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SW+ Project Build - Stage 4 The Product Detector/BFO & Crystal Filter

Build instructions by Paul M0BMN

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Stage 4 The Product Detector/BFO & Crystal Filter

Here we will be working on the second part of the receiver section first find the following part out ready to fit


Only One in this stage

R1 which is 330 Ohm Marked Orange-Orange-Brown

Capacitors Next

C12 270pf Ceramic Disk marked 271J or 271
C13 270pf as above
C14 270pf as above
C15 270pf as above
C16 LINK Use a off cut of wire to fit here , C16 not used but needs linking
C17 68pf Ceramic Disk Marked 68J or 68
C18 150pf Ceramic Disk Marked 151J or 151
C104 0.01uF Ceramic Disk Marked 103M or 103
C105 0.01uF as above

Now The Semiconductors

Only two in this stage

D2 which is a Glass brown body Diode

U3 NE612 or NE602 8 pin IC and its 8 Pin Socket (Fit the socket first of course!)

Last parts

4 off Crystals Marked ECS V 8.00 -S (Yes i know you have five but this stage only needs 4 of them)

right off we go, we will fit the one resistor first

R1, look at the instructions that came with the kit for its location.(Check its value with your meter)

Now onto the Capacitors

start at C12 and work through till C105

Take note that C16 is now replaced by a link wire, just use a off cut from one of the other parts

Now you should have a board that looks like this

Photograph of PCB showing filter capacitors

Note the wire link in C16's place

Now we will fit the Diode and The socket for U3

Make sure that you fit D2 the right way round!

Photograph of D2 fitted to the PCB See the band on D2 is on top

Now fit the socket for U3 and then the crystals

The crystals can be damaged by heat so don't take to long to solder these in, a few seconds at most on each leg is all that you
want to spend with the iron, also don't use loads of solder, its not "Bigger the blob better the job!" to much solder can cause a short between the can and the leads on the top of the board, just be careful and all will be well, if you want use your meter to
check for shorts by touching one probe to the top of the crystal and the other to the pins on the crystal, you should not have a
short, if you do use solder sucker or wick to remover the crystal and then clean it up with the wick and refit.

Our board should look like this now,

Photograph of PCB showing the filter crystals and U3 socket fitted

You can fit Chip U3 (NE612) if you wish now or fit it later.

Now one more stage left before we finish the RX section and start of the TX

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