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Model 606A
Sect. II Page 7
EXTERNAL
MODULATION
FREQUENCY
MODULATION
AMPLITUDE
VERNIER
MODULATION
SELECTOR
ATTENUATOR
1.
oon
Ex.
Cw
IW
o
—_"—_—
ie
os
°
7,
SY)
tl
D
0
| eum oe
it?
—"20
03
CRYSTAL CALIBRATOR
RE OUT
PHONES
OFF
50.0,
1. Perform
procedure
for CW
operation (see
Figure 2-2).
2. Set MODULATION
SELECTOR
to EXT (AC
or DC coupling).
3. Connect modulating signal (3 volts or more
adjustable) to MOD, terminal.
4,
Turn
MODULATION
AMPLITUDE
fully
clockwise.
5. Increase signal from external generator until
a reading of 100% is obtained on the PERCENT
MODULATION Meter.
6. Reduce
the percent
modulation
to the de-
sired level with the MODULATION
AMPLI-
TUDE control.
The limits of modulation depend upon the maxi-
mum
tolerable
envelope
distortion. For three
percent envelope distortion the limits in terms
of the carrier frequency, f,, are:
Square—
30% Mod.
_70%Mod.
Wave Mad.
ae
ax:
= . 06 fi
.02 te
.003 f
absolute
fmod. max.
=
20 kc
20 kc
3 ke
Applying these formulas, typical bandwidths are:
Carrier Freq.
Modulation Frequency
Frequency
30% Mod.
70%Mod.
Square Wive
50 kc
3 kc
lke
150 cps
200 ke
12kc
4 ke
600 cps
500 ke
§=20 kc
10 kc
1500 cps
Imc &above 20 kc
20 kc
3 ke
NOTE
- On the 3 VOLT
output range and le-
tween
19 - 65 mc in frequency, modulation te-
yond 30% is not recommended,
Figure 2-5
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