FM Radio jammer

john January 13, 2010 117 Comments

Description.
Circuit shown here can be used to jam FM radios in its vicinity. The circuit is nothing but a classic single transistor oscillator operating in the VHF region. Working principle of the circuit is very simple and straight forward. Powerful VHF oscillations from the circuit will interfere with the FM signals to nullify it. Jammer circuits like this are illegal in many countries and you must assemble this circuit on your own responsibility. This circuit is intended only for fun and i request you not to misuse it.
Circuit diagram.

FM radio jammer

Notes.

  • For L1 make 6 turns of 16AWG enamelled copper wire on a 9mm plastic former.
  • The circuit can be powered using a 9V PP3 battery.
  • For extended range, use an antenna.
  • A 30cm long wire connected anywhere on the coil will do for the antenna.
  • For better performance, assemble the circuit on a good PCB.

Comments
  • vicky v
    August 19, 2015

    can u pls explian the the operation of the circuit like how the current flows from battery to till the end what is the function of all capacitors and resistors?

  • Ankit
    July 20, 2015

    What is the use of the C2 capacitor, the one with a 6pF capacity?

  • Knue
    May 22, 2015

    Kindly do tell the number of turns and diameter of the inductor

  • Nsabitanga deo
    April 28, 2015

    1.How long area does this radio jammer circuit can affect?
    2.This circuit is connected into receiver or it work alone?

  • Phil
    March 11, 2015

    spacing between the turns?

  • December 23, 2014

    please send ur final report I am in doing final project to complete my class

    • January 22, 2015

      please send me ur finale project on fm jammer

  • Nobody2014
    October 2, 2014

    I could find 14awg wire… so how many turns will it require?
    ? please reply soon
    thank you

  • sudipto biswas
    August 18, 2014

    sir can you provide me a circuit for jamming mobile phone….. i.e the GSM frequency band..

  • Sanjay
    July 11, 2014

    Where connected earphone in this circuit

    • Reality
      August 8, 2014

      Its not a radio receiver. Its a jammer. Like in movies. It doesn’t allow other receivers to work properly.

  • jam
    June 22, 2014

    thing one. where should I connect a probe to measure voltage by oscilloscope? It seems that a frequency depend on where i put the probe. the prove even detects the signal when it is detached from a circuit.
    thing two. even if there is no C and L in tank circuit except wires, the circuit makes oscillation like 200Mhz is it normal?

  • asim
    May 31, 2014

    sir I need its all components description, and how we calculate voltage and current across each component plz plz ,some body guide me plx

  • Bob
    May 29, 2014

    Excellent idea… that those builders who insist on making me listen to their radio as well as their hammering sorted.
    I can take the hammering, just not the unnecessary noise!

  • Hassan
    May 28, 2014

    plZ tell me what is the value of L1???

    • Seetharaman
      May 29, 2014

      Please see the notes for details.
      Hi Rex you can use shortest lead possible for all components in the oscillator stage. Try to wax them such that the winding and the frequency tuned circuit does not vibrate. Connect external antenna to the first turn from the supply end such that antenna should not load the tank circuit heavily. Use regulated supply with proper decoupling.

  • Rex
    January 22, 2014

    Seetharaman, apart from shelding the circuit with a metal casing, please give me more ideas on how to make the frequency stable

  • mike
    January 13, 2014

    Hello again!

    I built it and it works like a charm! To increase power I have to change the 2N2222 with a 2N2219 and replace the power source with a 12V one? And regarding the power, in a few words, how can I calculate the emitted power?
    One last thing. What is the role of C2?

    Have a good day!

    • Seetharaman
      January 13, 2014

      Without C2 the circuit will not oscillate. You cannot calculate easily like total DC power supplied to the circuit divided by 2 or 3. as it requires many parameters to be calculated, you require like VSWR meter etc.

  • mike
    January 11, 2014

    Hello!

    I’d like to ask something about the capacitors. C4 is an electrolytic (polarized) capacitor and it must be installed the proper way, but what about C3 and C2? Can they be ceramic (without any concern for polarization)? Also, I couldn’t find a 6pF for C2. Is 6.8pF OK?

    Thanks!

    • Seetharaman
      January 11, 2014

      Yes you are correct about C4 C3 and C2. You can use the nearest standard value 6.8PF in place of C2 instead of 6PF.

  • Chiliman
    January 1, 2014

    Can the signal from the circuit be conected to a power amplifier, and in that case, how?

    • Seetharaman
      January 4, 2014

      Add a one turn coil as secondary to the tank circuit inductor L1 and connect it to an RF power amplifier with suitable tank circuit etc and with a capable power supply.

  • ag
    December 13, 2013

    i have difficulty in finding 6-35pF variable capacitor. my question is can i use two 3-15pF variable capacitor connected in parrallel?

  • November 18, 2013

    It is very interesting and I like this circuit as it is very simple. Can you provide this project kit? What is the cost?

  • IonutC
    October 30, 2013

    ok, I built this on breadboard and it works. I just used a coil a made about a month ago for another schema – 16AWG 100 turns on 20 mm diameter plastic tube. How you do the coil doesn’t seem to matter much because you set the frequency from the capacitor.

  • IonutC
    October 30, 2013

    Hi, if I calculate the values for L and C in order for this circuit to jam frequencies in SHF (GHz) will it do it or do I have to change some other component? Can the transistor sustain a frequency of say 3GHz?

    • Seetharaman
      October 31, 2013

      The circuit has to be totally redesigned the transistor the coil (L1 has to be a bar not a wound one) etc.

  • max
    September 21, 2013

    what is the value of L1. I read thru the comments but didnt see anyone really reply to this question asked a couple of times before. how many milihenry?

  • Ashish
    September 14, 2013

    I want to make a GSM signal jammer can u provide the blue print of it…

  • Rex
    September 11, 2013

    Seetharaman, this jammer circuit will work, but will face one problem, the human body capacitance will damped the oscillation in the tank circuit and it can affect the frequency stability.. How do i connect crystal to stabilise the frequency.. Please help me

    • thatotherguyintheelevator
      September 20, 2013

      if you connect a crystal to the circuit then what ever the crystals frequency is then that is the only frequency that you will be able to jam using this circuit. iF you actually want to still connect a crystal then use a 100MHz on because with the inductor being a coil than the tolerance to the crystal changes to about 97MHz-103MHz (jamming those frequencies only)(tolerance=3%)
      where to connect (using schematic): joint north of 6 pF cap. then add 10 ohm (1% or it will screw up the oscillation) resistor on top of it then crystal then connect other end of crystal to coil. the wire joint that comes from south of trimm cap. and goes right connects to the joint between the crystal and the coil in the situation that i have just described

  • christopher
    August 19, 2013

    Hi everyone

    If you have the values of capacitor and inductor, you will be able to calculate the frequency generate by the oscillator with this operation: Fo = 1/(2*pi*sqrt(L*C)).

  • June 5, 2013

    Please mention the list of Components used? i want to made it as college project.
    Thank you

  • Josh
    May 3, 2013

    how to make it jamm all the commercial FM frequency? please give the schematic to jamm all the frequency because this is my final project for my subject. ASAP please?

  • Rishabh Tripathi
    April 6, 2013

    can i use 2-22pF variable capacitor?

  • Rishabh Tripathi
    April 6, 2013

    please tell me the type of capacitor used (0.01uF, 6pF)
    are these capacitors are ceremic or else?

  • December 22, 2012

    I tried several ways to boost the signal, but without a doubt you are right this is the best one.

  • ARUN GEORGE
    October 11, 2012

    how to make infrared camera jammer

  • Piotr
    August 22, 2012

    Guys I just put this together and IT WORKS !!! I used the exact same parts as listed in this schematic minus the transistor. The substitute I used for the 2N2222 transistor was the BC337, you can find that one commonly. Also instead of a 6pF cap I used a 5.6pF and it still works. You have to pay attention to the trimmer capacitor and turn it using an insulated/non-conductive tool (you can put a plastic bag between the cap and a screwdriver and it´ll still work). The inductor doesn´t have to be super accurate either. The tuning is super sensitive so you have to get used to that too, it takes some time. The trimmer capacitor doesn´t have to be the exact same one, it should just cover its range in terms of capacitance. Hope I cleared some of your questions out … Cheers

    • Muhammad Shahid
      December 19, 2012

      can you tell me please the rule of each component of this circuit

    • rakib
      January 3, 2013

      if I cannot find 16awg wire which alternative can I use? -thanks

    • Sarah
      May 20, 2013

      Can you please tell me what frequency range does this circuit jam? and how can i change it to a certain frequency that i want to jam say 88.8 MHz?
      if could help me i would be very thankful .

  • Nobody
    July 21, 2012

    Why not place 2 varactor diodes face to face in parallel with the tank circuit and pump sawtooth waves (PWM) into that.
    Makes for a really nice jammer that covers a wide swath of area on the band.

  • zeeshan
    July 3, 2012

    can i make a 6 turn coil from jumper wires or internet cable wires???

  • SARMA CH M S
    May 8, 2012

    Sir,
    can we use this circuit as cell phone jammer? I want to make a small gsm signal jammer with a radius of 10mts. can u mail the schematic and parts list to my mail id?

    regards

  • Seetharaman
    May 6, 2012

    Hi Adi the component list you can make a list from the circuit and the notes. As for the function is concerned it is just an oscillator producing a blank carrier, which will beat with the transmitted signal and the demodulated signal at the receiver will not have any audible information except some beating signal.

  • Adi
    May 5, 2012

    Can i have the list of the componentsand also the brief description?

  • Seetharaman
    April 19, 2012

    Hi Bo what for you require 3.5mm jack for jammer are you trying to modulate some signal is it. if it is correct.

  • April 18, 2012

    Hi, If i were to connect a 3.5 jack to the circuit, where would i do that.
    Between C3 and GND ?

  • jonard
    March 1, 2012

    hy im jonardz here in d phil.. can i ask what is the component in the c1? is it a trimmer cap or a variable cap? tnx…

    • March 24, 2013

      in this circuit you can use variable cap

  • Syed
    December 29, 2011

    please need help! i couldnt find 16 awg wire.i m having 4 awg.can some tell to make inductor of 4 awg wire??????????As i hav selected it as my semster project i will have to make presentation in few days!!!!!

  • Syed
    December 29, 2011

    I couldnt find 6pf capacitor.can i use 1pf and 5pf in parallel??plus i m having 4 awg wire will it work???16 awg is difficult to be found.

  • Sreeram S
    December 28, 2011

    Hi I would really like try out this project. Can you send me the components details and working to my email_id sreeramdgr8@gmail.com

  • usman umer
    December 16, 2011

    any body can add me for discussion my email is usmantoday@hotmail.com

  • sam
    October 21, 2011

    hey, can i have the list of components with all the power rating and stuff…i want to make this for my college project….so i would like to have the list of all the componnts with all the specifications ASAP

  • Jayamohan
    August 7, 2011

    Hi,

    can i use 2n2222 plastic case or shd i use metal 2n2222 transister only? please confirm.

    also anyone tried this circuit and is it works fine??

  • Cj
    July 18, 2011

    This device can also jam tv. .

  • kinq
    April 20, 2011

    hi i tried this circuit but..i don t know what really went wrong cos i followed it properly still it did not work out

  • MeeX
    February 27, 2011

    many oscilators but no 50Hz oscilators..?

  • Seetharaman
    December 31, 2010

    Hi friend the inductor is the part of the tuned circuit ( L1 and C1) resonates at the required frequency. The in ductor need not be very accurate.

  • Myself
    December 30, 2010

    Does anyone know how many henries that inductor is? I tired using this: http://www.technick.net/public/code/cp_dpage.php?aiocp_dp=util_inductance_circle with the result being 270 nH. Does it really matter how accurate it is? I’m thinking it’s supposed to act as a small range antenna.

  • Seetharaman
    December 14, 2010

    Hi Raj assemble the above. tune FM radio to a station now switch on the above circuit adjust C1 till the FM station is blanked with the carrier beat.

  • Raj
    December 13, 2010

    how can i start up the experiment

  • Seetharaman
    November 6, 2010

    Hi Arun for increasing the power you read my comment dated 6th june. you cannot jam the entire FM band with a width of 20MHz by this simple device.

  • arun
    November 4, 2010

    how can i block the full fm freequency at atime(88Mhz-108Mhz

  • arun
    November 4, 2010

    how can i increase the range of fm jammer

    • Sarah
      May 20, 2013

      hi if u found an answer for your question i would really like to know.
      thank you

  • Seetharaman
    October 3, 2010

    Hi Bryce they are listed in 4 pages of RS catalog on passivie c omponents. you can visit the following site and deside http://in.rsdelivers.com/catalogue/category/trimmer/3377.aspx?pg=1

  • bryce
    October 2, 2010

    what is the items part number and how do i find it

  • Seetharaman
    September 27, 2010

    Hi Bryce you can try with one of the suppliers

    http://www.cheaponsale.com/d-c116022938019608100-indian_components_sales/
    RS Components & Controls India Limited

  • September 26, 2010

    is indian market the name of the wedsite if not what is the name of the wedsite

  • Seetharaman
    September 19, 2010

    Hi Bryce in the indian market
    Hi Jem it will be suitable for frequencies from 60 to 200MHz.

  • Jem
    September 19, 2010

    heya, thanks alot for the link man, helped out alot, i apreciate the help you’ve given. would it be alright to use the ceramic variable caps they sell also, i’m planning on making a pcb and size matters lol, plus the capacitance more closely matches your design 🙂 also, could this schematic be used with some few tweaks to jam all sorts of frequencies, like cell or AM or anything else?

  • bryce
    September 18, 2010

    where did you get the varaible capacitor

  • Seetharaman
    September 18, 2010

    Hi C1 is a pre set capacitor ( trimmer capacitor) if you cannot get it you can use two length (2 to 3 cms) single strand strand plastic hook up wire and twist them together to achieve 2 to 10PF or so. now expand or compress the coil to achieve the required frequency. http://www.surplussales.com/Variables/VariableTrimmers/VarTrimm5.html

  • Jem
    September 17, 2010

    Alright, thanks for the help, i apreciate it alot, now, i’m just wondering where to get the variable cap, i’ve found out all the different names and corps that manufacture them, but so far all the places i’ve been to haven’t seen or heard of them in about five years 🙁 online is the same, i’ve so far found one site but its over in england, 🙁 and sites or tips you have would be great to circumnavigate this issue, (eg. something else i could use, a site, etc.)

  • seetharaman
    September 13, 2010

    Hi Jem it is common ground, that is earth plane of your antenna. If you donot want earth plane you can leave it and use only the wavelength / 4 whip antenna.
    I have not tried simulation but tried the circuit and it is working alright.

  • Jem
    September 12, 2010

    I’m using this program i found that electronically tests circuits, but its not working 🙁 this is the site

    http://www.falstad.com/circuit/
    you have to have java enabled

  • Jem
    September 12, 2010

    ok thank you, now just one more question, i know what all the components are in this, but i’m having trouble translating in my brain how they all connect, i know it should be all easy because of the blueprint, but like, does the second path coming down south off the 9volt source, is that just another positive, or is that the ground coming back to the batter? and if so why the ground symbol on the bottom, is is a common ground for all the components?

  • seetharaman
    September 12, 2010

    Hi Jem You can use components of 16volt and above. Minimum should be 16 volt. it can be 100volt still safe

  • Jem
    September 11, 2010

    hey, i’m trying to build one of these, and i was wondering, do the components have to be rated for 9 volts? cuz i’m looking for one of those variable trimmer caps and all i’m finding are ones that have a working voltage of 100 🙁

  • seetharaman
    July 25, 2010

    Hi Dishant it is in uH, not readily available and easy to wind air core 8 t0 10 mm id, 6 turns wound with 16 to 18 gauge wire with a gap between each winding of wire thickness.

  • dishant
    July 25, 2010

    hi can u please give me value of L1 in henry?so that i can directly use inductor having that value?

  • ALfred
    July 21, 2010

    Hi.
    And if i want to block the whole fm band 88-108mhz.How will i to do?

  • arivu
    July 20, 2010

    hai friends if want ask any doubt contact the emailid arivueee@gmail.com

  • arivu
    July 20, 2010

    very use fuul

  • seetharaman
    July 5, 2010

    Hi Bryce yes. but if you want to only jam a particular broadcast tune only to that.

  • bryce
    July 4, 2010

    would you have to adjust the Fm radio jammmer’s varaible capacitor every time you changed the station on the radio

  • bryce
    July 2, 2010

    how many uh does the L1 have

  • seetharaman
    June 30, 2010

    Hi Gino L2 is the Tank coil to match antenna. you can use the one similar to L1 and tune it for the maximum radiated power

  • Gino
    June 30, 2010

    i think the configuration of two transistor is momething like that:http://english.cxem.net/radiomic/bug29.php
    T2+T3 do the job for increasing power. I don’t know L2 what is used for!

  • bryce
    June 29, 2010

    what if I connected a fm transmitter to the fm radio jammer would the wireless range change

  • Gino
    June 29, 2010

    How can i increase power? Adding another transistor as Rf amplifier?

  • seetharaman
    June 25, 2010

    Hi Bryce within the house only.(less than 100 feet)

  • June 24, 2010

    what is the wireless range for this circuit

  • seetharaman
    June 23, 2010

    No former self supporting coil, 16 to 18AWG any one can be used.

  • June 22, 2010

    does the L1 have to be a 16 awg wire plastic former just give me a staight up answer.

  • seetharaman
    June 19, 2010

    Hi Bryce it has to be in the range of 3 to 35PF. you can use FM tuner variable capacitor also.

  • bryce
    June 19, 2010

    could I use any varaible capacitor or does it have to be a varaible capacitor that is 6-35 pt

  • seetharaman
    June 14, 2010

    Hi Bryce super enamelled copper wire of 1mm dia is well suited. (16 to 18 AWG)
    If you want to jam that station tune in and jam with jammer.

  • June 13, 2010

    does the L1 have to be 16 awg

  • June 13, 2010

    DOES THE RADIO HAE TO BE ON A CERTAIN STATION

  • seetharaman
    June 10, 2010

    Hi Bryce what capacitor value you have used for C2. It can be upto 10PF ceramic disc, L1 should be 6 to 9mm dia air core with 18SWG super enameled copper wire close wound 5 to 6 turns. set the trimmer C1 at the center.
    once the circuit is assembled keep it close to an FM radio tuned to around 100MHz. now switch on the jammer, with a plastic tool expand the coil axially till a blank carrier is heard in the radio. now your FM radio jammer is ready.

  • June 10, 2010

    why is nt his circuit working when I tested it help me

  • seetharaman
    June 10, 2010

    Hi without emitter resistance the transistor will blow of. Resistance can be a near preferred value. THE JAMMER CAN WORK WITHIN A SMALL COMPOUND ONLY.

  • June 9, 2010

    would 3.9 k=3k and 900 ohms

  • June 9, 2010

    does the circuit parts have to be exsactly right (I cant be a ohm or a uF off)

  • June 9, 2010

    what is the wireless range of the fm radio jammer

  • June 9, 2010

    would the fm radio jammer work without the resistors

  • seetharaman
    June 6, 2010

    Hi Bryce by reducing emitter resistance and providing heat sink to 2N2222 and increasing the supply to 12volt you can achieve your requirement. you can replace 2N2222 with 2N2219 for better power desipation

  • June 5, 2010

    what if you doubles all the capacitors Uf’s and transistors current will the wireless range change

  • salman
    March 26, 2010

    Can Anyone tell me the value of INDUCTOR in henry?or any other compatible inductor..

  • […] Notes. For L1 make 6 turns of 16AWG enamelled copper wire on a 9mm plastic former.The circuit can be powered using a 9V PP3 battery.For extended range, use an antenna.A 30cm long wire connected anywhere on the coil will do for the antenna.For better performance, assemble the circuit on a good PCB. Link – circuitstoday […]

  • December 17, 2009

    The legality of the circuit depends on how and where you use it. It is basically a CW generator so a radio will just pick up silence. It differs little from the little transmitters that allow a CD player to be picked up on a nearby radio. There’s just no input where a mic or CD player could be attached. In most jurisdictions, the limiting factor is SWR. So if it can only be picked up for a few meters, the legality would depend on how you use it. If you’re only interfering with your own radio, it should be alright in most places. If you’re intentionally interfering with other peoples’ radios, then it’s illegal almost everywhere.

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