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for instance, the regulation voltage
changes at a rate corresponding to
100 Hz/s the signal frequency will
be 1,5
X
1
o-
3
X
100
=
0,15 Hz
"behind". The settling down time of
the VCO is 30 ms. In addition to
these control voltages the output fre-
quency of the VCO can also be con-
trolled by an AFC circuit which can
be switched into operation in con-
nection
with
the
four
narrower
bandwidths of the analyzer. In order
to cover the necessary frequency
range the output signal from the
VCO, which covers the range from
1,2 MHz to 1
,0
MHz (output range
0 to 200kHz) , is fed to two conver-
ters which each decrease the range
by one decade. The first converter
has
a
range
of
1, 2 MHz
to
1,1 8 MHz
(output
range
0
to
20kHz) and the second has a range
of 1 ,2 MHz to 1,198 MHz (output
range of 0 to 2kHz). In this way the
same relative frequency stability is
obtained in all three ranges.
Frequency Counter
A counter circuit measures the
frequency of the signal generated
by the voltage-controlled oscillator
and displays it on the built-in six di-
Examples of Use
Measurements on Hi-Fi Amplifiers
The
Heterodyne
Analyzer
Type
2010
is
an
excellent measuring
tool for performing a wide range of
measurements on high fidelity am-
plifiers
.
Fig. 5 shows an example of
such a set-up where a Level Recor-
der Type 2307 is used to obtain a
graphical
representation
of
the
measurements.
A frequency response measure-
ment can be made with the switch
in
position
"1 ".
In position
"2",
si-
multaneous measurement of hum,
noise, and cross-talk can be carried
out. The recording in Fig.6 is made
with the switch in position
"2".
The
hum content is seen to be dominant
at 50 Hz and 150Hz. Outside these
frequencies the noise content
is
no-
ticed at the lower and middle fre-
quencies while at higher frequen-
cies
the
cross-talk
becomes
the
most prevalent component.
Frequency Response Recording at
Low levels
Fig. 7
shows the frequency re-
8
"Pull-in" range in Hz (Limit: 0,5 dB error in level)
~
3,16 Hz
e
X
0,1
10
X
1
10
X
10
10
"Pull-in" speed in Hz/s
~
3,16 Hz
e
X
0,1
1
X
1
1
X
10
1
git 7-segment display. The counting
time is selected with the three-posi-
tion COUNTING TIME selector in its
two first positions and
is either
0,1 s or 1 s. In the third position
the analyzing frequency of the anal-
yzer section is displayed when this
is externally tuned. The counting
time in this position is 1 s. A spe-
cial output from the counter is avail-
able for control of an event marker
on recorders, and a switch on the
back
panel
gives
the
choice
of
marker pulses in the range 1 Hz to
10kHz
depending
on
frequency
range setting.
Heterodyne Analyzer 2010
Analyzed signal
10Hz
31,6 Hz
100Hz
-
-
-
100
100
-
100
1000
1000
10Hz
31,6 Hz
100Hz
-
-
-
20
20
-
20
200
400
Automatic Frequency Control
(AFC)
The Analyzer is equipped with an
AFC phase detector circuit control-
ling the Voltage Controlled Oscillator
and thereby the tuning of the instru-
ment. The AFC circuit is active in
the four lower bandwidths ( 3,1 6 to
100Hz). This circuit is intended to
be used when measurement is car-
ried out on a signal of varying fre-
quency. In the tables above, the fre-
quency
range
and
the speed of
"Pull-in"
are given as a function of
the
set
bandwidth
and
the
fre-
quency range used.
Level Recorder 2307
ifier
Electrical
or
mechanical
sweep
drive
--1
I
173301/
1
Fig.5. Example of set-up for measurements on Hi-Fi stereo amplifiers
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&
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Speed:_l_lfVn/>ec.
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Measuring Obj.:
v~:: ~~
~::~: ~~~~~0~1(
,limit
N01se ana
Cross-Talk
16·145
of
Am~lifier
1
4
·130
~
II
II
-~~
'
l2·l1s
-~
I==
I==
~
D c . t a : _
Sign.:
JAH
c
I
o.l o
QP1124
10
20
Hz
so
100
200
500
1000
2000
sooo
200()(
40000 0 A B
C
lin.
Multiply Frequency Scole by
:Z..OL.e.el:
A B C
lin.
113308
Fig.6. Simultaneous recording of hum, noise, and cross-talk
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