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amplifier. By using preprinted frequency calibrated recording paper the
frequency response of the projector can now be recorded automatically.
It should be noted that the influence of possible
standing
waves may be
minimised by using the internal frequency modulation of the BFO.
Projector
Water
~
I
L __________ J
Fig. 5.12. Set-up to automatically record the frequency response of a projector.
Use is here made of the combined BFO and Level Recorder Type 2305, i.e.
"Automatic
Frequency Response Recorder Type 3306.
-
0 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0 0
0
0
0
0
0
0
0
0
d
BrU~jatr+
Briloi&K~
a.o.I&K~
5025
Meosu"ng Objoct'---dB d
Eiezoelekt[iscber
20
Errew·f
Mode:::~
209
30
15
z..,
L ..
,_Popor
Sp.:_L
20 10
L
lim. F"2.Q{lltoc.
No,
_ _
Po"_5_0_o.,.,
_ _
10 5
Wr. Sp.:_2Qj)_Sign.:
_ _
R~--F-Scolex_:_
0 0
20000
50000
100000
-~!lao
1000
2000
5000
10000
OP 0123
1000
10000
100 000 Hz
161777
Fig.
5.13.
Recording taken with the
set-up
in Fig.
5.12.
Directional Characteristics of Projectors.
The directional
characteristics
of an echo-sounder
(projector)
may be meas-
ured by the combination shown in Fig. 5.14.
A projector and a hydrophone are placed in a free field under water, the
projector being electro-mechanically rotated on the Turntable Type 3921
36
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