**BBG - Crystal Controlled FM Transmitter** The Original Circuits Below Were Built and Sold - In The Thousands To Law Enforcement. Their Original Research and Development Cost , By Today's Standards, Would Total - Well Over A Million Dollars.  FM Transmitter Circuit BBG (C) 2012 radio-circuits .com Radio-Circuits.Coml TP1 Transmitter5VT TransmitterDPT Transmitter 150xt TransmitterXMT TransmitterAB1 Transmitter WB1 Transmitter The BBG Transmitter transmits a Whopping - full 1/2 Watt - (Better Than 500MW) of voice modulated FM Narrowband Frequency Modulation. It is normally used by undercover Agents ( Concealed) as a "Body Bug" ) that has no drift, unlike an adjustable FM wideband transmitter. It transmits both sides of the conversation for up to 2 miles away - and is received on a regular scanner in the VHF frequency range of around 150 to 160 Mhz. BBG Transmitter © 2011 By John S. Wilson Jr. john@bugplan.com Parts List: Circuit # BBG - 1/2 Watt Body Bug - Xtal Controlled Resistors: 1/4 Watt R1 = 10K R2 = 1 MEG R3 = 22K R4 = 1 MEG R5 = 22K R6 = 100 Ohm R7 = 10K R8 = 100K R9 = 10K R10 = 150 Ohm R11 = 100K R12 = 10 Ohm R13 = 150 Ohm ( 1/2 Watt Resistor On This One ) R14 = 2.2K R15 = 10 Ohm ( 1/2 Watt Resistor On This One ) R16 = 3.3K R17 = 47 Ohm ( 1/2 Watt Resistor On This One ) Capacitors: - Disc Or Electrolytic ( Electrolytic Shown with +/- ) All Low Voltage C1 = .02 ( Two .01s in Parallel ) C2 = .001 C3 = .01 C4 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C5 = 10 pf C6 = 100 pf C7 = 100 pf C8 = .01 C9 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C10 = .01 C11 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C12 = .01 C13 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C14 = .001 C15 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C16 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C17 = .001 C18 = 4 to 20 Pf Trimmer ( Adjustable ) Small Surface Mount Type C19 = .01 ( SPECIAL CAPACITOR ) There is A Capacitor Connected across R13 that is not shown in the schematic: This cap is a standard .01 Disc Transistors: Q1 and Q2 = PN918 NPN - Digi-key Electronics Q3 = 2N3866 NPN - Digi-key Electronics Q4 = PN2222 NPN - Digi-key Electronics Q5 and Q6 = 2N3866 NPN - Digi-key Electronics VR: NTE-613 Varactor Diode or a suitable replacement like the Digi-Key Electronics MV2107 BATTERY - 9V ON/OFF Switch: Any, On / Off Switch Will Do - connecting the + side of the 9 volt battery to the circuit M1: Small Electret Microphone Element - Digikey Electronics L1: 21 Turns of # 30 Magnet Wire Wound tight on a Digi-key Electronics 3368K-ND Fiber Washer. The Inductance Of This Coil Is .150 uH L2 and L3: 14 Turns of # 24 Magnet Wire Wound tight on a Mouser or Digi-key Electronics 3368K-ND Fiber Washer. The Inductance Of This Coil Is .07 uH Antenna: 18 1/2 Inches of small flexible stranded wire XT: ( CRYSTAL ) I usually build this circuit to operate between 150 to 165 Mhz. The Crystals I use Are The Digi-Key Electronics Barrel Crystals CA-301 Type which cost a couple of bucks per crystal. This circuit uses a X5 Multiplier and then a X2 Multiplier In the Final. Example: If I use a 15 Mhz Barrel Crystal, the frequency at Q4s output is: Xtal X 5 Or: 75 Mhz into Q5. Q5 Multiplies 75 Mhz X 2 for an end frequency out of the final Q6 ( Desired Output Frequency ) of 150.00 Mhz. Virtually any Fundamental Crystal between 14 and 17 Mhz will output a frequency of between 140 to 170 Mhz, if the crystal has a load capacitance of around 18 pf. If you wish to build this transmitter on A custom frequency simply use the X5 X2 formula above and order a custom cut crystal specifying an 18 pf CL. Example: My Customer Desires this transmitter to function at an output frequency of: 158.250 Mhz? ( 1 ) Divide 158.250 times 2. This Equals 79.125 ( 2 ) Divide 79.125 times 5. This Equals 15.825 I would order the crystal at a Fundamental frequency of 15.825 Mhz, tolerance of .001% and a Crystal Load Capacitance of 18 pf. When I tune my transmitter, my output transmit frequency would be: 158.250 Mhz.