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 By: Radio-Circuits.Com
Radio-Circuits.Coml
 
 
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

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.

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

Simple FM Transmitter Circuits