CDR-3250/80 TECHNICAL MANUAL
5-2
Issue 2.2
CAUTION
CAUTION
When working on the receiver with
covers removed and power applied, do
not allow tools or metal objects to come
in contact with receiver components.
Equipment damage may occur.
Unit contains parts and assemblies
sensitive to damage by electrostatic
discharge (ESD). Use ESD precautionary
procedures when touching removing or
inserting parts.
5-4.1
Receiver Sensitivity.
This procedure is used to
check that the receiver's sensitivity is at least 10 dB above
the noise threshold. This procedure may also be used for
troubleshooting by passing a signal through the receiver
and verifying the proper output. If incorrect results are
obtained, perform corrective maintenance in Section II of
this Chapter.
1.
Connect RF signal generator to the ANTENNA
jack J5.
2.
Set the RF signal generator output for a CW
signal of 12.126 MHz at -113 dBm.
3.
Connect true RMS voltmeter to the 600 ohm
NORM audio output, J8 pins 1 and 2 on the
rear panel.
4.
Ensure equipment has warmed up at least 10
minutes.
5.
Set the receiver frequency to 12.125 MHz in
ISB reception mode.
6.
Set receiver manual gain to -000.
7.
Record voltmeter reading to establish refer-
ence.
8.
Remove signal generator input to receiver.
9.
Voltmeter should read at least 10 dB less than
the reading obtained in step 7.
10.
Connect voltmeter to the 600 ohm ALTN audio
output, J8 pins 4 and 5 on the rear panel.
11.
Set the receiver frequency to 12.127 MHz.
12.
Record voltmeter reading to establish refer-
ence.
13.
Remove signal generator input to receiver.
14.
Voltmeter should read at least 10 dB less than
the reading obtained in step 12.
15.
Disconnect test equipment, and reconnect
antenna.
16.
Return receiver to normal configuration.
5-4.2
Line Audio.
The following steps provide
verification and adjustment procedures for the 600 ohm line
audio outputs on the rear panel. If incorrect results are
obtained, perform corrective maintenance in Section II of
this Chapter. To verify/adjust the line audio outputs, do
the following steps.
1.
Connect RF signal generator to the ANTENNA
jack J5.
2.
Set the RF signal generator output for a CW
signal of 12.126 MHz at -70 dBm.
3.
Connect true RMS voltmeter to the 600 ohm
NORM audio output, J8 pins 1 and 2 on the
rear panel.
4.
Ensure equipment has warmed up at least 10
minutes.
5.
Set the receiver frequency to 12.125 MHz in
ISB reception mode.
6.
Set receiver AGC ON.
7.
Voltmeter should read 0 dBm ± 3 dB. If not,
remove top cover of receiver and adjust
NORM AUDIO LINE ADJ potentiometer until
correct reading is obtained. (See figure FO-5A
(CDR-3250) or FO-5B (CDR-3280) ).
8.
Connect voltmeter to the 600 ohm ALTN audio
output, J8 pins 4 and 5 on the rear panel.
9.
Set the receiver frequency to 12.127 MHz.
10.
Voltmeter should read 0 dBm ± 3 dB. If not,
remove top cover of receiver and adjust ALT
AUDIO LINE ADJ potentiometer until correct
reading is obtained. (See figure FO-5A (CDR-
3250) or FO-5B (CDR-3280) ).
11.
Replace top cover if removed.
12.
Disconnect test equipment, and reconnect
antenna.
13.
Return receiver to normal configuration.
5-4.3
Reference Frequency.
The following steps
provide verification and adjustment procedures for the
internal reference frequency.
NOTE
In the following procedure, a
strong, off-the-air, accurate,
f r e q u e n c y s t a n d a r d u s i n g
amplitude modulation (such as
WWV) may be used as the
frequency standard. Use highest
frequency possible below 30.0
MHz.
Courtesy of http://BlackRadios.terryo.org
