Elektor TAPIR Podręcznik budowy - Strona 9

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The antennas

Now you need to make two antennas, each of which is suitable for a particular

type of field: an E-field antenna for sensing electrical fields and an H-field

antenna for sensing magnetic fields.

Start with the E-field antenna. All you need for this is a length of

solid insulated wire. Cut the wire included in the kit in the middle to

obtain two pieces approximately 25 cm long. Take one of these and

form a loop in one end. Cover the tip of the wire at this point with a

piece of heat-shrink tubing or electrical tape (see photo). This

insulates the antenna, so that you can easily use the loop to sniff for

noise on a circuit board.

At the other end of the wire, strip off approximately 3 mm of the

insulation and slide the Cinch connector shell over the wire. Solder

the wire to the centre pin of the Cinch connector. Screw the

connector together and straighten the antenna. The antenna is now finished.

Next comes the H-field antenna. For this you will use the coil. Trim the leads of

the coil to approximately 4 mm. Cut two lengths of wire approximately 5 cm long

and strip their ends. Solder one end of each wire to the Cinch connector and

screw the connector together. If you are using heat-shrink tubing, slide a piece

of tubing over each wire. Then solder the wires to the coil leads (the polarity

does not matter) and insulate the bare wire ends and coil leads. The H-field

antenna is now ready for use.

Bear in mind that when you hold the TAPIR in your hand, your body forms part

of the antenna, which may increase the audible hum level.