FM Jammer - Support required.

[jayamohan]

Hi,

Refer the attached FM jammer circuit.

I am trying to build the same. but not able to make it work.

can some one review the sch and tell me is it fine?

I am using the transistor 2N2222a with TO92-3 plastic case.
Also for the 6pF capacitor i am using 4.7pF and 1.15pF in parallel.
For the variable capacitor i am using 6.5-30Pf (variable)/TZB4R300AE10 from Murata.(refer the attached pdf for the same)

For the power supply i am using 9V battery which we normally use for Multi meters.

Kindly let me know is there anyway to make the circuit working please.

Thanks in advance.

Regards
Mohan.

 

[tpetar]

Why You deal with this. Buy quartz at 100MHz put antena 80cm long and give power, and enjoy!

 

[kalyanasv]

Hi,

you have not really specified your "L" value. Compute the requisite L value for 108 and 88Mhz the upper and lower frequencies using f=1/(2pi*sqrt(LC)) and then find a suitable L value probably in micro henries and then see if it works. The circuit building depends on your soldering abilities.

Gut luck

 

[chuckey]

Monitor the current taken by the circuit, it should be 5-10mA. Grasp the coil with your fingers!!! - This will stop it oscillating and the current should rise. if it does not you have a wiring error. Check the voltage across R3, should be 1-2V. If the circuit was oscillating then the problem is the frequency its tuned to. Try squeezing the turns of the coil closer - lowers the frequency, or stretch the coil - raises the frequency. Because there is no modulation, it is difficult to tune a FM radio into it. You really want an old fashioned set that hisses when its not on a station. Tuning into the oscillator will stop the hiss.
Frank

 

[Audioguru]

The circuit is missing an antenna. When an antenna is connected to the collector or emitter of the transistor then the frequency will change due to the capacitance of the antenna. The frequency will also change when something moves toward or away from the antenna and when the battery voltage runs down.