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62
·roo
~oo
~~
0
0
0
0
,·.roo
·roo
~f~
0
0
0
0
0
........
Frequency
(Hz)
0
0
0 0
3C.
o o
ioo
o o
·roo
o o
·roo
o
o
'4oo
o o
' 5 00
0
0
600
0
0
0
700
0
0
00000900
0 0
1000
0
0
0
0
IMI&r,...
Frequency
(Hz)
........
l===lbl
QP 1102
D
0
D 0
jo
0
lO<'
0
o
'roo
0
0
·roo
o
o
'too
o
o
roo
ooroooo
roo
o
orloooo
·~ oo1~0
0
0
0
0
.....
.,..
Frequency
(Hz)
........
l===!c)
I
""'
~
...
.
...,.._
-
-
QP 1102
Fig. 5.
7.
Analysis examples of a deterministic signal with (a) Direc-
tion Analysis (b) High Speed Analysis using 7502 alone (c)
High Speed Analysis using 7502 with 5623
Such frequency transformation can be made by means of a continuous tape loop on a
high quality tape recorder, such as the 8 & K Types 7003 or 7004, but a more versatile
solution uses the Digital Event Recorder 7502. Full details of the use of the 7502 for
frequency transformation and analysis are given in the 8 & K Technical Review No. 2,
1973. It is recommended that the frequency range of
interest
is analysed
in
blocks of
one decade in order to achieve the greatest transformation ratio and therefore the fas-
test analysis. It is also advantagenous to use a supplementary time window function on
the transformed signal. This suppresses the sudden transition at the signal junction of
the continuously looped signal, the effect of which would otherwise appreciably affect
the selectivity of the analysis
.
This effect is shown in Fig.5. 7 (a) and (b). Addition of a
Gauss Impulse Multipler 5623 (Fig.5. 7(c)) suppresses the side bands associated with
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