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o
70 DB.
If AM noise is high,
it can actually originate in most
any stage.
However,
if, upon analyzing the type of noise,
it
is found to have
a
basic 120 cycle component the power supply
should be suspected.
If the noise appears to be mostly a 60
cycle component a heater to cathode leak in any stage should
be suspected.
A loose connection in any stage will
-
cause the
AM noise to rise when the exciter cabinet is jarred.
A point
often overlooked when making AM noise measurements
is
the samp-
ling loop or device.
For eximple;
if the RF sampling loop is
mounted in a PA chamber where blower vibration is apt to occur,
this vibration will show up as high AM noise,
if the sampling
loop is not securely mounted.
TYPICAL PROOF OF PERFORMANCE READINGS
If the exciter unit has been shipped as an individual unit the
complete test data sheet will probably have been filled out and
included in this section.
If the exciter unit is part of a high
power transmitter the test data sheet is included with the
overall instruction book.
A set of typical readings for
proof of performance is given
below:
Carrier Frequency,
O.K.
o
Distortion at
100% modulation
Response with reference
to standard
75
micro-
second pre- emphasis curve
30
cycles
1.75
- 1.7
DB
50 cycles
. 85
-
. 2
100 cycles
. 56
7'
. 5
400
cycles
. 47
7
/ . 8
1000 cycles
. 42
7
1
. 8
2500 cycles
. 38
/
. 5
5000 cycles
. 34
7 1
. 4
7500 cycles
. 58
7
1
. 3
10,000 cycles
. 58
7
1
. 1
-
18-
M6095 Exciter
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