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4. Construction
4.1 General construction tips
The kit comes as a main board, plug-in Si5351A synthesiser module, and a plug-in low-pass-filter module
for the desired band.
The Si5351A synthesiser module and low-pass filter module are separate kits.
The synthesiser and one LPF are included with the U3S. Please refer to the separate instructions
for constructing these kits.
Parts placement is defined by the silkscreen printed legend on the PCB, so please observe it carefully,
paying particular attention to the correct orientation of the semiconductors.
The PCB is quite small and the parts are close together. You are recommended to use a low wattage iron
with a fine tip, and fine solder e.g. 1mm diameter or less. Take care not to overheat the PCB and risk
damaging it. A well-lit area and magnifying glass are useful. Be careful not to bridge solder across closely
packed connections. Some of the joints are very close to each other. I recommend checking with a DVM to
make sure no solder bridges have been created.
Note that components D1, Q2, Q3, R2, R3, R4 and C7 are not required or supplied in the kit (R2 may be
added by the builder if lower LCD backlight brightness is desired). Q2 and Q3 are not supplied, additional
BS170 transistors may be installed here to increase the output power (see below). IC1 (the
microcontroller) has an IC socket, in case in future you wish to change the microcontroller e.g. for a
firmware upgrade for new features, etc., or in case you wish to program it yourself. Sockets are provided
for the synthesiser module and the low-pass-filter module.
4.2 Construction steps
Please refer to the parts placement diagram below.
Pay special attention to the orientation of the semiconductors. For IC1, the dimple in the PCB silkscreen
must be aligned with the dimple at the top of the IC socket and the IC.
The order of construction is not important. However, a good principle to follow is to install the smaller
components first, so that the larger ones do not prevent easy access. One suggested order of construction
is described below. I recommend following it carefully.
4
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