Project-A SIMPLE RECEIVER/TRANSISTOR AMPLIFIER

[ScienceBorn]

Wow! I have finally made my device and it is working perfectly well. ELECTRONIC COMPONENTS REQUIRED-enamel coil of about 100turns[36s.w.g), 500pf/0.0005uf variable capacitor,germanium/semi-conductor diode, 0.01uf capacitor, 4.7kilo-ohms resistor, 1uf capacitor, 100kilo-ohms resistor, n-p-n transistor, a headphone, 6volt battery and a aerial antenna of about 50m/500cm. CONNECTION-connect the aerial antenna to 1/3 of the coil starting from the end to count. Take one end of the coiled wire and connect it to the earth such as a water pipe will increase its sensitivity, then straight to one end of the variable capacitor, then take the other end of the coiled wire and connect to the second end of the variable capacitor( creates a resonator). Connent one end of the coiled wire to the two ends of the germanium/semiconductor diode(i used germanium diode) then straight to the 0.01uf capacitor, connect the other end of the wire straight to the other end of the 0.01uf capacitor.connect one end of the wire to one end of the 4.7kilo-ohms resistor and the other end of the wire to the other end of the same resistor.connect one end of the wire(which is connecting with one end of the 4.7kilo-ohms resistor) straight to the two ends of the 1uf capacitor, the 1uf capacitor is then linked with the 100kilo-ohm resistor and the collector of the n-p-n transistor straight to one side of the headphone and straight to the +ve side of the 6volts battery. Remember we only connected one end of the 4.7kilo-ohm resistor to both ends of the 1uf capacitor, if you don't please look up at the process to recur again. Now that we have recurred, connect the other end of the 4.7kilo-ohm resistor to the emitter of the n-p-n transistor straight to the other side of the headphone and then to the -ve side of the 6volts battery.thats is!!! Please guys i need testimonies!.

 

[davenn]

draw and show us a circuit diagram of your receiver

and take a photo of your circuit for us to see

Dave

 

[ScienceBorn]

Thats what i tried to do but my circuit diagram which i sketch couldnt upload on this forum, that was the main reason i wrote down the connections. A help on how to upload my schmatic diagram will be highly appreciated.

 

[KrisBlueNZ]

Make sure it's less than 100 kilobytes (150 kilobytes for JPG images I think). Click "Go Advanced" and click the paper clip icon to get to the Upload dialog.

If the image is too large:
If it's a scan of a drawing, JPG format can be used; load it into an image editor such as Paint.NET (free) and rescale it to make it only as large as necessary to read everything clearly, and adjust the quality setting on JPG export so it's small enough.

If it's a computer-generated diagram, convert to greyscale and/or reduce the colour depth (16 colours is normally enough), and export it in GIF or PNG format.

 

[ScienceBorn]

Thanks alot, i really appreciate your direction kris. thats my schmatic diagram! Have fun guys.

 

[KrisBlueNZ]

Ah yes, a crystal set with an audio amplifier. That will certainly work.

Just out of interest, has anyone tried adding a small DC bias to counter the voltage drop in the detector diode? For example, break the ground connection between C1 and the 4k7 resistor and connect the C1 side to a voltage around 0.1~0.15V above ground, created using a voltage divider from the battery? Or more simply, leave the ground connected, reverse the detector diode, and add a resistor of around 180k from the top of the 4k7 to +6V? This should allow reception of weaker stations, I think, although obviously they would be quieter.

 

[ScienceBorn]

Kris are you talking of replacing the 100kilo ohm resistor with 180kilo ohm?. Breaking the ground connections between C1 and the 4.7k resistor though i have not yet tried it but i think it will increase the signal of the device or what do u think?

 

[KrisBlueNZ]

No, my suggestion is to add a 180k resistor from the top of the 4k7 resistor to the +6V rail and reverse the detector diode. The idea is to pre-bias the diode by about 0.15V so that it will detect signals with an amplitude less than its natural forward voltage, i.e. weak radio stations. I was just asking whether anyone had tried it.

 

[ScienceBorn]

I understand where you are coming from. I have not tried it but hopfully i will, don't know about others.