Solderless crystal radio kit evaluation board with germanium diode- cats whisker

£11.50

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Description

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Built and shipped from UK – dispatched air mail within 3 days. You will require a good earth connection to realise the best potential from this radio. You will need wire cutters, pliers and a small screwdriver to assemble. 

This is a solderless kit. Components and links  are fitted to the board via the terminal block –  no soldering is required. The kit is ideal for new experimenters to crystal radio or for developing your own design. 

The kit includes everything you need to produce a crystal radio including the  ear piece and indoor aerial. The  kits can be broken down after use and rebuilt, so ideal for groups of students, after school clubs etc. 

A tested Iron Pyrites  “Cats Whisker” type detector is also included so you can compare with a modern germanium diode. The main assembled board has two variable capacitors and the phono socket fitted but extra capacitance can be introduced via the pads on the board. 

Four header pins and power terminal block  on the board can link the board with an amplifier .

A suitable amplifier lead and speaker can be bought seperatly and not included. 

Kit of Parts for Radio Evaluation Board

1 x Built Evaluation  board

Bag 1

1 x 1metre earth wire

1x black wire

4 x crocodile clips

Bag 2

4 x inductors  1000uH 470uH 330uH 100uH

1x resistor

1x germanium diode

1 x Link wire

6 x crimp ends

2 x crocodile clips

4 x metal stand offs

4 x screws

Bag 3

Aerial

Bag 4

Cat,s Whisker Iron Pyrites detector with holder and crystal

….………………………………………………………………………………..

1x crystal earpiece – tested

Solderless Radio Assembly instructions

Solderless Radio Assembly / Evaluation DIY kit

To Build a crystal radio

Crimp ends are provided to fit to the links, a small pair of pliers should be used to attach them. There is no need to cut the wires on the components.

Fit the 82K resistor Grey Red Black Red between 9-10 on con block,
Fit the germanium diode between 6 and 8
Fit the 470uH inductor Yellow Violet Brown between 1-4 on the con. Block ( other inductors are included to increase the frequency range see later -start with this inductor )
Fit a link wire between 1 – 5
Fit a link wire between 2 -10
Connect a crocodile clip to each end of the long green earth wire. Thread the cable through the hole and crimp both the striped wire and insulated wire. Connect a crocodile clip to each end of the black wire, this is used to connect the aerial wire ( Silver wire in bag)
With the screws provided, fit the 4 metal spacers to the large holes on the board.
The radio should work with just a good earth wire. If a stronger signal is required attach the aerial to the “A” pad -use two crocodile clips attached to the short black wire.The aerial and earth wires go to pads A and B, try either way to obtain the best results.
turn the switch to the “IN” position, this connects both the 18pF variable capacitor, adjust both for the station required. There is no stop on the variable capacitors . Connecting an additional vane type variable capacitor across C and D will increase the frequency range of the receiver. This can be connected with crocodile clips on to the pads.
Connect up the high impedance mono earpiece to the phones socket.
Make up the two blue wires for connecting the “Cats Whisker” detector, fit the crocodile clips and the crimp ends.
Experimenting with natural crystals and a Cat’s Whisker.
Remove the germanium diode from 6 and 8 and fit the crystal and “Cat’s Whisker” to the on board holder using the crocodile clips. “ Experiment by moving the whisker to different parts of the crystal.
Fitting an Amplifier ( Not provided in the kit)
Fit a 9 volt battery clip into the Two way terminal block, observe the polarity on the diagram. Red to +. A diode on the board stops any damage from reverse polarity. Plug the 4 way header cable into the board and the amplifier. Ensure that the V+ cables match up. Connect the speaker to the amplifier terminals. Adjust the amplifier potentiometer to proximate mid position. Adjust later for optimum performance. Anticlockwise on the amplifier increases the volume.
Increasing the frequency range
Three inductors are included, these have been selected for UK AM radio reception. Other inductors can be fitted to in crease the frequency range.
Inductor 2 capacitors 1 capacitor
1000uH Brown Black Red
470uH Yellow Violet Brown
330uH Orange orange Brown
100uH Brown Black Brown
Inductor 2 capacitors 1 capacitor
1000uH 830KHZ – 2.5MHZ 1.1MHZ – 3.5MHZ
470uH 1.2MHZ – 36MHZ 1.7MHZ – 5.19MHZ
300uH 1.4MHZ – 4.3MHZ 2MHZ – 6.19MHZ
100uH 2.6MHZ -7.95MHZ 3.75MHZ – 11.25MHZ

Fault Finding If there is no sound, check the earpiece on a powered appliance, sometimes the earpiece will “ lock up “ during transit , especially if subjected to extreams in temperature.
For the radio to work a good earth is required, a water pipe, or earth rod is ideal. A poor earth will result in a very weak or no signal.
If just noise is heard check the inductor connection.
If the selectivity is poor but signal strong – shorted the aerial. For the optimum performance in your area some experimentation will be required.
Experiments Connect an earth and aerial to each end of the 1000uH inductor. Do not fit an earth and aerial to the board.Position this parallel with the fitted 470uH inductor, the signal will be transferred between the two inductors – this is called mutual inductance. This can result in a stronger signal with less loading on the aerial circuit.
Adding extra capacitance between pads C and D with the switch in the “in” position will change the frequency. You can experiment with home made capacitors. You can substitute the inductor with you home made coils on a ferrite rod.

 

If you require further help or information please email;
trevorsmith50@hotmail.com

 

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