Icom IC-756ProIII Installation Notes
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Also See for IC-756ProIII:
- Instruction manual (124 pages) ,
- Service manual (119 pages) ,
- Installing manual (4 pages)
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Icom IC-756ProIII Installation Notes (Draft)
1. Overview
Most modern Amateur transceivers now generate their operating frequency from a single
internal Reference Oscillator. In many cases, this Reference Oscillator is voltage-controlled,
allowing front panel adjustment of the Reference frequency.
The XRef-PLL locks the radio's Reference Oscillator to an external 10 MHz reference signal
from a GPS reference or other high-accuracy source. It intended to be installed internally within
the radio. When no 10 MHz reference is connected, the XRef-PLL completely disconnects from
the radio, allowing it to operate as from the factory.
In the case of the Icom IC-756ProIII, the Reference frequency is 32.0 MHz.
A Word of Caution: The installation requires a small amount of soldering to very small and
fragile SMD components. If you do not have experience with SMD techniques, please seek
the assistance of someone who does. We are happy to provide any advice needed, but we
cannot take responsibility for any damage to your radio.
2. Technical Specifications
Connections to the board are shown below:
Test
Lock
Vp
Gnd
Vin
Connection
Test
Lock
Vp
Gnd
Vin
Ref
RF
Ctl
XRef-PLL
Description
Do Not Connect
PLL Lock Indicator
Do Not Connect
Power Ground
Supply for XRef
10 MHz Reference Input
Reference frequency from Radio.
Control output to Reference VCXO
Ref
Gnd
RF
Gnd
Ctl
Specifications
+3.3V 20mA max
5 to 16 V @ 20 mA
0 to +15 dBm
(0.5V to 3.6V p-p)
Radio dependent
0 to +3.3V
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Summary of Contents for Icom IC-756ProIII
- Page 1 When no 10 MHz reference is connected, the XRef-PLL completely disconnects from the radio, allowing it to operate as from the factory. In the case of the Icom IC-756ProIII, the Reference frequency is 32.0 MHz. A Word of Caution: The installation requires a small amount of soldering to very small and fragile SMD components.
- Page 2 PLL board. An extract from the circuit diagram in Figure 1 shows where connections are to be made. Figure 1. – Icom IC-756ProIII Reference Oscillator Circuit The Blue arrow indicates where the output of the Reference Oscillator is sampled.
- Page 3 Figure 2. – PLL Board Location The connection points are shown in Figure 3. The green connections are on the left edge of the PLL board. Figure 3. – PLL Board Reference Oscillator Connections...
- Page 4 There are two possible points (two green arrows) for controlling the Reference Oscillator. The point with the dark green arrow should be more sensitive. Connect the NPN transistor with Collector to whichever of these points you choose, and Emitter to ground. Using thick double-sided foam adhesive tape, mount the XRef board either on top of a shielded box or in some other suitable location near the Reference Oscillator.
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