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The Kanga Products FOXX-3 20m QRP Transceiver

Assembly Instructions

Stage 1: The audio amplifier

The FOXX-3 audio amplifier is an LM386 integrated circuit, IC1. It has two inputs with separate volume controls, one
for the receiver audio and on for the transmitter sidetone. During transmission a transistor mutes the receiver audio
input. The amplifier’s output drives low power impedance mono or stereo headphones via a 3.5mm jack socket. The
headphones used with personal stereo players are suitable. If a mono jack is used, a small track cut is necessary to
prevent audio signal being short-circuited to ground. See diagram on the following page. Alternatively a 2 pin header
plug and socket (supplied) can be fitted instead of the jack socket.

Referring to the diagrams on the following page, fit and solder the audio amplifier components in the positions
marked on the component side of the board. The electrolytic capacitors C1, C3, C6 and C9 have a negative and a
positive lead and must be connected the correct way round otherwise they may be damaged when power is applied.
The negative lead is shorter as supplied and is marked with a minus (-) sign on the body of the capacitor. This lead
goes through the hole marked with a minus sign and is soldered to the square pad.

Part

Type

Markings

Notes

100Ω

Brown, Black, Brown, Gold

10KΩ

Brown, black, Orange, Gold

10Ω

Brown, Black, Black, Gold

VR1

47KΩ

47K

Gently push the spindles into the

VR2

1KΩ

central holes of these after soldering.

IC Socket

Fit in position marked IC1 with notch

towards lower edge of the board.

100µF

100µF 16v

Electrolytic capacitor - observe polarity

100nF

104

100µF

100µF 16v

Electrolytic capacitor - observe polarity

100nF

104

100nF

104

10µF

10µF 16v

Electrolytic capacitor - observe polarity

100nF

104

10nF

103

100µF

100µF 16v

Electrolytic capacitor - observe polarity

C10

100nF

104

CON1

2-pin plug

Fit with plastic tab near edge of board

CON2

3.5mm Jack socket or 2-pin plug

Use the connector you prefer

IC1

LM386

Fit into IC socket with notch

towards lower edge of board.

It is important to fit CON1 as shown otherwise the power supply connections will be reversed.

Содержание FOXX-3

Страница 1: ...transceiver you will need a pair of headphones 12v DC supply a battery is ideal and antenna a tuning unit for the 20m Band A power meter would be useful to A separate Morse key can be used but a board mounted key is provided The FOXX 3 printed circuit board has been designed to give the constructor a number of choices 1 Enclosure a The board can be fitted into an Altoids mint tin All connections a...

Страница 2: ...egative and a positive lead and must be connected the correct way round otherwise they may be damaged when power is applied The negative lead is shorter as supplied and is marked with a minus sign on the body of the capacitor This lead goes through the hole marked with a minus sign and is soldered to the square pad Part Type Markings Notes R1 100Ω Brown Black Brown Gold R2 10KΩ Brown black Orange ...

Страница 3: ...ume and side tone controls fully clockwise Holding the headphones some distance from your ears touch the upper terminal of the volume control with a metal object such as a screwdriver You should hear a buzzing noise in the headphones assuming you are near a mains supply Now touch the upper terminal of the sidetone control and observe a similar buzzing noise Turn the two spindles fully anticlockwis...

Страница 4: ...y is kept energised by the charge on capacitor C13 If the key remains released for more than about half a second the relay contacts change back to the receive position This time can be adjusted by altering the value of R6 The charge on C15 holds the mute transistor on until the relay contacts have changed over Part Type Markings Notes R4 1KΩ Brown Black Red Gold R5 4k7Ω Yellow Violet Red Gold R6 1...

Страница 5: ...ch The relay should give a click as it pulls in energises Release the key and note that there is a short delay before the relay clicks again as it drops out de energises Now connect the headphones to CON2 Touch the upper terminal of the volume control with a metal object as before and turn the volume control clockwise until the buzzing noise is heard Press the Morse key and observe that the buzzin...

Страница 6: ...ed from the keyed 12v line Its output goes to the second input of the LM386 via a separate volume control VR2 Part Type Markings Notes R9 47KΩ Yellow Violet Orange Gold R10 4K7Ω Yellow Violet Red Gold R11 10KΩ Brown Black Orange Gold R12 10KΩ Brown Black Orange Gold R13 10KΩ Brown Black Orange Gold R14 680Ω Blue Slate Brown Gold R15 4M7Ω Yellow Violet Green Gold C18 10nF 103 C19 10nF 103 C20 10nF ...

Страница 7: ...nnect a Morse key to CON3 unless you have fitted the switch to the board headphones to CON2 and a 12v supply to SK1 Press the Morse key or switch Turn the sidetone control clockwise until a musical note can be heard in the headphones Adjust the volume control to a comfortable level using the sidetone control Release the Morse key and notice that the sidetone stops immediately ...

Страница 8: ...essarily over heating the crystal Resistor R17 determines the collector current of the oscillator transistor the amount of drive applied to the PA transistor and so the output power of the transmitter It is marked AOT Adjust On Test on the board The two terminal pins provided should be pushed through the holes for R17 from the track side of the board and their heads soldered to the copper pads R17...

Страница 9: ...r to middle of its tuning range Turn the Rx offset control VR3 fully clockwise Press and hold the Morse key on the FOXX 3 and re tune the receiver until the pitch of the note is comfortable for reading Morse This is usually between 400 and 800 Hz use the FOXX 3 s sidetone pitch as a guide Release the Morse key and turn the Rx offset control anticlockwise noting the rise in pitch of the signal on t...

Страница 10: ...uld be evenly spaced not over lapping with a gap between the first and last turn as shown Wind these in the direction shown so that the wires line up with the holes in the board When the winding is complete trim the wires to a length of around 10mm measured from the edge of the toroid To tin the end of the wires form a bead of molten solder on the tip of the soldering iron and pass the end of the ...

Страница 11: ...upply to CON1 Press the Morse key and measure the output power This should be between 500 milliwatts and 1 watt The power can be altered by changing R17 the resistor soldered to the pins Reducing the value of R17 will increase the power Do not run the FOXX 3 with a power output above 1 watt It may be necessary to readjust the receiver offset as described in the previous stage ...

Страница 13: ... that it cannot discriminate between station above and below its operating frequency If for example the FOXX 3 s oscillator is tuned to 14 060 000 MHz when in receive mode stations on 14 060 800 MHz and 14 059 200 will both produce 800Hz beat notes in the headphones The FOXX 3 can be operated from any DC supply of 9 to 14 volts It draws around 250mA when transmitting so a small 12 volt sealed acid...

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