help in making fm transmitter??

[ssng.89]

we were making a fm transmitter from the linkf as follow
http://www.electronics-circuit.com/basic_FM Wireless 3VDC.html
but from the circuit we didnt get the 8turns inductor...so the shopkeeper gave a wire and said to make 8 turns from it....so my question is ..is there any specification to make it in 8 turns(i mean die of the circle and so)??and how to decide the value of the 8 turn inductor in henry from the circuit??

one more thing for antenna he gave a simple looking wire...is ther any specifications for antenna too....
please do reply us....as soon as possible ...so that we can carry on with the process. plzzzzz

 

[duke37]

The coil looks to be about 4mm diameter, put a 4mm drill bit the wrong way round in a hand drill and wind 8 turns. You could get a more accurate estimate by scaling your photo, knowing the size of the transistor. There are equations giving inductance for a specific design (try Wikipedia)
The inductance can be calculated from the equation F=1/(2*pi*(sqrt(L*C))), chose a capacitance of about halfway on your trimmer. The inductance should be not too critical since the frequency can be trimmed over a fairly wide range with the trimmer.
The antenna connection will affect the frequency and I assume that the coil (L2) is there to make the antenna resosnant at a quarter wave.