OptOnal Ut-108 NstallatOn; OptOnal Ut-109/Ut-110 NstallatOn - Icom IC-F521 Instruction Manual
Vhf/uhf transceiver
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Also See for IC-F521:
- Instruction manual (24 pages) ,
- Service manual (38 pages) ,
- Instruction manual (8 pages)
Table of Contents
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3
CONNECTION AND MAINTENANCE
■ Optional UT-108 installation
Install the optonal UT-108 unt as follows:
q Turn power OFF, then dsconnect the DC power cable.
w Unscrew the 4 screws, then remove the bottom cover.
e Install the unt as shown n the dagram below.
r Replace the bottom cover and screws, then the DC
power cable.
15
UT-108
■ Optional UT-109/UT-110
installation
q Turn power OFF, then dsconnect the DC power cable.
w Unscrew the 4 screws, then remove the bottom cover.
e Cut the prnt pattern on the PCB at the TX mc crcut (A)
and RX AF crcut (B) as shown n the followng figure.
r Install the scrambler unt as shown n the left.
t Return the bottom cover and screws to the orgnal pos-
ton.
A
NOTE: Be sure to re-solder above
dsconnected ponts, otherwse no TX
modulaton or AF output s avalable
when you remove the scrambler unts.
Front panel
B
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Questions and answers
How to control squech
The squelch on the Icom IC-F521 is controlled by a noise squelch circuit. This circuit detects noise components in the AF signals and switches the AF mute switch accordingly. The squelch level is managed by a level controller (IC6, pins 21, 22), which processes signals from the FM IF IC (IC1, pin 9) and applies them to an active filter section (IC1, pin 8). Noise components around 10 kHz are amplified and converted into pulse-type signals by the noise detector section.
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