting. To prevent such
an adverse effect, also, the series resistor or
attenuator is adequate.
The COUNT. IN connector withstand
voltage is 200V DC at the peak value or 5V AC
at the root-mean-square value. For measuring
the frequencies at most electron tube circuits
and at the outputs of transmitter final stages, be
careful not to directly connect the counter cable
to any of the high voltage points and antenna
connector.
Should an input exceeding the withstand
voltage come into the connector, the counter
input resistor could be burnt out. To prevent
such an accident, place a capacitor as small
as 1 to 2pF in series or use a pick-up coil by
winding around the antenna coaxial cable or
bringing near the circuit which is, for example,
a tank coil as illustrated in Figure 5.
ANTENNA COAXIAL
CABLE
TO MEASUREMENT
POINT
•
1
0
CABLE
OVER SEVERAL TENS OF
kD (MAY BE PLACED)
Figure 5. Counter Cable Coupling Methods for High-Tension,
Low Impedance, High Frequency Circuits.
8
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