Crystal radio evaluation board with Cat’s Whisker,DIY no soldering Germanium

£11.50

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Description

This can be supplied in kit form in lots of 20  or more for scouts, schools  and Ham clubs.

A circuit board which allows experimentation with Crystal radio. The board comes pre soldered and various components are added to the terminal strip. Different germanium diodes can be substituted to compare.

A cat’s whisker and Iron Pyrite crystal is included, other crystals could be substituted. Four inductors are included to cover a wide frequency range, you could also connect an external wound coil or ferrite rod and coil. ( not supplied in this kit).

Inductors Supplied

AM  inductor    1000uH    Brown Black Red                         423KHZ -1.7MHZ

AM  Inductor       470uH   Yellow Violet Brown Silver        600KHZ – 3.6MHZ

HF  Inductor    100uH     Brown Black Brown Silver         1.3MHZ -7.9MHZ

VHF  Inductor      .39uH   Orange White Gold  Black         60MHZ -180MHZ  With on board 18pF capacitor in circuit.

If you want an amplifier for this board please go to poldhuradiokits.com it is listed in the shop and is also suitable for the Poldhu One Tube Radio.

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. A small screwdriver is supplied to build the radio, no soldering required, the basic board is made up. 

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 with Holder

Bag 1

1 x 1 metre earth wire

1 x crocodile clip

Bag 2

4 x inductors  1000uH 470uH  100uH .39uH

1x resistor

1x germanium diode

2 x Link wire

Bag 3

Aerial

Bag 4

Cat,s Whisker and  Iron Pyrites crystal

….………………………………………………………………………………..

1x crystal earpiece – tested

Full Instructions

This can be supplied in kit form in lots of 20  or more for scouts, schools  and Ham clubs

Postage In order to keep the postage to a minimum postage is for untracked unsigned for. I always obtain a certificate of postage for proof of postage and always dispatch within a couple of days. Please leave response so I know you have received the parcel safely. If you require a tracked and signed for parcel I can supply this service for £5 extra please ask for an invoice or add £5 to the postage cost.

Instructions Radio Evaluation Board

Instructions Radio Evaluation Board

To Build a Crystal Radio
There is no need to cut the component legs.
1. Connect a link wire between 2 and 7
2. Connect a link wire between 1 and 5
3. Connect the 82K resistor ( Grey Red Black Red) between 9 and 10
4. Connect the diode, glass component with red yellow band between 6 and 8 – either way around
5. Connect an inductor, start with 470uH – Yellow Violet Brown Silver between 1 and 4 or connect a coil and ferrite rod.
6. Connect an aerial and earth connection to the A and E terminals.
7. Fit a pair of high impedance headphones. ( Not standard ) headphones.
8. Switch the course capacitor in and adjust course inductor for signal.
To test the radio with an amplifier connect a PP3 battery to the terminals at the top of the board, observe the polarity. Plug in the header cable to the amplifier. Turn the amplifier control anti clockwise ( Maximum)

The germanium diode can be left off the board and a Crystal and cats whisker substituted, fit the crystal and Cat’s Whiser into the holder on the board. A valve tube detector board is also available to experiment with low voltage thermionic emissions.

Adjusting the tuning. Use the small screwdriver provided to adjust the variable capacitor on the board. The capacitors rotate continuously from maximum to minimum, then increase again.

You will need to experiment, in some cases just a good earth is all that is required. Metal water pipe is ideal. Signals will usually be stronger in the evening. If selectively is poor and a few stations breaking through together, try shortening the aerial. Experiment with different aerial lengths to obtain the optimum performance in your area. Swapping the earth and aerial wires can sometimes improve reception.
Other inductors can be substituted to cover different frequencies- only AM signals will be received no FM.
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
Four inductors are included, these have been selected for UK AM radio reception and HF AM reception . You will need to experiment for the best results.
1000uH Brown Black Red Silver 430KHZ-1.6MHZ
470uH Yellow Violet Brown 600kHZ – 2.5MHZ
100uH Brown Black Brown 1.4MHZ – 5.6MHZ
.39 uH Orange White Silver Brown 60MHZ- 180MHZ ( with only 18pF capacitor switched in.
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 terminals 1 and 3 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.

Kit of Parts for Radio Evaluation Board
1 x Built Evaluation  board with Holder
Bag 1
1 x 1 metre earth wire
1 x crocodile clip
Bag 2
4 x inductors  1000uH 470uH  100uH 4.7uH
1x resistor
1x germanium diode
2 x Link wire
Bag 3
Aerial
Bag 4
Cat,s Whisker and  Iron Pyrites crystal

For more information and experiments go to www.poldhuradiokits.com

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