This is a DIY KIT you have to solder the components to the board.
This is a six band radio covering 700K to 30MHZ. The radio can be used in two modes. Crystal mode, you will need to provide a pair of crystal earphones ( not Supplied), the power is switched off and you will need an earth connection.
In powered mode the radio is using a single transistor to detect and amplify the signal. The transistor is a Darlington transistor not an IC. Be amazed at the quality and sensitivity from a single transistor.
Tuning is achieved by adjusting the pre-set trimming capacitors, there is also the facility to fit an external vane type variable capacitor if required ( not Supplied). Stations can be preset and selected by moving the shorting tab provided.
Alternatively an external selector switch could be used ( not provide.
A pair of low impedance headphones suitable for powered operation are provided. Also in the kit is an indoor 5 metre aerial and comprehensive instructions.
Everything you see in the picture is provided in the kit.
If you are interested in simple radio then you should find this a fascinating project.
About the Valve tube and what it does.
The tube is not necessary for the function of the radio but is a protective device for long outdoor aerials
The tube valve is back lit with a yellow LED which acts as a power on indicator The tube is a gas arrester and when excessive static voltages are observed across the electrodes the tube is designed to pass excessive voltages “ spikes “, to earth thus protecting equipment. The ionisation of the tube takes place if a spike in excess of 350 volts is seen across the electrodes of the tube. This arrester will not provide protection from DIRECT lightning strikes. It will discharge static charges to keep an antenna from building up a potential to attract lightning You should GROUND your antenna when not in use even if you have a arrester connected to it.
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1N1004 Black diodes x 2
Yellow red bands
Solder R1 82K resistor ( Grey Red Black Red)
Note; before soldering R2 Fit the Low Z headphone socket as a guide, it needs to be positioned inboard a few millimeters to ensure that the socket fits.
Solder R2 100K resistor (Brown Black Black orange)
Solder R3,R4 and R5 Zero ohm Links – single black Band
Note, there are two diodes marked D2 please see diagram above for correct positioning.
Solder D1 and D2 Diodes 1N4001 Black with line. Polarity sensitive follow silk screen These are together in series towards the bottom of board.
Solder D2 Germanium detecting diode. Glass component yellow red bands (any way round) This is near the top of the board see diagram above .
Solder C5 capacitor marked 104 ( any way around- not polarity sensitive)
Solder C6 Electrolytic capacitor 10uF Polarity sensitive -follow silkscreen
Solder Transistor Q1 Follow silk screen
Solder the tuned circuits for the 6 bands. Each band has one inductor and one variable capacitor. Care should be taken with getting the correct inductor with the correct value capacitor. There are 4 the same value and colour (Brown) variable capacitors for band 1 2, 3, 4 . The two brass variable capacitors are for bands 5 and 6. These have been chosen for optimum performance with this particular circuit. You can substitute values for different frequency ranges if required. These components are in a separate bag for convenience.
Band 1 1000 uH 700KHZ – 1.6MHZ (Brown Black Red Silver) 9-50pF cap
Band 2 330uH 1.2MHZ – 2.9MHZ (Orange Orange Brown Silver) 9-50pF cap
Band 3 220uH 1.5MHZ – 3.5MHZ (Red Red Brown Silver ) 9-50 pF cap
Band 4 100uH 1.3MHZ – 5.4MHZ (Brown Black Brown Silver ) 9-50 pF cap
Band 5 47uH 5.4MHZ 16MHZ ( Yellow Violet Black Silver) 2-18pF cap
Band 6 10uH 11MHZ 30 MHZ (brown Black Black Silver ) 2-18pF cap
Solder the two pin headers for the band selection and the external tune circuit.If you want to connect an extra external variable capacitor then it is possible across the external tune pins. This could be useful for the lower bands especially if you want to go below 700KHZ . You will not damage the circuit so you can experiment!
Solder the power on slide switch
Solder the two earphone output jacks. Ensure that the two locating pins on the base of the sockets are located in the holes in the board.
Solder the two 2 x way connecting blocks
Solder the valve base for the arrester tube and the LED this is best done at the same time. Check the flat ( short Lead ) corresponds with the silk screen on board. Led should be just below top of valve base.
Solder the 100K potentiometer for the RF gain control.
Fit the control knob
Fit valve tube if required. Caution wear protective gloves as this is a fragile glass component.
Using the radio as a crystal power free radio.Connect a suitable earth connections, in most cases stations will be heard with just an earth. Experiment with different aerials. Make sure in crystal mode that the RF gain is fully clockwise ( maximum Gain). Swapping the aerial and earth around in some areas may well improve reception.
Fit some high impedance crystal earphones into the crystal socket. Select band 2 or 3 these will always be the strongest signal in this mode. Vary the trimming capacitor to select a station. You can pre-set a station on each band if required.
Power Mode Standard headphones are fitted into the Low Z socket. Switch on slide switch with battery connected. The LED should light, if not check polarity. Use the band selection in the normal way, use without the crystal earphones plugged in. In power mode the transistor is doing both the detecting and amplification, the germanium diode is out of circuit.
HF reception. In the higher frequency range experiment with and without an earth. Sometimes stronger signals will swamp weaker signals.
Connecting an external tuning capacitor A two pin header is fitted if you want to fit a large external variable capacitor for the four lower bands. The frequency ranges will be effected but provided the external capacitor can go reasonable low the overall frequency range should be covered.
About the Valve tube and what it does.
The tube is not necessary for the function of the radio but is a protective device for long outdoor aerials.The tube is a gas arrester and when excessive static voltages are observed across the electrodes the tube is designed to pass excessive voltages “ spikes “, to earth thus protecting equipment. The ionisation of the tube takes place if a spike in excess of 350 volts is seen across the electrodes of the tube. This arrester will not provide protection from DIRECT lightning strikes. It will discharge static charges to keep an antenna from building up a potential to attract lightning You should GROUND your antenna when not in use even if you have a arrester connected to it.
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