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Model 451E
Section III
Paragraphs 3-1 to 3-14
SECTION I!!
OPERATING INSTRUCTIONS
3-1. INTRODUCTION,
3-2. This section contains information and procedures
for operation of the Model 415E (from either AC or bat¬
tery power source) in making swr and attenuation
measurements. Also included is information on slotted
line techniques, instruction in the use of a Smith Chart
for plotting load impedance, and discussion of Model
415E noise performance with various source imped¬
ances and noise effect on meter indication.
3-3. FRONT AND REAR PANEL FIXTURES.
3-4. Figures 3-1 and 3-2 identify by number the front
and rear panel fixtures of the Model 415E.
The des¬
criptions in Table 3-1 are keyed by number (1-12 for
front, 13-18 for rear) to the figures.
Further infor¬
mation regarding the various settings and uses of the
controls, indicators, connections, and adjustments is
included in the procedures of this section. Information
on battery is found in Paragraph 3-6.
3-5. GENERAL OPERATING AND
MEASUREMENT CONSIDERATIONS.
3-6. BATTERY OPERATION.
3-7. The Model 415E may be operated from a battery
instead of the 115 or 230 volt AC supply (see Paragraph
2- 13).
Battery operation requires some slightly dif¬
ferent procedures to prolong battery life and to ensure
proper results.
The rechargeable nickel - cadmium
battery is factory installed if ordered as Option 01 (see
Paragraph 1-7).
The same battery may be ordered
and installed later.
To obtain this, order hp Stock
Number 00415-606, Rechargeable Battery Installation
Kit.
3- 8. INITIAL BATTERY USE.
When the Model 415E
is to be battery operated for the first time, perform
the following steps:
a. Switch the Model 415E POWER switch to BAT-
TERY/TEST position and note meter pointer indication:
A meter pointer indication in the "BAT. CHARGED"
area indicates the internally battery properly charged
and ready for use: A meter pointer indication to the
left of the "BAT. CHARGED" area means that the
battery must be charged as described below.
b. Connect the Model 415E to AC power source. Set
POWER switch to BATTERY/CHARGE and charge the
battery for a minimum of 16 hours or overnight.
c. After at least 16 hours of recharge time, switch
POWER switch to BATTERY/TEST position and check
battery charge. If the battery charge indication is still
unsatisfactory, see Paragraph 5-35.
3-9. OPTIMUM BATTERY USAGE. It is recommended
that the Model 415E be operated by the battery for up
to 8 hours, followed by 16 hours of recharge.
If con¬
tinuous battery operation is required for more than 8
hours, the recharge time should be double the oper¬
ating time.
Continuous battery operation is possible
for up to 36 hours but this must be followed by a pro¬
longed recharge period.
3-10. BATTERY STORAGE. Storage of the battery at
or below room temperature is best. Extended storage
at high temperatures will reduce the cell charge but
not damage the battery if the storage temperature is
less than 140°F.
It is suggested that the battery be
charged after removal from storage and before using
the Model 415E for battery operation.
3-11. GROUNDLOOP CURRENTS.
3-12. The 415E SWR Meter audio amplifier has high
sensitivity to low level signals. To reduce ground loop
currents, the 415E grounds are isolated by a 46.4 ohm
resistor.
Ground loops occur when instruments are
connected to415E outputs and grounded through power
cords or rack mountings.
Ground loops can be min¬
imized in the following ways:
a. Connect the 415E to instruments with floating-
inputs;
b. Connect the 415E to instruments with high input
impedance;
Connect only the signal wire between in¬
strument and the 415E;
c. Operation at higher signal levels;
d. An Adapter on the power cord to float the instru¬
ment ground where not prohibited by safety regulations.
3-13. BANDWIDTH AND FREQUENCY SELECTION.
3-14. Two front panel adjustments are provided to op¬
timize operation of the Model 415E tuned amplifier.
The FREQ (frequency) control allows a total variation
of 7% of the center tuned frequency.
When more than
one Model 415E is included in the same measurement
setup, the variable tuned frequency is used to set all
the instruments to the exact frequency modulating the
source.
The high sensitivity and narrow bandwidth
of the amplifier make the Model 415E valuable as a
meter-indicating null detector for audio frequency
bridges. The BANDWIDTH adjustment varies the tuned
filter bandwidth from 15 to 130 cps.
A narrow band¬
width is best for low level signals as this improves
the signal to noise ratio. A wide bandwidth would find
more use in fast sweep rate measurements.
02152-4
3-1
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